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+## -*- tcl -*-
+# # ## ### ##### ######## ############# #####################
+## Copyright (c) 2007-2008 Andreas Kupries.
+#
+# This software is licensed as described in the file LICENSE, which
+# you should have received as part of this distribution.
+#
+# This software consists of voluntary contributions made by many
+# individuals.  For exact contribution history, see the revision
+# history and logs, available at http://fossil-scm.hwaci.com/fossil
+# # ## ### ##### ######## ############# #####################
+
+## Revisions per project, aka Changesets. These objects are first used
+## in pass 5, which creates the initial set covering the repository.
+
+# # ## ### ##### ######## ############# #####################
+## Requirements
+
+package require Tcl 8.4                               ; # Required runtime.
+package require snit                                  ; # OO system.
+package require struct::set                           ; # Set operations.
+package require vc::tools::misc                       ; # Text formatting
+package require vc::tools::trouble                    ; # Error reporting.
+package require vc::tools::log                        ; # User feedback.
+package require vc::fossil::import::cvs::state        ; # State storage.
+package require vc::fossil::import::cvs::integrity    ; # State integrity checks.
+
+# # ## ### ##### ######## ############# #####################
+##
+
+snit::type ::vc::fossil::import::cvs::project::rev {
+    # # ## ### ##### ######## #############
+    ## Public API
+
+    constructor {project cstype srcid items {theid {}}} {
+	if {$theid ne ""} {
+	    set myid $theid
+	} else {
+	    set myid [incr mycounter]
+	}
+
+	integrity assert {
+	    [info exists mycstype($cstype)]
+	} {Bad changeset type '$cstype'.}
+
+	set myproject   $project
+	set mytype      $cstype
+	set mytypeobj   ::vc::fossil::import::cvs::project::rev::${cstype}
+	set mysrcid	$srcid
+	set myitems     $items
+	set mypos       {} ; # Commit location is not known yet.
+
+	foreach iid $items { lappend mytitems [list $cstype $iid] }
+
+	# Keep track of the generated changesets and of the inverse
+	# mapping from items to them.
+	lappend mychangesets   $self
+	lappend mytchangesets($cstype) $self
+	set     myidmap($myid) $self
+
+	MapItems $cstype $items
+	return
+    }
+
+    destructor {
+	# We may be able to get rid of this entirely, at least for
+	# (de)construction and pass InitCSets.
+
+	UnmapItems $mytype $myitems
+	unset myidmap($myid)
+
+	set pos                    [lsearch -exact $mychangesets $self]
+	set mychangesets           [lreplace       $mychangesets $pos $pos]
+	set pos                    [lsearch -exact $mytchangesets($mytype) $self]
+	set mytchangesets($mytype) [lreplace       $mytchangesets($mytype) $pos $pos]
+	return
+    }
+
+    method str {} {
+	set str    "<"
+	set detail ""
+	if {[$mytypeobj bysymbol]} {
+	    set detail " '[state one {
+		SELECT S.name
+		FROM   symbol S
+		WHERE  S.sid = $mysrcid
+	    }]'"
+	}
+	append str "$mytype ${myid}${detail}>"
+	return $str
+    }
+
+    method lod {} {
+	return [$mytypeobj cs_lod $mysrcid $myitems]
+    }
+
+    method id    {} { return $myid }
+    method items {} { return $mytitems }
+    method data  {} { return [list $myproject $mytype $mysrcid] }
+
+    delegate method bysymbol   to mytypeobj
+    delegate method byrevision to mytypeobj
+    delegate method isbranch   to mytypeobj
+    delegate method istag      to mytypeobj
+
+    method setpos {p} { set mypos $p ; return }
+    method pos    {}  { return $mypos }
+
+    method determinesuccessors {} {
+	# Pass 6 operation. Compute project-level dependencies from
+	# the file-level data and save it back to the state. This may
+	# be called during the cycle breaker passes as well, to adjust
+	# the successor information of changesets which are the
+	# predecessors of dropped changesets. For them we have to
+	# remove their existing information first before inserting the
+	# new data.
+	state run {
+	    DELETE FROM cssuccessor WHERE cid = $myid;
+	}
+	set loop 0
+	# TODO: Check other uses of cs_sucessors.
+	# TODO: Consider merging cs_sucessor's SELECT with the INSERT here.
+	foreach nid [$mytypeobj cs_successors $myitems] {
+	    state run {
+		INSERT INTO cssuccessor (cid,  nid)
+		VALUES                  ($myid,$nid)
+	    }
+	    if {$nid == $myid} { set loop 1 }
+	}
+	# Report after the complete structure has been saved.
+	if {$loop} { $self reportloop }
+	return
+    }
+
+    # result = list (changeset)
+    method successors {} {
+	# Use the data saved by pass 6.
+	return [struct::list map [state run {
+	    SELECT S.nid
+	    FROM   cssuccessor S
+	    WHERE  S.cid = $myid
+	}] [mytypemethod of]]
+    }
+
+    # item -> list (item)
+    method nextmap {} {
+	$mytypeobj successors tmp $myitems
+	return [array get tmp]
+    }
+
+    method breakinternaldependencies {cv} {
+	upvar 1 $cv counter
+	log write 14 csets {[$self str] BID}
+	vc::tools::mem::mark
+
+	# This method inspects the changeset, looking for internal
+	# dependencies. Nothing is done if there are no such.
+
+	# Otherwise the changeset is split into a set of fragments
+	# which have no internal dependencies, transforming the
+	# internal dependencies into external ones. The new changesets
+	# generated from the fragment information are added to the
+	# list of all changesets (by the caller).
+
+	# The code checks only successor dependencies, as this auto-
+	# matically covers the predecessor dependencies as well (Any
+	# successor dependency a -> b is also a predecessor dependency
+	# b -> a).
+
+	array set breaks {}
+
+	set fragments [BreakDirectDependencies $myitems breaks]
+
+	if {![llength $fragments]} { return {} }
+
+	return [$self CreateFromFragments $fragments counter breaks]
+    }
+
+    method persist {} {
+	set tid $mycstype($mytype)
+	set pid [$myproject id]
+	set pos 0
+
+	state transaction {
+	    state run {
+		INSERT INTO changeset (cid,   pid,  type, src)
+		VALUES                ($myid, $pid, $tid, $mysrcid);
+	    }
+
+	    foreach iid $myitems {
+		state run {
+		    INSERT INTO csitem (cid,   pos,  iid)
+		    VALUES             ($myid, $pos, $iid);
+		}
+		incr pos
+	    }
+	}
+	return
+    }
+
+    method timerange {} { return [$mytypeobj timerange $myitems] }
+
+    method limits {} {
+	struct::list assign [$mytypeobj limits $myitems] maxp mins
+	return [list [TagItemDict $maxp $mytype] [TagItemDict $mins $mytype]]
+    }
+
+    method drop {} {
+	log write 8 csets {Dropping $self = [$self str]}
+
+	state transaction {
+	    state run {
+		DELETE FROM changeset   WHERE cid = $myid;
+		DELETE FROM csitem      WHERE cid = $myid;
+		DELETE FROM cssuccessor WHERE cid = $myid;
+	    }
+	}
+
+	# Return the list of predecessors so that they can be adjusted.
+	return [struct::list map [state run {
+	    SELECT cid
+	    FROM   cssuccessor
+	    WHERE  nid = $myid
+	}] [mytypemethod of]]
+    }
+
+    method reportloop {{kill 1}} {
+	# We print the items which are producing the loop, and how.
+
+	set hdr "Self-referential changeset [$self str] __________________"
+	set ftr [regsub -all {[^ 	]} $hdr {_}]
+
+	log write 0 csets $hdr
+	foreach {item nextitem} [$mytypeobj loops $myitems] {
+	    # Create tagged items from the id and our type.
+	    set item     [list $mytype  $item]
+	    set nextitem [list $mytype $nextitem]
+	    # Printable labels.
+	    set i  "<[$type itemstr $item]>"
+	    set n  "<[$type itemstr $nextitem]>"
+	    set ncs $myitemmap($nextitem)
+	    # Print
+	    log write 0 csets {* $i --> $n --> cs [$ncs str]}
+	}
+	log write 0 csets $ftr
+
+	if {!$kill} return
+	trouble internal "[$self str] depends on itself"
+	return
+    }
+
+    method pushto {repository date rstate} {
+	# Generate and import the manifest for this changeset.
+	#
+	# Data needed:
+	# - Commit message               (-- mysrcid -> repository meta)
+	# - User doing the commit        (s.a.)
+	#
+	# - Timestamp of when committed  (command argument)
+	#
+	# - The parent changeset, if any. If there is no parent fossil
+	#   will use the empty base revision as parent.
+	#
+	# - List of the file revisions in the changeset.
+
+	# We derive the lod information directly from the revisions of
+	# the changeset, as the branch part of the meta data (s.a.) is
+	# outdated since pass FilterSymbols. See the method 'run' in
+	# file "c2f_pfiltersym.tcl" for more commentary on this.
+
+	set lodname [$self lod]
+
+	log write 2 csets {Importing changeset [$self str] on $lodname}
+
+	if {[$mytypeobj istag]} {
+	    # Handle tags. They appear immediately after the revision
+	    # they are attached to (*). We can assume that the
+	    # workspace for the relevant line of development
+	    # exists. We retrieve it, then the uuid of the last
+	    # revision entered into it, then tag this revision.
+
+	    # (*) Immediately in terms of the relevant line of
+	    #     development. Revisions on other lines may come in
+	    #     between, but they do not matter to that.
+
+	    set lws  [Getworkspace $rstate $lodname $myproject 0]
+	    set uuid [lindex [$lws getid] 1]
+
+	    $repository tag $uuid [state one {
+		SELECT S.name
+		FROM   symbol S
+		WHERE  S.sid = $mysrcid
+	    }]
+
+	} elseif {[$mytypeobj isbranch]} {
+
+	    # Handle branches. They appear immediately after the
+	    # revision they are spawned from (*). We can assume that
+	    # the workspace for the relevant line of development
+	    # exists.
+
+	    # We retrieve it, then the uuid of the last revision
+	    # entered into it. That revision is tagged as the root of
+	    # the branch (**). A new workspace for the branch is
+	    # created as well, for the future revisions of the new
+	    # line of development.
+
+	    # An exception is made of the non-trunk default branch,
+	    # aka vendor branch. This lod has to have a workspace not
+	    # inherited from anything else. It has no root either, so
+	    # tagging is out as well.
+
+	    # (*) Immediately in terms of the relevant line of
+	    #     development. Revisions on other lines may come in
+	    #     between, but they do not matter to that.
+
+	    # (**) Tagging the parent revision of the branch as its
+	    #      root is done to let us know about the existence of
+	    #      the branch even if it has no revisions committed to
+	    #      it, and thus no regular branch tag anywhere else.
+	    #      The name of the tag is the name for the lod, with
+	    #      the suffix '-root' appended to it.
+
+	    # LOD is self symbol of branch, not parent
+	    set lodname [state one {
+		SELECT S.name
+		FROM   symbol S
+		WHERE  S.sid = $mysrcid
+	    }]
+
+	    if {![$rstate has :trunk:]} {
+		# No trunk implies default branch. Just create the
+		# proper workspace.
+		Getworkspace $rstate $lodname $myproject 1
+	    } else {
+		# Non-default branch. Need workspace, and tag parent
+		# revision.
+
+		set lws [Getworkspace $rstate $lodname $myproject 0]
+		set uuid [lindex [$lws getid] 1]
+
+		$repository tag $uuid ${lodname}-root
+	    }
+	} else {
+	    # Revision changeset.
+
+	    struct::list assign [$myproject getmeta $mysrcid] __ __ user message
+
+	    # Perform the import. As part of that we determine the
+	    # parent we need, and convert the list of items in the
+	    # changeset into uuids and printable data.
+
+	    struct::list assign [Getisdefault $myitems] \
+		isdefault lastdefaultontrunk
+
+	    log write 8 csets {LOD    '$lodname'}
+	    log write 8 csets { def?  $isdefault}
+	    log write 8 csets { last? $lastdefaultontrunk}
+
+	    set lws  [Getworkspace    $rstate $lodname $myproject $isdefault]
+	    $lws add [Getrevisioninfo $myitems]
+
+	    struct::list assign \
+		[$repository importrevision [$self str] \
+		     $user $message $date \
+		     [lindex [$lws getid] 0] [$lws get]] \
+		rid uuid
+
+	    if {[$lws ticks] == 1} {
+		# First commit on this line of development. Set our
+		# own name as a propagating tag. And if the LOD has a
+		# parent we have to prevent the propagation of that
+		# tag into this new line.
+
+		set plws [$lws parent]
+		if {$plws ne ""} {
+		    $repository branchcancel $uuid [$plws name]
+		}
+		$repository branchmark $uuid [$lws name]
+	    }
+
+	    # Remember the imported changeset in the state, under our
+	    # LOD. And if it is the last trunk changeset on the vendor
+	    # branch then the revision is also the actual root of the
+	    # :trunk:, so we remember it as such in the state. However
+	    # if the trunk already exists then the changeset cannot be
+	    # on it any more. This indicates weirdness in the setup of
+	    # the vendor branch, but one we can work around.
+
+	    $lws defid [list $rid $uuid]
+	    if {$lastdefaultontrunk} {
+		log write 2 csets {This cset is the last on the NTDB, set the trunk workspace up}
+
+		if {[$rstate has :trunk:]} {
+		    log write 2 csets {Multiple changesets declared to be the last trunk changeset on the vendor-branch}
+		} else {
+		    $rstate new :trunk: [$lws name]
+		}
+	    }
+	}
+
+	log write 2 csets { }
+	log write 2 csets { }
+	return
+    }
+
+    proc Getrevisioninfo {revisions} {
+	set theset ('[join $revisions {','}]')
+	set revisions {}
+	state foreachrow [subst -nocommands -nobackslashes {
+	    SELECT U.uuid    AS frid,
+	           F.visible AS path,
+	           F.name    AS fname,
+	           R.rev     AS revnr,
+	           R.op      AS rop
+	    FROM   revision R, revuuid U, file F
+	    WHERE  R.rid IN $theset  -- All specified revisions
+	    AND    U.rid = R.rid     -- get fossil uuid of revision
+	    AND    F.fid = R.fid     -- get file of revision
+	}] {
+	    lappend revisions $frid $path $fname/$revnr $rop
+	}
+	return $revisions
+    }
+
+    proc Getworkspace {rstate lodname project isdefault} {
+
+	# The state object holds the workspace state of each known
+	# line-of-development (LOD), up to the last committed
+	# changeset belonging to that LOD.
+
+	# (*) Standard handling if in-LOD changesets. If the LOD of
+	#     the current changeset exists in the state (= has been
+	#     committed to) then this it has the workspace we are
+	#     looking for.
+
+	if {[$rstate has $lodname]} {
+	    return [$rstate get $lodname]
+	}
+
+	# If the LOD is however not yet known, then the current
+	# changeset can be either of
+	# (a) root of a vendor branch,
+	# (b) root of the trunk LOD, or
+	# (c) the first changeset in a new LOD which was spawned from
+	#     an existing LOD.
+
+	# For both (a) and (b) we have to create a new workspace for
+	# the lod, and it doesn't inherit from anything.
+
+	# One exception for (a). If we already have a :vendor: branch
+	# then multiple symbols were used for the vendor branch by
+	# different files. In that case the 'new' branch is made an
+	# alias of the :vendor:, effectively merging the symbols
+	# together.
+
+	# Note that case (b) may never occur. See the variable
+	# 'lastdefaultontrunk' in the caller (method pushto). This
+	# flag can the generation of the workspace for the :trunk: LOD
+	# as well, making it inherit the state of the last
+	# trunk-changeset on the vendor-branch.
+
+	if {$isdefault} {
+	    if {![$rstate has ":vendor:"]} {
+		# Create the vendor branch if not present already. We
+		# use the actual name for the lod, and additional make
+		# it accessible under an internal name (:vendor:) so
+		# that we can merge to it later, should it become
+		# necessary. See the other branch below.
+		$rstate new $lodname
+		$rstate dup :vendor: <-- $lodname
+	    } else {
+		# Merge the new symbol to the vendor branch
+		$rstate dup $lodname <-- :vendor:
+	    }
+	    return [$rstate get $lodname]
+	}
+
+	if {$lodname eq ":trunk:"} {
+	    return [$rstate new $lodname]
+	}
+
+	# Case (c). We find the parent LOD of our LOD and let the new
+	# workspace inherit from the parent's workspace.
+
+	set plodname [[[$project getsymbol $lodname] parent] name]
+
+	log write 8 csets {pLOD   '$plodname'}
+
+	if {[$rstate has $plodname]} {
+	    return [$rstate new $lodname $plodname]
+	}
+
+	foreach k [lsort [$rstate names]] {
+	    log write 8 csets {    $k = [[$rstate get $k] getid]}
+	}
+
+	trouble internal {Unable to determine changeset parent}
+	return
+    }
+
+    proc Getisdefault {revisions} {
+	set theset ('[join $revisions {','}]')
+
+	struct::list assign [state run [subst -nocommands -nobackslashes {
+	    SELECT R.isdefault, R.dbchild
+	    FROM   revision R
+	    WHERE  R.rid IN $theset  -- All specified revisions
+	    LIMIT 1
+	}]] def last
+
+	# TODO/CHECK: look for changesets where isdefault/dbchild is
+	# ambigous.
+
+	return [list $def [expr {$last ne ""}]]
+    }
+
+    typemethod split {cset args} {
+	# As part of the creation of the new changesets specified in
+	# ARGS as sets of items, all subsets of CSET's item set, CSET
+	# will be dropped from all databases, in and out of memory,
+	# and then destroyed.
+	#
+	# Note: The item lists found in args are tagged items. They
+	# have to have the same type as the changeset, being subsets
+	# of its items. This is checked in Untag1.
+
+	log write 8 csets {OLD: [lsort [$cset items]]}
+	ValidateFragments $cset $args
+
+	# All checks pass, actually perform the split.
+
+	struct::list assign [$cset data] project cstype cssrc
+
+	set predecessors [$cset drop]
+	$cset destroy
+
+	set newcsets {}
+	foreach fragmentitems $args {
+	    log write 8 csets {MAKE: [lsort $fragmentitems]}
+
+	    set fragment [$type %AUTO% $project $cstype $cssrc \
+			      [Untag $fragmentitems $cstype]]
+	    lappend newcsets $fragment
+
+	    $fragment persist
+	    $fragment determinesuccessors
+	}
+
+	# The predecessors have to recompute their successors, i.e.
+	# remove the dropped changeset and put one of the fragments
+	# into its place.
+	foreach p $predecessors {
+	    $p determinesuccessors
+	}
+
+	return $newcsets
+    }
+
+    typemethod itemstr {item} {
+	struct::list assign $item itype iid
+	return [$itype str $iid]
+    }
+
+    typemethod strlist {changesets} {
+	return [join [struct::list map $changesets [myproc ID]]]
+    }
+
+    proc ID {cset} { $cset str }
+
+    proc Untag {taggeditems cstype} {
+	return [struct::list map $taggeditems [myproc Untag1 $cstype]]
+    }
+
+    proc Untag1 {cstype theitem} {
+	struct::list assign $theitem t i
+	integrity assert {$cstype eq $t} {Item $i's type is '$t', expected '$cstype'}
+	return $i
+    }
+
+    proc TagItemDict {itemdict cstype} {
+	set res {}
+	foreach {i v} $itemdict { lappend res [list $cstype $i] $v }
+	return $res
+    }
+
+    proc ValidateFragments {cset fragments} {
+	# Check the various integrity constraints for the fragments
+	# specifying how to split the changeset:
+	#
+	# * We must have two or more fragments, as splitting a
+	#   changeset into one makes no sense.
+	# * No fragment may be empty.
+	# * All fragments have to be true subsets of the items in the
+	#   changeset to split. The 'true' is implied because none are
+	#   allowed to be empty, so each has to be smaller than the
+	#   total.
+	# * The union of the fragments has to be the item set of the
+	#   changeset.
+	# * The fragment must not overlap, i.e. their pairwise
+	#   intersections have to be empty.
+
+	set cover {}
+	foreach fragmentitems $fragments {
+	    log write 8 csets {NEW: [lsort $fragmentitems]}
+
+	    integrity assert {
+		![struct::set empty $fragmentitems]
+	    } {changeset fragment is empty}
+
+	    integrity assert {
+		[struct::set subsetof $fragmentitems [$cset items]]
+	    } {changeset fragment is not a subset}
+	    struct::set add cover $fragmentitems
+	}
+
+	integrity assert {
+	    [struct::set equal $cover [$cset items]]
+	 } {The fragments do not cover the original changeset}
+
+	set i 1
+	foreach fia $fragments {
+	    foreach fib [lrange $fragments $i end] {
+		integrity assert {
+		    [struct::set empty [struct::set intersect $fia $fib]]
+		} {The fragments <$fia> and <$fib> overlap}
+	    }
+	    incr i
+	}
+
+	return
+    }
+
+    # # ## ### ##### ######## #############
+    ## State
+
+    variable myid        {} ; # Id of the cset for the persistent
+			      # state.
+    variable myproject   {} ; # Reference of the project object the
+			      # changeset belongs to.
+    variable mytype      {} ; # What the changeset is based on
+			      # (revisions, tags, or branches).
+			      # Values: See mycstype. Note that we
+			      # have to keep the names of the helper
+			      # singletons in sync with the contents
+			      # of state table 'cstype', and various
+			      # other places using them hardwired.
+    variable mytypeobj   {} ; # Reference to the container for the
+			      # type dependent code. Derived from
+			      # mytype.
+    variable mysrcid     {} ; # Id of the metadata or symbol the cset
+			      # is based on.
+    variable myitems     {} ; # List of the file level revisions,
+			      # tags, or branches in the cset, as
+			      # ids. Not tagged.
+    variable mytitems    {} ; # As myitems, the tagged form.
+    variable mypos       {} ; # Commit position of the changeset, if
+			      # known.
+
+    # # ## ### ##### ######## #############
+    ## Internal methods
+
+    typevariable mycounter        0 ; # Id counter for csets. Last id
+				      # used.
+    typevariable mycstype -array {} ; # Map cstypes (names) to persistent
+				      # ids. Note that we have to keep
+				      # the names in the table 'cstype'
+				      # in sync with the names of the
+				      # helper singletons.
+
+    typemethod inorder {projectid} {
+	# Return all changesets (object references) for the specified
+	# project, in the order given to them by the sort passes. Both
+	# the filtering by project and the sorting by time make the
+	# use of 'project::rev rev' impossible.
+
+	set res {}
+	state foreachrow {
+	    SELECT C.cid  AS xcid,
+	           T.date AS cdate
+	    FROM   changeset C, cstimestamp T
+	    WHERE  C.pid  = $projectid -- limit to changesets in project
+	    AND    T.cid  = C.cid      -- get ordering information
+	    ORDER BY T.date            -- sort into commit order
+	} {
+	    lappend res $myidmap($xcid) $cdate
+	}
+	return $res
+    }
+
+    typemethod getcstypes {} {
+	state foreachrow {
+	    SELECT tid, name FROM cstype;
+	} { set mycstype($name) $tid }
+	return
+    }
+
+    typemethod load {repository} {
+	set n 0
+	log write 2 csets {Loading the changesets}
+	state foreachrow {
+	    SELECT C.cid   AS id,
+	           C.pid   AS xpid,
+                   CS.name AS cstype,
+	           C.src   AS srcid
+	    FROM   changeset C, cstype CS
+	    WHERE  C.type = CS.tid
+	    ORDER BY C.cid
+	} {
+	    log progress 2 csets $n {}
+	    set r [$type %AUTO% [$repository projectof $xpid] $cstype $srcid [state run {
+		SELECT C.iid
+		FROM   csitem C
+		WHERE  C.cid = $id
+		ORDER BY C.pos
+	    }] $id]
+	    incr n
+	}
+	return
+    }
+
+    typemethod loadcounter {} {
+	# Initialize the counter from the state
+	log write 2 csets {Loading changeset counter}
+	set mycounter [state one { SELECT MAX(cid) FROM changeset }]
+	return
+    }
+
+    typemethod num {} { return $mycounter }
+
+    # # ## ### ##### ######## #############
+
+    method CreateFromFragments {fragments cv bv} {
+	upvar 1 $cv counter $bv breaks
+	UnmapItems $mytype $myitems
+
+	# Create changesets for the fragments, reusing the current one
+	# for the first fragment. We sort them in order to allow
+	# checking for gaps and nice messages.
+
+	set newcsets  {}
+	set fragments [lsort -index 0 -integer $fragments]
+
+	#puts \t.[join [PRs $fragments] .\n\t.].
+
+	Border [lindex $fragments 0] firsts firste
+
+	integrity assert {
+	    $firsts == 0
+	} {Bad fragment start @ $firsts, gap, or before beginning of the range}
+
+	set laste $firste
+	foreach fragment [lrange $fragments 1 end] {
+	    Border $fragment s e
+	    integrity assert {
+		$laste == ($s - 1)
+	    } {Bad fragment border <$laste | $s>, gap or overlap}
+
+	    set new [$type %AUTO% $myproject $mytype $mysrcid [lrange $myitems $s $e]]
+	    lappend newcsets $new
+	    incr counter
+
+            log write 4 csets {Breaking [$self str ] @ $laste, new [$new str], cutting $breaks($laste)}
+
+	    set laste $e
+	}
+
+	integrity assert {
+	    $laste == ([llength $myitems]-1)
+	} {Bad fragment end @ $laste, gap, or beyond end of the range}
+
+	# Put the first fragment into the current changeset, and
+	# update the in-memory index. We can simply (re)add the items
+	# because we cleared the previously existing information, see
+	# 'UnmapItems' above. Persistence does not matter here, none
+	# of the changesets has been saved to the persistent state
+	# yet.
+
+	set myitems  [lrange $myitems  0 $firste]
+	set mytitems [lrange $mytitems 0 $firste]
+	MapItems $mytype $myitems
+	return $newcsets
+    }
+
+    # # ## ### ##### ######## #############
+
+    proc BreakDirectDependencies {theitems bv} {
+	upvar 1 mytypeobj mytypeobj self self $bv breaks
+
+	# Array of dependencies (parent -> child). This is pulled from
+	# the state, and limited to successors within the changeset.
+
+	array set dependencies {}
+
+	$mytypeobj internalsuccessors dependencies $theitems
+	if {![array size dependencies]} {
+	    return {}
+	} ; # Nothing to break.
+
+	log write 5 csets ...[$self str].......................................................
+	vc::tools::mem::mark
+
+	return [BreakerCore $theitems dependencies breaks]
+    }
+
+    proc BreakerCore {theitems dv bv} {
+	# Break a set of revisions into fragments which have no
+	# internal dependencies.
+
+	# We perform all necessary splits in one go, instead of only
+	# one. The previous algorithm, adapted from cvs2svn, computed
+	# a lot of state which was thrown away and then computed again
+	# for each of the fragments. It should be easier to update and
+	# reuse that state.
+
+	upvar 1 $dv dependencies $bv breaks
+
+	# We have internal dependencies to break. We now iterate over
+	# all positions in the list (which is chronological, at least
+	# as far as the timestamps are correct and unique) and
+	# determine the best position for the break, by trying to
+	# break as many dependencies as possible in one go. When a
+	# break was found this is redone for the fragments coming and
+	# after, after upding the crossing information.
+
+	# Data structures:
+	# Map:  POS   revision id      -> position in list.
+	#       CROSS position in list -> number of dependencies crossing it
+	#       DEPC  dependency       -> positions it crosses
+	# List: RANGE Of the positions itself.
+	# Map:  DELTA position in list -> time delta between its revision
+	#                                 and the next, if any.
+	# A dependency is a single-element map parent -> child
+
+	# InitializeBreakState initializes their contents after
+	# upvar'ing them from this scope. It uses the information in
+	# DEPENDENCIES to do so.
+
+	InitializeBreakState $theitems
+
+	set fragments {}
+	set new       [list $range]
+
+	# Instead of one list holding both processed and pending
+	# fragments we use two, one for the framents to process, one
+	# to hold the new fragments, and the latter is copied to the
+	# former when they run out. This keeps the list of pending
+	# fragments short without sacrificing speed by shifting stuff
+	# down. We especially drop the memory of fragments broken
+	# during processing after a short time, instead of letting it
+	# consume memory.
+
+	while {[llength $new]} {
+
+	    set pending $new
+	    set new     {}
+	    set at      0
+
+	    while {$at < [llength $pending]} {
+		set current [lindex $pending $at]
+
+		log write 6 csets {. . .. ... ..... ........ .............}
+		log write 6 csets {Scheduled   [join [PRs [lrange $pending $at end]] { }]}
+		log write 6 csets {Considering [PR $current] \[$at/[llength $pending]\]}
+
+		set best [FindBestBreak $current]
+
+		if {$best < 0} {
+		    # The inspected range has no internal
+		    # dependencies. This is a complete fragment.
+		    lappend fragments $current
+
+		    log write 6 csets "No breaks, final"
+		} else {
+		    # Split the range and schedule the resulting
+		    # fragments for further inspection. Remember the
+		    # number of dependencies cut before we remove them
+		    # from consideration, for documentation later.
+
+		    set breaks($best) $cross($best)
+
+		    log write 6 csets "Best break @ $best, cutting [nsp $cross($best) dependency dependencies]"
+
+		    # Note: The value of best is an abolute location
+		    # in myitems. Use the start of current to make it
+		    # an index absolute to current.
+
+		    set brel [expr {$best - [lindex $current 0]}]
+		    set bnext $brel ; incr bnext
+		    set fragbefore [lrange $current 0 $brel]
+		    set fragafter  [lrange $current $bnext end]
+
+		    log write 6 csets "New pieces  [PR $fragbefore] [PR $fragafter]"
+
+		    integrity assert {[llength $fragbefore]} {Found zero-length fragment at the beginning}
+		    integrity assert {[llength $fragafter]}  {Found zero-length fragment at the end}
+
+		    lappend new $fragbefore $fragafter
+		    CutAt $best
+		}
+
+		incr at
+	    }
+	}
+
+	log write 6 csets ". . .. ... ..... ........ ............."
+
+	return $fragments
+    }
+
+    proc InitializeBreakState {revisions} {
+	upvar 1 pos pos cross cross range range depc depc delta delta \
+	    dependencies dependencies
+
+	# First we create a map of positions to make it easier to
+	# determine whether a dependency crosses a particular index.
+
+	log write 14 csets {IBS: #rev [llength $revisions]}
+	log write 14 csets {IBS: pos map, cross counter}
+
+	array set pos   {}
+	array set cross {}
+	array set depc  {}
+	set range       {}
+	set n 0
+	foreach rev $revisions {
+	    lappend range $n
+	    set pos($rev) $n
+	    set cross($n) 0
+	    incr n
+	}
+
+	log write 14 csets {IBS: pos/[array size pos], cross/[array size cross]}
+
+	# Secondly we count the crossings per position, by iterating
+	# over the recorded internal dependencies.
+
+	# Note: If the timestamps are badly out of order it is
+	#       possible to have a backward successor dependency,
+	#       i.e. with start > end. We may have to swap the indices
+	#       to ensure that the following loop runs correctly.
+	#
+	# Note 2: start == end is not possible. It indicates a
+	#         self-dependency due to the uniqueness of positions,
+	#         and that is something we have ruled out already, see
+	#         'rev internalsuccessors'.
+
+	log write 14 csets {IBS: cross counter filling, pos/cross map}
+
+	foreach {rid children} [array get dependencies] {
+	    foreach child $children {
+		set dkey    [list $rid $child]
+		set start   $pos($rid)
+		set end     $pos($child)
+
+		if {$start > $end} {
+		    set crosses [list $end [expr {$start-1}]]
+		    while {$end < $start} {
+			incr cross($end)
+			incr end
+		    }
+		} else {
+		    set crosses [list $start [expr {$end-1}]]
+		    while {$start < $end} {
+			incr cross($start)
+			incr start
+		    }
+		}
+		set depc($dkey) $crosses
+	    }
+	}
+
+	log write 14 csets {IBS: pos/[array size pos], cross/[array size cross], depc/[array size depc] (for [llength $revisions])}
+	log write 14 csets {IBS: timestamps, deltas}
+
+	InitializeDeltas $revisions
+
+	log write 14 csets {IBS: delta [array size delta]}
+	return
+    }
+
+    proc InitializeDeltas {revisions} {
+	upvar 1 delta delta
+
+	# Pull the timestamps for all revisions in the changesets and
+	# compute their deltas for use by the break finder.
+
+	array set delta {}
+	array set stamp {}
+
+	set theset ('[join $revisions {','}]')
+	state foreachrow [subst -nocommands -nobackslashes {
+	    SELECT R.rid AS xrid, R.date AS time
+	    FROM revision R
+	    WHERE R.rid IN $theset
+	}] {
+	    set stamp($xrid) $time
+	}
+
+	log write 14 csets {IBS: stamp [array size stamp]}
+
+	set n 0
+	foreach rid [lrange $revisions 0 end-1] rnext [lrange $revisions 1 end] {
+	    set delta($n) [expr {$stamp($rnext) - $stamp($rid)}]
+	    incr n
+	}
+	return
+    }
+
+    proc FindBestBreak {range} {
+	upvar 1 cross cross delta delta
+
+	# Determine the best break location in the given range of
+	# positions. First we look for the locations with the maximal
+	# number of crossings. If there are several we look for the
+	# shortest time interval among them. If we still have multiple
+	# possibilities after that we select the earliest location
+	# among these.
+
+	# Note: If the maximal number of crossings is 0 then the range
+	#       has no internal dependencies, and no break location at
+	#       all. This possibility is signaled via result -1.
+
+	# Note: A range of length 1 or less cannot have internal
+	#       dependencies, as that needs at least two revisions in
+	#       the range.
+
+	if {[llength $range] < 2} { return -1 }
+
+	set max -1
+	set best {}
+
+	foreach location $range {
+	    set crossings $cross($location)
+	    if {$crossings > $max} {
+		set max  $crossings
+		set best [list $location]
+		continue
+	    } elseif {$crossings == $max} {
+		lappend best $location
+	    }
+	}
+
+	if {$max == 0}            { return -1 }
+	if {[llength $best] == 1} { return [lindex $best 0] }
+
+	set locations $best
+	set best {}
+	set min -1
+
+	foreach location $locations {
+	    set interval $delta($location)
+	    if {($min < 0) || ($interval < $min)} {
+		set min  $interval
+		set best [list $location]
+	    } elseif {$interval == $min} {
+		lappend best $location
+	    }
+	}
+
+	if {[llength $best] == 1} { return [lindex $best 0] }
+
+	return [lindex [lsort -integer -increasing $best] 0]
+    }
+
+    proc CutAt {location} {
+	upvar 1 cross cross depc depc
+
+	# It was decided to split the changeset at the given
+	# location. This cuts a number of dependencies. Here we update
+	# the cross information so that the break finder has accurate
+	# data when we look at the generated fragments.
+
+	set six [log visible? 6]
+
+	# Note: The loop below could be made faster by keeping a map
+	# from positions to the dependencies crossing. An extension of
+	# CROSS, i.e. list of dependencies, counter is implied. Takes
+	# a lot more memory however, and takes time to update here
+	# (The inner loop is not incr -1, but ldelete).
+
+	foreach dep [array names depc] {
+	    set range $depc($dep)
+	    # Check all dependencies still known, take their range and
+	    # see if the break location falls within.
+
+	    Border $range s e
+	    if {$location < $s} continue ; # break before range, ignore
+	    if {$location > $e} continue ; # break after range, ignore.
+
+	    # This dependency crosses the break location. We remove it
+	    # from the crossings counters, and then also from the set
+	    # of known dependencies, as we are done with it.
+
+	    Border $depc($dep) ds de
+	    for {set loc $ds} {$loc <= $de} {incr loc} {
+		incr cross($loc) -1
+	    }
+	    unset depc($dep)
+
+	    if {!$six} continue
+
+	    struct::list assign $dep parent child
+	    log write 5 csets "Broke dependency [PD $parent] --> [PD $child]"
+	}
+
+	return
+    }
+
+    # Print identifying data for a revision (project, file, dotted rev
+    # number), for high verbosity log output.
+    # TODO: Replace with call to itemstr (list rev $id)
+
+    proc PD {id} {
+	foreach {p f r} [state run {
+		SELECT P.name , F.name, R.rev
+		FROM revision R, file F, project P
+		WHERE R.rid = $id    -- Find specified file revision
+		AND   F.fid = R.fid  -- Get file of the revision
+		AND   P.pid = F.pid  -- Get project of the file.
+	}] break
+	return "'$p : $f/$r'"
+    }
+
+    # Printing one or more ranges, formatted, and only their border to
+    # keep the strings short.
+
+    proc PRs {ranges} {
+	return [struct::list map $ranges [myproc PR]]
+    }
+
+    proc PR {range} {
+	Border $range s e
+	return <${s}...${e}>
+    }
+
+    proc Border {range sv ev} {
+	upvar 1 $sv s $ev e
+	set s [lindex $range 0]
+	set e [lindex $range end]
+	return
+    }
+
+    # # ## ### ##### ######## #############
+
+    proc UnmapItems {thetype theitems} {
+	# (*) We clear out the associated part of the myitemmap
+	# in-memory index in preparation for new data, or as part of
+	# object destruction. A simple unset is enough, we have no
+	# symbol changesets at this time, and thus never more than one
+	# reference in the list.
+
+	upvar 1 myitemmap myitemmap self self
+	foreach iid $theitems {
+	    set key [list $thetype $iid]
+	    unset myitemmap($key)
+	    log write 8 csets {MAP- item <$key> $self = [$self str]}
+	}
+	return
+    }
+
+    proc MapItems {thetype theitems} {
+	upvar 1 myitemmap myitemmap self self
+
+	foreach iid $theitems {
+	    set key [list $thetype $iid]
+	    set myitemmap($key) $self
+	    log write 8 csets {MAP+ item <$key> $self = [$self str]}
+	}
+	return
+    }
+
+    # # ## ### ##### ######## #############
+
+    typevariable mychangesets         {} ; # List of all known
+					   # changesets.
+
+    # List of all known changesets of a type.
+    typevariable mytchangesets -array {
+	sym::branch {}
+	sym::tag    {}
+	rev         {}
+    }
+
+    typevariable myitemmap     -array {} ; # Map from items (tagged)
+					   # to the list of changesets
+					   # containing it. Each item
+					   # can be used by only one
+					   # changeset.
+    typevariable myidmap   -array {} ; # Map from changeset id to
+				       # changeset.
+
+    typemethod all    {}    { return $mychangesets }
+    typemethod of     {cid} { return $myidmap($cid) }
+    typemethod ofitem {iid} { return $myitemmap($iid) }
+
+    typemethod rev    {}    { return $mytchangesets(rev) }
+    typemethod sym    {}    { return [concat \
+					  ${mytchangesets(sym::branch)} \
+					  ${mytchangesets(sym::tag)}] }
+
+    # # ## ### ##### ######## #############
+    ## Configuration
+
+    pragma -hastypeinfo    no  ; # no type introspection
+    pragma -hasinfo        no  ; # no object introspection
+
+    # # ## ### ##### ######## #############
+}
+
+##
+## NOTE: The successor and predecessor methods defined by the classes
+##       below are -- bottle necks --. Look for ways to make the SQL
+##       faster.
+##
+
+# # ## ### ##### ######## ############# #####################
+## Helper singleton. Commands for revision changesets.
+
+snit::type ::vc::fossil::import::cvs::project::rev::rev {
+    typemethod byrevision {} { return 1 }
+    typemethod bysymbol   {} { return 0 }
+    typemethod istag      {} { return 0 }
+    typemethod isbranch   {} { return 0 }
+
+    typemethod str {revision} {
+	struct::list assign [state run {
+	    SELECT R.rev, F.name, P.name
+	    FROM   revision R, file F, project P
+	    WHERE  R.rid = $revision -- Find specified file revision
+	    AND    F.fid = R.fid     -- Get file of the revision
+	    AND    P.pid = F.pid     -- Get project of the file.
+	}] revnr fname pname
+	return "$pname/${revnr}::$fname"
+    }
+
+    # result = list (mintime, maxtime)
+    typemethod timerange {items} {
+	set theset ('[join $items {','}]')
+	return [state run [subst -nocommands -nobackslashes {
+	    SELECT MIN(R.date), MAX(R.date)
+	    FROM revision R
+	    WHERE R.rid IN $theset -- Restrict to revisions of interest
+	}]]
+    }
+
+    # var(dv) = dict (revision -> list (revision))
+    typemethod internalsuccessors {dv revisions} {
+	upvar 1 $dv dependencies
+	set theset ('[join $revisions {','}]')
+
+	log write 14 csets internalsuccessors
+
+	# See 'successors' below for the main explanation of
+	# the various cases. This piece is special in that it
+	# restricts the successors we look for to the same set of
+	# revisions we start from. Sensible as we are looking for
+	# changeset internal dependencies.
+
+	array set dep {}
+
+	state foreachrow [subst -nocommands -nobackslashes {
+    -- (1) Primary child
+	    SELECT R.rid AS xrid, R.child AS xchild
+	    FROM   revision R
+	    WHERE  R.rid   IN $theset     -- Restrict to revisions of interest
+	    AND    R.child IS NOT NULL    -- Has primary child
+	    AND    R.child IN $theset     -- Which is also of interest
+    UNION
+    -- (2) Secondary (branch) children
+	    SELECT R.rid AS xrid, B.brid AS xchild
+	    FROM   revision R, revisionbranchchildren B
+	    WHERE  R.rid   IN $theset     -- Restrict to revisions of interest
+	    AND    R.rid = B.rid          -- Select subset of branch children
+	    AND    B.brid IN $theset      -- Which is also of interest
+    UNION
+    -- (4) Child of trunk root successor of last NTDB on trunk.
+	    SELECT R.rid AS xrid, RA.child AS xchild
+	    FROM revision R, revision RA
+	    WHERE R.rid   IN $theset      -- Restrict to revisions of interest
+	    AND   R.isdefault             -- Restrict to NTDB
+	    AND   R.dbchild IS NOT NULL   -- and last NTDB belonging to trunk
+	    AND   RA.rid = R.dbchild      -- Go directly to trunk root
+	    AND   RA.child IS NOT NULL    -- Has primary child.
+            AND   RA.child IN $theset     -- Which is also of interest
+	}] {
+	    # Consider moving this to the integrity module.
+	    integrity assert {$xrid != $xchild} {Revision $xrid depends on itself.}
+	    lappend dependencies($xrid) $xchild
+	    set dep($xrid,$xchild) .
+	}
+
+	# The sql statements above looks only for direct dependencies
+	# between revision in the changeset. However due to the
+	# vagaries of meta data it is possible for two revisions of
+	# the same file to end up in the same changeset, without a
+	# direct dependency between them. However we know that there
+	# has to be a an indirect dependency, be it through primary
+	# children, branch children, or a combination thereof.
+
+	# We now fill in these pseudo-dependencies, if no such
+	# dependency exists already. The direction of the dependency
+	# is actually irrelevant for this.
+
+	# NOTE: This is different from cvs2svn. Our spiritual ancestor
+	# does not use such pseudo-dependencies, however it uses a
+	# COMMIT_THRESHOLD, a time interval commits should fall. This
+	# will greatly reduces the risk of getting far separated
+	# revisions of the same file into one changeset.
+
+	# We allow revisions to be far apart in time in the same
+	# changeset, but in turn need the pseudo-dependencies to
+	# handle this.
+
+	log write 14 csets {internal  [array size dep]}
+	log write 14 csets {collected [array size dependencies]}
+	log write 14 csets pseudo-internalsuccessors
+
+	array set fids {}
+	state foreachrow [subst -nocommands -nobackslashes {
+	    SELECT R.rid AS xrid, R.fid AS xfid
+            FROM   revision R
+            WHERE  R.rid IN $theset
+	}] { lappend fids($xfid) $xrid }
+
+	set groups {}
+	foreach {fid rids} [array get fids] {
+	    if {[llength $rids] < 2} continue
+	    foreach a $rids {
+		foreach b $rids {
+		    if {$a == $b} continue
+		    if {[info exists dep($a,$b)]} continue
+		    if {[info exists dep($b,$a)]} continue
+		    lappend dependencies($a) $b
+		    set dep($a,$b) .
+		    set dep($b,$a) .
+		}
+	    }
+	    set n [llength $rids]
+	    lappend groups [list $n [expr {($n*$n-$n)/2}]]
+	}
+
+	log write 14 csets {pseudo    [array size fids] ([lsort -index 0 -decreasing -integer $groups])}
+	log write 14 csets {internal  [array size dep]}
+	log write 14 csets {collected [array size dependencies]}
+	log write 14 csets complete
+	return
+    }
+
+    # result = 4-list (itemtype itemid nextitemtype nextitemid ...)
+    typemethod loops {revisions} {
+	# Note: Tags and branches cannot cause the loop. Their id's,
+	# being of a fundamentally different type than the revisions
+	# coming in cannot be in the set.
+
+	set theset ('[join $revisions {','}]')
+	return [state run [subst -nocommands -nobackslashes {
+	    -- (1) Primary child
+	    SELECT R.rid, R.child
+	    FROM   revision R
+	    WHERE  R.rid   IN $theset     -- Restrict to revisions of interest
+	    AND    R.child IS NOT NULL    -- Has primary child
+	    AND    R.child IN $theset     -- Loop
+	    --
+	    UNION
+	    -- (2) Secondary (branch) children
+	    SELECT R.rid, B.brid
+	    FROM   revision R, revisionbranchchildren B
+	    WHERE  R.rid   IN $theset     -- Restrict to revisions of interest
+	    AND    R.rid = B.rid          -- Select subset of branch children
+	    AND    B.rid   IN $theset     -- Loop
+	    --
+	    UNION
+	    -- (4) Child of trunk root successor of last NTDB on trunk.
+	    SELECT R.rid, RA.child
+	    FROM   revision R, revision RA
+	    WHERE  R.rid    IN $theset     -- Restrict to revisions of interest
+	    AND    R.isdefault             -- Restrict to NTDB
+	    AND    R.dbchild IS NOT NULL   -- and last NTDB belonging to trunk
+	    AND    RA.rid = R.dbchild      -- Go directly to trunk root
+	    AND    RA.child IS NOT NULL    -- Has primary child.
+	    AND    RA.child IN $theset     -- Loop
+	}]]
+    }
+
+    # var(dv) = dict (item -> list (item)), item  = list (type id)
+    typemethod successors {dv revisions} {
+	upvar 1 $dv dependencies
+	set theset ('[join $revisions {','}]')
+
+	# The following cases specify when a revision S is a successor
+	# of a revision R. Each of the cases translates into one of
+	# the branches of the SQL UNION coming below.
+	#
+	# (1) S can be a primary child of R, i.e. in the same LOD. R
+	#     references S directly. R.child = S(.rid), if it exists.
+	#
+	# (2) S can be a secondary, i.e. branch, child of R. Here the
+	#     link is made through the helper table
+	#     REVISIONBRANCHCHILDREN. R.rid -> RBC.rid, RBC.brid =
+	#     S(.rid)
+	#
+	# (3) Originally this use case defined the root of a detached
+	#     NTDB as the successor of the trunk root. This leads to a
+	#     bad tangle later on. With a detached NTDB the original
+	#     trunk root revision was removed as irrelevant, allowing
+	#     the nominal root to be later in time than the NTDB
+	#     root. Now setting this dependency will be backward in
+	#     time. REMOVED.
+	#
+	# (4) If R is the last of the NTDB revisions which belong to
+	#     the trunk, then the primary child of the trunk root (the
+	#     '1.2' revision) is a successor, if it exists.
+
+	# Note that the branches spawned from the revisions, and the
+	# tags associated with them are successors as well.
+
+	state foreachrow [subst -nocommands -nobackslashes {
+    -- (1) Primary child
+	    SELECT R.rid AS xrid, R.child AS xchild
+	    FROM   revision R
+	    WHERE  R.rid   IN $theset     -- Restrict to revisions of interest
+	    AND    R.child IS NOT NULL    -- Has primary child
+    UNION
+    -- (2) Secondary (branch) children
+	    SELECT R.rid AS xrid, B.brid AS xchild
+	    FROM   revision R, revisionbranchchildren B
+	    WHERE  R.rid   IN $theset     -- Restrict to revisions of interest
+	    AND    R.rid = B.rid          -- Select subset of branch children
+    UNION
+    -- (4) Child of trunk root successor of last NTDB on trunk.
+	    SELECT R.rid AS xrid, RA.child AS xchild
+	    FROM revision R, revision RA
+	    WHERE R.rid   IN $theset      -- Restrict to revisions of interest
+	    AND   R.isdefault             -- Restrict to NTDB
+	    AND   R.dbchild IS NOT NULL   -- and last NTDB belonging to trunk
+	    AND   RA.rid = R.dbchild      -- Go directly to trunk root
+	    AND   RA.child IS NOT NULL    -- Has primary child.
+	}] {
+	    # Consider moving this to the integrity module.
+	    integrity assert {$xrid != $xchild} {Revision $xrid depends on itself.}
+	    lappend dependencies([list rev $xrid]) [list rev $xchild]
+	}
+	state foreachrow [subst -nocommands -nobackslashes {
+	    SELECT R.rid AS xrid, T.tid AS xchild
+	    FROM   revision R, tag T
+	    WHERE  R.rid IN $theset       -- Restrict to revisions of interest
+	    AND    T.rev = R.rid          -- Select tags attached to them
+	}] {
+	    lappend dependencies([list rev $xrid]) [list sym::tag $xchild]
+	}
+	state foreachrow [subst -nocommands -nobackslashes {
+	    SELECT R.rid AS xrid, B.bid AS xchild
+	    FROM   revision R, branch B
+	    WHERE  R.rid IN $theset       -- Restrict to revisions of interest
+	    AND    B.root = R.rid         -- Select branches attached to them
+	}] {
+	    lappend dependencies([list rev $xrid]) [list sym::branch $xchild]
+	}
+	return
+    }
+
+    # result = list (changeset-id)
+    typemethod cs_successors {revisions} {
+        # This is a variant of 'successors' which maps the low-level
+        # data directly to the associated changesets. I.e. instead
+        # millions of dependency pairs (in extreme cases (Example: Tcl
+        # CVS)) we return a very short and much more manageable list
+        # of changesets.
+
+	set theset ('[join $revisions {','}]')
+	return [state run [subst -nocommands -nobackslashes {
+    -- (1) Primary child
+	    SELECT C.cid
+	    FROM   revision R, csitem CI, changeset C
+	    WHERE  R.rid   IN $theset     -- Restrict to revisions of interest
+	    AND    R.child IS NOT NULL    -- Has primary child
+            AND    CI.iid = R.child       -- Select all changesets
+            AND    C.cid = CI.cid         -- containing the primary child
+            AND    C.type = 0             -- which are revision changesets
+    UNION
+    -- (2) Secondary (branch) children
+	    SELECT C.cid
+	    FROM   revision R, revisionbranchchildren B, csitem CI, changeset C
+	    WHERE  R.rid   IN $theset     -- Restrict to revisions of interest
+	    AND    R.rid = B.rid          -- Select subset of branch children
+            AND    CI.iid = B.brid        -- Select all changesets
+            AND    C.cid = CI.cid	  -- containing the branch
+            AND    C.type = 0		  -- which are revision changesets
+    UNION
+    -- (4) Child of trunk root successor of last NTDB on trunk.
+	    SELECT C.cid
+	    FROM   revision R, revision RA, csitem CI, changeset C
+	    WHERE  R.rid   IN $theset      -- Restrict to revisions of interest
+	    AND    R.isdefault             -- Restrict to NTDB
+	    AND    R.dbchild IS NOT NULL   -- and last NTDB belonging to trunk
+	    AND    RA.rid = R.dbchild      -- Go directly to trunk root
+	    AND    RA.child IS NOT NULL    -- Has primary child.
+            AND    CI.iid = RA.child       -- Select all changesets
+            AND    C.cid = CI.cid	   -- containing the primary child
+            AND    C.type = 0		   -- which are revision changesets
+    UNION
+	    SELECT C.cid
+	    FROM   revision R, tag T, csitem CI, changeset C
+	    WHERE  R.rid in $theset        -- Restrict to revisions of interest
+	    AND    T.rev = R.rid	   -- Select tags attached to them
+            AND    CI.iid = T.tid          -- Select all changesets
+            AND    C.cid = CI.cid	   -- containing the tags
+            AND    C.type = 1		   -- which are tag changesets
+    UNION
+	    SELECT C.cid
+	    FROM   revision R, branch B, csitem CI, changeset C
+	    WHERE  R.rid in $theset        -- Restrict to revisions of interest
+	    AND    B.root = R.rid	   -- Select branches attached to them
+            AND    CI.iid = B.bid          -- Select all changesets
+            AND    C.cid = CI.cid	   -- containing the branches
+            AND    C.type = 2		   -- which are branch changesets
+	}]]
+
+	# Regarding rev -> branch|tag, we could consider looking at
+	# the symbol of the branch|tag, its lod-symbol, and the
+	# revisions on that lod, but don't. Because it is not exact
+	# enough, the branch|tag would depend on revisions coming
+	# after its creation on the parental lod.
+    }
+
+    # result = symbol name
+    typemethod cs_lod {metaid revisions} {
+	# Determines the name of the symbol which is the line of
+	# development for the revisions in a changeset. The
+	# information in the meta data referenced by the source metaid
+	# is out of date by the time we come here (since pass
+	# FilterSymbols), so it cannot be used. See the method 'run'
+	# in file "c2f_pfiltersym.tcl" for more commentary on this.
+
+	set theset ('[join $revisions {','}]')
+	return [state run [subst -nocommands -nobackslashes {
+	    SELECT
+	    DISTINCT L.name
+	    FROM   revision R, symbol L
+	    WHERE  R.rid in $theset        -- Restrict to revisions of interest
+	    AND    L.sid = R.lod           -- Get lod symbol of revision
+	}]]
+    }
+}
+
+# # ## ### ##### ######## ############# #####################
+## Helper singleton. Commands for tag symbol changesets.
+
+snit::type ::vc::fossil::import::cvs::project::rev::sym::tag {
+    typemethod byrevision {} { return 0 }
+    typemethod bysymbol   {} { return 1 }
+    typemethod istag      {} { return 1 }
+    typemethod isbranch   {} { return 0 }
+
+    typemethod str {tag} {
+	struct::list assign [state run {
+	    SELECT S.name, F.name, P.name
+	    FROM   tag T, symbol S, file F, project P
+	    WHERE  T.tid = $tag   -- Find specified tag
+	    AND    F.fid = T.fid  -- Get file of tag
+	    AND    P.pid = F.pid  -- Get project of file
+	    AND    S.sid = T.sid  -- Get symbol of tag
+	}] sname fname pname
+	return "$pname/T'${sname}'::$fname"
+    }
+
+    # result = list (mintime, maxtime)
+    typemethod timerange {tags} {
+	# The range is defined as the range of the revisions the tags
+	# are attached to.
+
+	set theset ('[join $tags {','}]')
+	return [state run [subst -nocommands -nobackslashes {
+	    SELECT MIN(R.date), MAX(R.date)
+	    FROM   tag T, revision R
+	    WHERE  T.tid IN $theset  -- Restrict to tags of interest
+            AND    R.rid = T.rev     -- Select tag parent revisions
+	}]]
+    }
+
+    # var(dv) = dict (item -> list (item)), item  = list (type id)
+    typemethod successors {dv tags} {
+	# Tags have no successors.
+	return
+    }
+
+    # result = 4-list (itemtype itemid nextitemtype nextitemid ...)
+    typemethod loops {tags} {
+	# Tags have no successors, therefore cannot cause loops
+	return {}
+    }
+
+    # result = list (changeset-id)
+    typemethod cs_successors {tags} {
+	# Tags have no successors.
+	return
+    }
+
+    # result = symbol name
+    typemethod cs_lod {sid tags} {
+	# Determines the name of the symbol which is the line of
+	# development for the tags in a changeset. Comes directly from
+	# the symbol which is the changeset's source and its prefered
+	# parent.
+
+        return [state run {
+ 	    SELECT P.name
+	    FROM preferedparent SP, symbol P
+	    WHERE SP.sid = $sid
+	    AND   P.sid = SP.pid
+	}]
+    }
+}
+
+# # ## ### ##### ######## ############# #####################
+## Helper singleton. Commands for branch symbol changesets.
+
+snit::type ::vc::fossil::import::cvs::project::rev::sym::branch {
+    typemethod byrevision {} { return 0 }
+    typemethod bysymbol   {} { return 1 }
+    typemethod istag      {} { return 0 }
+    typemethod isbranch   {} { return 1 }
+
+    typemethod str {branch} {
+	struct::list assign [state run {
+	    SELECT S.name, F.name, P.name
+	    FROM   branch B, symbol S, file F, project P
+	    WHERE  B.bid = $branch  -- Find specified branch
+	    AND    F.fid = B.fid    -- Get file of branch
+	    AND    P.pid = F.pid    -- Get project of file
+	    AND    S.sid = B.sid    -- Get symbol of branch
+	}] sname fname pname
+	return "$pname/B'${sname}'::$fname"
+    }
+
+    # result = list (mintime, maxtime)
+    typemethod timerange {branches} {
+	# The range of a branch is defined as the range of the
+	# revisions the branches are spawned by. NOTE however that the
+	# branches associated with a detached NTDB will have no root
+	# spawning them, hence they have no real timerange any
+	# longer. By using 0 we put them in front of everything else,
+	# as they logically are.
+
+	set theset ('[join $branches {','}]')
+	return [state run [subst -nocommands -nobackslashes {
+	    SELECT IFNULL(MIN(R.date),0), IFNULL(MAX(R.date),0)
+	    FROM  branch B, revision R
+	    WHERE B.bid IN $theset   -- Restrict to branches of interest
+            AND   R.rid = B.root     -- Select branch parent revisions
+	}]]
+    }
+
+    # result = 4-list (itemtype itemid nextitemtype nextitemid ...)
+    typemethod loops {branches} {
+	# Note: Revisions and tags cannot cause the loop. Being of a
+	# fundamentally different type they cannot be in the incoming
+	# set of ids.
+
+	set theset ('[join $branches {','}]')
+	return [state run [subst -nocommands -nobackslashes {
+	    SELECT B.bid, BX.bid
+	    FROM   branch B, preferedparent P, branch BX
+	    WHERE  B.bid IN $theset   -- Restrict to branches of interest
+	    AND    B.sid = P.pid      -- Get the prefered branches via
+	    AND    BX.sid = P.sid     -- the branch symbols
+	    AND    BX.bid IN $theset  -- Loop
+	}]]
+    }
+
+    # var(dv) = dict (item -> list (item)), item  = list (type id)
+    typemethod successors {dv branches} {
+	upvar 1 $dv dependencies
+	# The first revision committed on a branch, and all branches
+	# and tags which have it as their prefered parent are the
+	# successors of a branch.
+
+	set theset ('[join $branches {','}]')
+	state foreachrow [subst -nocommands -nobackslashes {
+	    SELECT B.bid AS xbid, R.rid AS xchild
+	    FROM   branch B, revision R
+	    WHERE  B.bid IN $theset     -- Restrict to branches of interest
+	    AND    B.first = R.rid      -- Get first revision on the branch
+	}] {
+	    lappend dependencies([list sym::branch $xbid]) [list rev $xchild]
+	}
+	state foreachrow [subst -nocommands -nobackslashes {
+	    SELECT B.bid AS xbid, BX.bid AS xchild
+	    FROM   branch B, preferedparent P, branch BX
+	    WHERE  B.bid IN $theset     -- Restrict to branches of interest
+	    AND    B.sid = P.pid        -- Get subordinate branches via the
+	    AND    BX.sid = P.sid       -- prefered parents of their symbols
+	}] {
+	    lappend dependencies([list sym::branch $xbid]) [list sym::branch $xchild]
+	}
+	state foreachrow [subst -nocommands -nobackslashes {
+	    SELECT B.bid AS xbid, T.tid AS xchild
+	    FROM   branch B, preferedparent P, tag T
+	    WHERE  B.bid IN $theset     -- Restrict to branches of interest
+	    AND    B.sid = P.pid        -- Get subordinate tags via the
+	    AND    T.sid = P.sid        -- prefered parents of their symbols
+	}] {
+	    lappend dependencies([list sym::branch $xbid]) [list sym::tag $xchild]
+	}
+	return
+    }
+
+    # result = list (changeset-id)
+    typemethod cs_successors {branches} {
+        # This is a variant of 'successors' which maps the low-level
+        # data directly to the associated changesets. I.e. instead
+        # millions of dependency pairs (in extreme cases (Example: Tcl
+        # CVS)) we return a very short and much more manageable list
+        # of changesets.
+
+	set theset ('[join $branches {','}]')
+        return [state run [subst -nocommands -nobackslashes {
+	    SELECT C.cid
+	    FROM   branch B, revision R, csitem CI, changeset C
+	    WHERE  B.bid IN $theset     -- Restrict to branches of interest
+	    AND    B.first = R.rid	-- Get first revision on the branch
+            AND    CI.iid = R.rid       -- Select all changesets
+            AND    C.cid = CI.cid	-- containing this revision
+            AND    C.type = 0		-- which are revision changesets
+    UNION
+	    SELECT C.cid
+	    FROM   branch B, preferedparent P, branch BX, csitem CI, changeset C
+	    WHERE  B.bid IN $theset     -- Restrict to branches of interest
+	    AND    B.sid = P.pid	-- Get subordinate branches via the
+	    AND    BX.sid = P.sid	-- prefered parents of their symbols
+            AND    CI.iid = BX.bid      -- Select all changesets
+            AND    C.cid = CI.cid	-- containing the subordinate branches
+            AND    C.type = 2		-- which are branch changesets
+    UNION
+	    SELECT C.cid
+	    FROM   branch B, preferedparent P, tag T, csitem CI, changeset C
+	    WHERE  B.bid IN $theset     -- Restrict to branches of interest
+	    AND    B.sid = P.pid	-- Get subordinate tags via the
+	    AND    T.sid = P.sid	-- prefered parents of their symbols
+            AND    CI.iid = T.tid       -- Select all changesets
+            AND    C.cid = CI.cid	-- containing the subordinate tags
+            AND    C.type = 1		-- which are tag changesets
+	}]]
+	return
+    }
+
+    # result = symbol name
+    typemethod cs_lod {sid branches} {
+	# Determines the name of the symbol which is the line of
+	# development for the branches in a changeset. Comes directly
+	# from the symbol which is the changeset's source and its
+	# prefered parent.
+
+        return [state run {
+ 	    SELECT P.name
+	    FROM preferedparent SP, symbol P
+	    WHERE SP.sid = $sid
+	    AND   P.sid = SP.pid
+	}]
+    }
+
+    typemethod limits {branches} {
+	# Notes. This method exists only for branches. It is needed to
+	# get detailed information about a backward branch. It does
+	# not apply to tags, nor revisions. The queries can also
+	# restrict themselves to the revision sucessors/predecessors
+	# of branches, as only they have ordering data and thus can
+	# cause the backwardness.
+
+	set theset ('[join $branches {','}]')
+
+	set maxp [state run [subst -nocommands -nobackslashes {
+	    -- maximal predecessor position per branch
+	    SELECT B.bid, MAX (CO.pos)
+	    FROM   branch B, revision R, csitem CI, changeset C, csorder CO
+	    WHERE  B.bid IN $theset     -- Restrict to branches of interest
+	    AND    B.root = R.rid       -- Get branch root revisions
+	    AND    CI.iid = R.rid       -- Get changesets containing the
+	    AND    C.cid = CI.cid       -- root revisions, which are
+	    AND    C.type = 0           -- revision changesets
+	    AND    CO.cid = C.cid       -- Get their topological ordering
+	    GROUP BY B.bid
+	}]]
+
+	set mins [state run [subst -nocommands -nobackslashes {
+	    -- minimal successor position per branch
+	    SELECT B.bid, MIN (CO.pos)
+	    FROM   branch B, revision R, csitem CI, changeset C, csorder CO
+	    WHERE  B.bid IN $theset     -- Restrict to branches of interest
+	    AND    B.first = R.rid      -- Get the first revisions on the branches
+	    AND    CI.iid = R.rid       -- Get changesets containing the
+	    AND    C.cid = CI.cid	-- first revisions, which are
+	    AND    C.type = 0		-- revision changesets
+	    AND    CO.cid = C.cid	-- Get their topological ordering
+	    GROUP BY B.bid
+	}]]
+
+        return [list $maxp $mins]
+    }
+
+    # # ## ### ##### ######## #############
+    ## Configuration
+
+    pragma -hasinstances   no ; # singleton
+    pragma -hastypeinfo    no ; # no introspection
+    pragma -hastypedestroy no ; # immortal
+}
+
+# # ## ### ##### ######## ############# #####################
+##
+
+namespace eval ::vc::fossil::import::cvs::project {
+    namespace export rev
+    namespace eval rev {
+	namespace import ::vc::fossil::import::cvs::state
+	namespace import ::vc::fossil::import::cvs::integrity
+	namespace import ::vc::tools::misc::*
+	namespace import ::vc::tools::trouble
+	namespace import ::vc::tools::log
+	log register csets
+
+	# Set up the helper singletons
+	namespace eval rev {
+	    namespace import ::vc::fossil::import::cvs::state
+	    namespace import ::vc::fossil::import::cvs::integrity
+	    namespace import ::vc::tools::log
+	}
+	namespace eval sym::tag {
+	    namespace import ::vc::fossil::import::cvs::state
+	    namespace import ::vc::fossil::import::cvs::integrity
+	    namespace import ::vc::tools::log
+	}
+	namespace eval sym::branch {
+	    namespace import ::vc::fossil::import::cvs::state
+	    namespace import ::vc::fossil::import::cvs::integrity
+	    namespace import ::vc::tools::log
+	}
+    }
+}
+
+# # ## ### ##### ######## ############# #####################
+## Ready
+
+package provide vc::fossil::import::cvs::project::rev 1.0
+return