Fossil

	    # revision on each branch becomes a new and disconnected
	    # root.

	    foreach branch [$root branches] {
		$branch cutbranchparent
		if {![$branch haschild]} continue
		set first [$branch child]
		$first cutfromparentbranch
		$first cutfromparent
		$branch cutchild
		lappend myroots $first
	    }
	    $root removeallbranches

	    # Tagging a dead revision doesn't do anything, so remove
	    # any tags that were set on it.

	    set branch [$root parentbranch]
	    set parent [$root parent]
	    set child  [$root child]

	    ldelete myroots $root
	    lappend myroots $child

	    $branch cutbranchparent
	    $branch cutchild
	    $child  cutfromparent

	    $branch setchild        $child
	    $child  setparentbranch $branch

	    $parent removebranch        $branch
	    $parent removechildonbranch $root
	}
	return
    }

    method LinesOfDevelopment {} {

	set symbols   {}

	foreach root [$self LinesOfDevelopment] {
	    if {[$root hasparentbranch]} { lappend symbols [$root parentbranch] }
	    while {$root ne ""} {
		lappend revisions $root
		foreach tag    [$root tags]     { lappend symbols $tag    }
		foreach branch [$root branches] { lappend symbols $branch }
		foreach branch [$root branches] {
		    integrity assert {
			[$branch parent] eq $root
		    } {Backreference branch to its root is missing or wrong}
		    lappend symbols $branch
		}
		set lod [$root lod]
		if {![$lod istrunk]} { lappend symbols $lod }
		if {![$lod istrunk]} {
		    integrity assert {
			[$lod haschild]
		    } {Branch is LOD symbol without revisions}
		    lappend symbols $lod
		}
		set root [$root child]
	    }
	}

	return [list [lsort -unique -dict $revisions] [lsort -unique -dict $symbols]]
    }