gitk: Provide ability to highlight based on relationship to selected commit

This provides a way to highlight commits that are, or are not,
descendents or ancestors of the currently selected commit.  It's
still rough around the edges but seems to be useful even so.

Signed-off-by: Paul Mackerras <paulus@samba.org>

gitk

@@ -538,6 +538,15 @@ proc makewindow {} {
     $viewhlmenu conf -font $uifont
     .ctop.top.lbar.vhl conf -font $uifont
     pack .ctop.top.lbar.vhl -side left -fill y
+    label .ctop.top.lbar.rlabel -text " OR " -font $uifont
+    pack .ctop.top.lbar.rlabel -side left -fill y
+    global highlight_related
+    set m [tk_optionMenu .ctop.top.lbar.relm highlight_related None \
+	       "Descendent" "Not descendent" "Ancestor" "Not ancestor"]
+    $m conf -font $uifont
+    .ctop.top.lbar.relm conf -font $uifont
+    trace add variable highlight_related write vrel_change
+    pack .ctop.top.lbar.relm -side left -fill y
 
     panedwindow .ctop.cdet -orient horizontal
     .ctop add .ctop.cdet
@@ -1642,7 +1651,7 @@ proc showview {n} {
 # Stuff relating to the highlighting facility
 
 proc ishighlighted {row} {
-    global vhighlights fhighlights nhighlights
+    global vhighlights fhighlights nhighlights rhighlights
 
     if {[info exists nhighlights($row)] && $nhighlights($row) > 0} {
 	return $nhighlights($row)
@@ -1653,6 +1662,9 @@ proc ishighlighted {row} {
     if {[info exists fhighlights($row)] && $fhighlights($row) > 0} {
 	return $fhighlights($row)
     }
+    if {[info exists rhighlights($row)] && $rhighlights($row) > 0} {
+	return $rhighlights($row)
+    }
     return 0
 }
 
@@ -1925,6 +1937,135 @@ proc askfindhighlight {row id} {
     set nhighlights($row) $isbold
 }
 
+proc vrel_change {name ix op} {
+    global highlight_related
+
+    rhighlight_none
+    if {$highlight_related ne "None"} {
+	after idle drawvisible
+    }
+}
+
+# prepare for testing whether commits are descendents or ancestors of a
+proc rhighlight_sel {a} {
+    global descendent desc_todo ancestor anc_todo
+    global highlight_related rhighlights
+
+    catch {unset descendent}
+    set desc_todo [list $a]
+    catch {unset ancestor}
+    set anc_todo [list $a]
+    if {$highlight_related ne "None"} {
+	rhighlight_none
+	after idle drawvisible
+    }
+}
+
+proc rhighlight_none {} {
+    global rhighlights
+
+    set rows [array names rhighlights]
+    if {$rows ne {}} {
+	unset rhighlights
+	unbolden $rows
+    }
+}
+
+proc is_descendent {a} {
+    global curview children commitrow descendent desc_todo
+
+    set v $curview
+    set la $commitrow($v,$a)
+    set todo $desc_todo
+    set leftover {}
+    set done 0
+    for {set i 0} {$i < [llength $todo]} {incr i} {
+	set do [lindex $todo $i]
+	if {$commitrow($v,$do) < $la} {
+	    lappend leftover $do
+	    continue
+	}
+	foreach nk $children($v,$do) {
+	    if {![info exists descendent($nk)]} {
+		set descendent($nk) 1
+		lappend todo $nk
+		if {$nk eq $a} {
+		    set done 1
+		}
+	    }
+	}
+	if {$done} {
+	    set desc_todo [concat $leftover [lrange $todo [expr {$i+1}] end]]
+	    return
+	}
+    }
+    set descendent($a) 0
+    set desc_todo $leftover
+}
+
+proc is_ancestor {a} {
+    global curview parentlist commitrow ancestor anc_todo
+
+    set v $curview
+    set la $commitrow($v,$a)
+    set todo $anc_todo
+    set leftover {}
+    set done 0
+    for {set i 0} {$i < [llength $todo]} {incr i} {
+	set do [lindex $todo $i]
+	if {![info exists commitrow($v,$do)] || $commitrow($v,$do) > $la} {
+	    lappend leftover $do
+	    continue
+	}
+	foreach np [lindex $parentlist $commitrow($v,$do)] {
+	    if {![info exists ancestor($np)]} {
+		set ancestor($np) 1
+		lappend todo $np
+		if {$np eq $a} {
+		    set done 1
+		}
+	    }
+	}
+	if {$done} {
+	    set anc_todo [concat $leftover [lrange $todo [expr {$i+1}] end]]
+	    return
+	}
+    }
+    set ancestor($a) 0
+    set anc_todo $leftover
+}
+
+proc askrelhighlight {row id} {
+    global descendent highlight_related iddrawn mainfont rhighlights
+    global selectedline ancestor
+
+    if {![info exists selectedline]} return
+    set isbold 0
+    if {$highlight_related eq "Descendent" ||
+	$highlight_related eq "Not descendent"} {
+	if {![info exists descendent($id)]} {
+	    is_descendent $id
+	}
+	if {$descendent($id) == ($highlight_related eq "Descendent")} {
+	    set isbold 1
+	}
+    } elseif {$highlight_related eq "Ancestor" ||
+	      $highlight_related eq "Not ancestor"} {
+	if {![info exists ancestor($id)]} {
+	    is_ancestor $id
+	}
+	if {$ancestor($id) == ($highlight_related eq "Ancestor")} {
+	    set isbold 1
+	}
+    }
+    if {[info exists iddrawn($id)]} {
+	if {$isbold && ![ishighlighted $row]} {
+	    bolden $row [concat $mainfont bold]
+	}
+    }
+    set rhighlights($row) $isbold
+}
+
 # Graph layout functions
 
 proc shortids {ids} {
@@ -2698,6 +2839,7 @@ proc drawcmitrow {row} {
     global commitinfo parentlist numcommits
     global filehighlight fhighlights findstring nhighlights
     global hlview vhighlights
+    global highlight_related rhighlights
 
     if {$row >= $numcommits} return
     foreach id [lindex $rowidlist $row] {
@@ -2727,6 +2869,9 @@ proc drawcmitrow {row} {
     if {$findstring ne {} && ![info exists nhighlights($row)]} {
 	askfindhighlight $row $id
     }
+    if {$highlight_related ne "None" && ![info exists rhighlights($row)]} {
+	askrelhighlight $row $id
+    }
     if {[info exists iddrawn($id)]} return
     set col [lsearch -exact [lindex $rowidlist $row] $id]
     if {$col < 0} {
@@ -2775,7 +2920,7 @@ proc drawvisible {} {
 
 proc clear_display {} {
     global iddrawn idrangedrawn
-    global vhighlights fhighlights nhighlights
+    global vhighlights fhighlights nhighlights rhighlights
 
     allcanvs delete all
     catch {unset iddrawn}
@@ -2783,6 +2928,7 @@ proc clear_display {} {
     catch {unset vhighlights}
     catch {unset fhighlights}
     catch {unset nhighlights}
+    catch {unset rhighlights}
 }
 
 proc findcrossings {id} {
@@ -3407,6 +3553,7 @@ proc selectline {l isnew} {
     $sha1entry insert 0 $id
     $sha1entry selection from 0
     $sha1entry selection to end
+    rhighlight_sel $id
 
     $ctext conf -state normal
     clear_ctext
@@ -3514,6 +3661,7 @@ proc unselectline {} {
     catch {unset selectedline}
     catch {unset currentid}
     allcanvs delete secsel
+    rhighlight_none
 }
 
 proc reselectline {} {