gitk: Show nearby tags

This adds a feature to the diff display window where it will show
the tags that this commit follows (is a descendent of) and precedes
(is an ancestor of).  Specifically, it will show the tags for all
tagged descendents that are not a descendent of another tagged
descendent of this commit, and the tags for all tagged ancestors
that are not ancestors of another tagged ancestor of this commit.

To do this, gitk reads the complete commit graph using git rev-list
and performs a couple of traversals of the tree.  This is done in
the background, but since it can be time-consuming, there is an option
to turn it off in the `edit preferences' window.

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

gitk

@@ -743,7 +743,7 @@ proc click {w} {
 proc savestuff {w} {
     global canv canv2 canv3 ctext cflist mainfont textfont uifont
     global stuffsaved findmergefiles maxgraphpct
-    global maxwidth
+    global maxwidth showneartags
     global viewname viewfiles viewargs viewperm nextviewnum
     global cmitmode wrapcomment
 
@@ -759,6 +759,7 @@ proc savestuff {w} {
 	puts $f [list set maxwidth $maxwidth]
 	puts $f [list set cmitmode $cmitmode]
 	puts $f [list set wrapcomment $wrapcomment]
+	puts $f [list set showneartags $showneartags]
 	puts $f "set geometry(width) [winfo width .ctop]"
 	puts $f "set geometry(height) [winfo height .ctop]"
 	puts $f "set geometry(canv1) [expr {[winfo width $canv]-2}]"
@@ -3523,7 +3524,7 @@ proc commit_descriptor {p} {
     if {[llength $commitinfo($p)] > 1} {
 	set l [lindex $commitinfo($p) 0]
     }
-    return "$p ($l)"
+    return "$p ($l)\n"
 }
 
 # append some text to the ctext widget, and make any SHA1 ID
@@ -3533,7 +3534,6 @@ proc appendwithlinks {text tags} {
 
     set start [$ctext index "end - 1c"]
     $ctext insert end $text $tags
-    $ctext insert end "\n"
     set links [regexp -indices -all -inline {[0-9a-f]{40}} $text]
     foreach l $links {
 	set s [lindex $l 0]
@@ -3568,14 +3568,62 @@ proc viewnextline {dir} {
     allcanvs yview moveto [expr {$newtop * 1.0 / $ymax}]
 }
 
+# add a list of tag names at position pos
+proc appendrefs {pos l} {
+    global ctext commitrow linknum curview idtags
+
+    if {[catch {$ctext index $pos}]} return
+    set tags {}
+    foreach id $l {
+	foreach tag $idtags($id) {
+	    lappend tags [concat $tag $id]
+	}
+    }
+    set tags [lsort -index 1 $tags]
+    set sep {}
+    foreach tag $tags {
+	set name [lindex $tag 0]
+	set id [lindex $tag 1]
+	set lk link$linknum
+	incr linknum
+	$ctext insert $pos $sep
+	$ctext insert $pos $name $lk
+	$ctext tag conf $lk -foreground blue
+	if {[info exists commitrow($curview,$id)]} {
+	    $ctext tag bind $lk <1> \
+		[list selectline $commitrow($curview,$id) 1]
+	    $ctext tag conf $lk -underline 1
+	    $ctext tag bind $lk <Enter> { %W configure -cursor hand2 }
+	    $ctext tag bind $lk <Leave> { %W configure -cursor $curtextcursor }
+	}
+	set sep ", "
+    }
+}
+
+# called when we have finished computing the nearby tags
+proc dispneartags {} {
+    global selectedline currentid ctext anc_tags desc_tags showneartags
+
+    if {![info exists selectedline] || !$showneartags} return
+    set id $currentid
+    $ctext conf -state normal
+    if {[info exists anc_tags($id)]} {
+	appendrefs follows $anc_tags($id)
+    }
+    if {[info exists desc_tags($id)]} {
+	appendrefs precedes $desc_tags($id)
+    }
+    $ctext conf -state disabled
+}
+
 proc selectline {l isnew} {
     global canv canv2 canv3 ctext commitinfo selectedline
     global displayorder linehtag linentag linedtag
     global canvy0 linespc parentlist childlist
     global currentid sha1entry
     global commentend idtags linknum
     global mergemax numcommits pending_select
-    global cmitmode
+    global cmitmode desc_tags anc_tags showneartags allcommits
 
     catch {unset pending_select}
     $canv delete hover
@@ -3678,16 +3726,35 @@ proc selectline {l isnew} {
 	}
     } else {
 	foreach p $olds {
-	    append headers "Parent: [commit_descriptor $p]\n"
+	    append headers "Parent: [commit_descriptor $p]"
 	}
     }
 
     foreach c [lindex $childlist $l] {
-	append headers "Child:  [commit_descriptor $c]\n"
+	append headers "Child:  [commit_descriptor $c]"
     }
 
     # make anything that looks like a SHA1 ID be a clickable link
     appendwithlinks $headers {}
+    if {$showneartags} {
+	if {![info exists allcommits]} {
+	    getallcommits
+	}
+	$ctext insert end "Follows: "
+	$ctext mark set follows "end -1c"
+	$ctext mark gravity follows left
+	if {[info exists anc_tags($id)]} {
+	    appendrefs follows $anc_tags($id)
+	}
+	$ctext insert end "\nPrecedes: "
+	$ctext mark set precedes "end -1c"
+	$ctext mark gravity precedes left
+	if {[info exists desc_tags($id)]} {
+	    appendrefs precedes $desc_tags($id)
+	}
+	$ctext insert end "\n"
+    }
+    $ctext insert end "\n"
     appendwithlinks [lindex $info 5] {comment}
 
     $ctext tag delete Comments
@@ -4814,12 +4881,19 @@ proc domktag {} {
 
 proc redrawtags {id} {
     global canv linehtag commitrow idpos selectedline curview
+    global mainfont
 
     if {![info exists commitrow($curview,$id)]} return
     drawcmitrow $commitrow($curview,$id)
     $canv delete tag.$id
     set xt [eval drawtags $id $idpos($id)]
     $canv coords $linehtag($commitrow($curview,$id)) $xt [lindex $idpos($id) 2]
+    set text [$canv itemcget $linehtag($commitrow($curview,$id)) -text]
+    set xr [expr {$xt + [font measure $mainfont $text]}]
+    if {$xr > $canvxmax} {
+	set canvxmax $xr
+	setcanvscroll
+    }
     if {[info exists selectedline]
 	&& $selectedline == $commitrow($curview,$id)} {
 	selectline $selectedline 0
@@ -4893,22 +4967,164 @@ proc wrcomcan {} {
     unset wrcomtop
 }
 
-proc listrefs {id} {
-    global idtags idheads idotherrefs
+# Stuff for finding nearby tags
+proc getallcommits {} {
+    global allcstart allcommits
 
-    set x {}
-    if {[info exists idtags($id)]} {
-	set x $idtags($id)
+    set fd [open [concat | git rev-list --all --topo-order --parents] r]
+    fconfigure $fd -blocking 0
+    set allcommits "reading"
+    nowbusy allcommits
+    restartgetall $fd
+}
+
+proc restartgetall {fd} {
+    global allcstart
+
+    fileevent $fd readable [list getallclines $fd]
+    set allcstart [clock clicks -milliseconds]
+}
+
+proc combine_dtags {l1 l2} {
+    global tagisdesc notfirstd
+
+    set res [lsort -unique [concat $l1 $l2]]
+    for {set i 0} {$i < [llength $res]} {incr i} {
+	set x [lindex $res $i]
+	for {set j [expr {$i+1}]} {$j < [llength $res]} {} {
+	    set y [lindex $res $j]
+	    if {[info exists tagisdesc($x,$y)]} {
+		if {$tagisdesc($x,$y) > 0} {
+		    # x is a descendent of y, exclude x
+		    set res [lreplace $res $i $i]
+		    incr i -1
+		    break
+		} else {
+		    # y is a descendent of x, exclude y
+		    set res [lreplace $res $j $j]
+		}
+	    } else {
+		# no relation, keep going
+		incr j
+	    }
+	}
     }
-    set y {}
-    if {[info exists idheads($id)]} {
-	set y $idheads($id)
+    return $res
+}
+
+proc combine_atags {l1 l2} {
+    global tagisdesc
+
+    set res [lsort -unique [concat $l1 $l2]]
+    for {set i 0} {$i < [llength $res]} {incr i} {
+	set x [lindex $res $i]
+	for {set j [expr {$i+1}]} {$j < [llength $res]} {} {
+	    set y [lindex $res $j]
+	    if {[info exists tagisdesc($x,$y)]} {
+		if {$tagisdesc($x,$y) < 0} {
+		    # x is an ancestor of y, exclude x
+		    set res [lreplace $res $i $i]
+		    incr i -1
+		    break
+		} else {
+		    # y is an ancestor of x, exclude y
+		    set res [lreplace $res $j $j]
+		}
+	    } else {
+		# no relation, keep going
+		incr j
+	    }
+	}
     }
-    set z {}
-    if {[info exists idotherrefs($id)]} {
-	set z $idotherrefs($id)
+    return $res
+}
+
+proc getallclines {fd} {
+    global allparents allchildren allcommits allcstart
+    global desc_tags anc_tags idtags alldtags tagisdesc allids
+
+    while {[gets $fd line] >= 0} {
+	set id [lindex $line 0]
+	lappend allids $id
+	set olds [lrange $line 1 end]
+	set allparents($id) $olds
+	if {![info exists allchildren($id)]} {
+	    set allchildren($id) {}
+	}
+	foreach p $olds {
+	    lappend allchildren($p) $id
+	}
+	# compute nearest tagged descendents as we go
+	set dtags {}
+	foreach child $allchildren($id) {
+	    if {[info exists idtags($child)]} {
+		set ctags [list $child]
+	    } else {
+		set ctags $desc_tags($child)
+	    }
+	    if {$dtags eq {}} {
+		set dtags $ctags
+	    } elseif {$ctags ne $dtags} {
+		set dtags [combine_dtags $dtags $ctags]
+	    }
+	}
+	set desc_tags($id) $dtags
+	if {[info exists idtags($id)]} {
+	    set adt $dtags
+	    foreach tag $dtags {
+		set adt [concat $adt $alldtags($tag)]
+	    }
+	    set adt [lsort -unique $adt]
+	    set alldtags($id) $adt
+	    foreach tag $adt {
+		set tagisdesc($id,$tag) -1
+		set tagisdesc($tag,$id) 1
+	    }
+	}
+	if {[clock clicks -milliseconds] - $allcstart >= 50} {
+	    fileevent $fd readable {}
+	    after idle restartgetall $fd
+	    return
+	}
+    }
+    if {[eof $fd]} {
+	after idle restartatags [llength $allids]
+	if {[catch {close $fd} err]} {
+	    error_popup "Error reading full commit graph: $err.\n\
+			 Results may be incomplete."
+	}
+    }
+}
+
+# walk backward through the tree and compute nearest tagged ancestors
+proc restartatags {i} {
+    global allids allparents idtags anc_tags t0
+
+    set t0 [clock clicks -milliseconds]
+    while {[incr i -1] >= 0} {
+	set id [lindex $allids $i]
+	set atags {}
+	foreach p $allparents($id) {
+	    if {[info exists idtags($p)]} {
+		set ptags [list $p]
+	    } else {
+		set ptags $anc_tags($p)
+	    }
+	    if {$atags eq {}} {
+		set atags $ptags
+	    } elseif {$ptags ne $atags} {
+		set atags [combine_atags $atags $ptags]
+	    }
+	}
+	set anc_tags($id) $atags
+	if {[clock clicks -milliseconds] - $t0 >= 50} {
+	    after idle restartatags $i
+	    return
+	}
     }
-    return [list $x $y $z]
+    set allcommits "done"
+    notbusy allcommits
+    dispneartags
 }
 
 proc rereadrefs {} {
@@ -4959,15 +5175,15 @@ proc doquit {} {
 
 proc doprefs {} {
     global maxwidth maxgraphpct diffopts
-    global oldprefs prefstop
+    global oldprefs prefstop showneartags
 
     set top .gitkprefs
     set prefstop $top
     if {[winfo exists $top]} {
 	raise $top
 	return
     }
-    foreach v {maxwidth maxgraphpct diffopts} {
+    foreach v {maxwidth maxgraphpct diffopts showneartags} {
 	set oldprefs($v) [set $v]
     }
     toplevel $top
@@ -4989,6 +5205,11 @@ proc doprefs {} {
 	-font optionfont
     entry $top.diffopt -width 20 -textvariable diffopts
     grid x $top.diffoptl $top.diffopt -sticky w
+    frame $top.ntag
+    label $top.ntag.l -text "Display nearby tags" -font optionfont
+    checkbutton $top.ntag.b -variable showneartags
+    pack $top.ntag.b $top.ntag.l -side left
+    grid x $top.ntag -sticky w
     frame $top.buts
     button $top.buts.ok -text "OK" -command prefsok
     button $top.buts.can -text "Cancel" -command prefscan
@@ -5000,9 +5221,9 @@ proc doprefs {} {
 
 proc prefscan {} {
     global maxwidth maxgraphpct diffopts
-    global oldprefs prefstop
+    global oldprefs prefstop showneartags
 
-    foreach v {maxwidth maxgraphpct diffopts} {
+    foreach v {maxwidth maxgraphpct diffopts showneartags} {
 	set $v $oldprefs($v)
     }
     catch {destroy $prefstop}
@@ -5011,13 +5232,15 @@ proc prefscan {} {
 
 proc prefsok {} {
     global maxwidth maxgraphpct
-    global oldprefs prefstop
+    global oldprefs prefstop showneartags
 
     catch {destroy $prefstop}
     unset prefstop
     if {$maxwidth != $oldprefs(maxwidth)
 	|| $maxgraphpct != $oldprefs(maxgraphpct)} {
 	redisplay
+    } elseif {$showneartags != $oldprefs(showneartags)} {
+	reselectline
     }
 }
 
@@ -5328,6 +5551,7 @@ set downarrowlen 7
 set mingaplen 30
 set cmitmode "patch"
 set wrapcomment "none"
+set showneartags 1
 
 set colors {green red blue magenta darkgrey brown orange}