git-gui: Include commit id/subject in merge choices

When merging branches using our local merge feature it can be
handy to know the first few digits of the commit the ref points
at as well as the short description of the branch name.

Unfortunately I'm unable to use three listboxes in a row, as Tcl
freaks out and refuses to let me have a selection in more than
one of them at any given point in time.  So instead we use a
fixed width font in the existing listbox and organize the data
into three columns.  Not nearly as nice looking, but users can
continue to use the listbox's features.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

lib/merge.tcl

@@ -63,28 +63,28 @@ You should complete the current commit before starting a merge.  Doing so will h
 	return 1
 }
 
-proc _visualize {w} {
+proc _refs {w list} {
-	set revs {}
+	set r {}
 	foreach i [$w.source.l curselection] {
-		lappend revs [$w.source.l get $i]
+		lappend r [lindex [lindex $list $i] 0]
 	}
+	return $r
+}
+
+proc _visualize {w list} {
+	set revs [_refs $w $list]
 	if {$revs eq {}} return
 	lappend revs --not HEAD
 	do_gitk $revs
 }
 
-proc _start {w} {
+proc _start {w list} {
 	global HEAD ui_status_value current_branch
 
 	set cmd [list git merge]
-	set names {}
+	set names [_refs $w $list]
-	set revcnt 0
+	set revcnt [llength $names]
-	foreach i [$w.source.l curselection] {
+	append cmd { } $names
-		set b [$w.source.l get $i]
-		lappend cmd $b
-		lappend names $b
-		incr revcnt
-	}
 
 	if {$revcnt == 0} {
 		return
@@ -163,38 +163,6 @@ proc dialog {} {
 
 	if {![_can_merge]} return
 
-	set w .merge_setup
-	toplevel $w
-	wm geometry $w "+[winfo rootx .]+[winfo rooty .]"
-
-	label $w.header \
-		-text "Merge Into $current_branch" \
-		-font font_uibold
-	pack $w.header -side top -fill x
-
-	frame $w.buttons
-	button $w.buttons.visualize -text Visualize \
-		-command [namespace code [list _visualize $w]]
-	pack $w.buttons.visualize -side left
-	button $w.buttons.create -text Merge \
-		-command [namespace code [list _start $w]]
-	pack $w.buttons.create -side right
-	button $w.buttons.cancel -text {Cancel} \
-		-command [list destroy $w]
-	pack $w.buttons.cancel -side right -padx 5
-	pack $w.buttons -side bottom -fill x -pady 10 -padx 10
-
-	labelframe $w.source -text {Source Branches}
-	listbox $w.source.l \
-		-height 10 \
-		-width 70 \
-		-selectmode extended \
-		-yscrollcommand [list $w.source.sby set]
-	scrollbar $w.source.sby -command [list $w.source.l yview]
-	pack $w.source.sby -side right -fill y
-	pack $w.source.l -side left -fill both -expand 1
-	pack $w.source -fill both -expand 1 -pady 5 -padx 5
-
 	set fmt {list %(objectname) %(*objectname) %(refname) %(subject)}
 	set cmd [list git for-each-ref --tcl --format=$fmt]
 	lappend cmd refs/heads
@@ -219,16 +187,57 @@ proc dialog {} {
 	while {[gets $fr_fd line] > 0} {
 		if {[catch {set ref $sha1($line)}]} continue
 		foreach n $ref {
-			lappend to_show $n
+			lappend to_show [list $n $line]
 		}
 	}
 	close $fr_fd
+	set to_show [lsort -unique $to_show]
 
-	foreach ref [lsort -unique $to_show] {
+	set w .merge_setup
-		$w.source.l insert end $ref
+	toplevel $w
+	wm geometry $w "+[winfo rootx .]+[winfo rooty .]"
+
+	label $w.header \
+		-text "Merge Into $current_branch" \
+		-font font_uibold
+	pack $w.header -side top -fill x
+
+	frame $w.buttons
+	button $w.buttons.visualize -text Visualize \
+		-command [namespace code [list _visualize $w $to_show]]
+	pack $w.buttons.visualize -side left
+	button $w.buttons.create -text Merge \
+		-command [namespace code [list _start $w $to_show]]
+	pack $w.buttons.create -side right
+	button $w.buttons.cancel -text {Cancel} \
+		-command [list destroy $w]
+	pack $w.buttons.cancel -side right -padx 5
+	pack $w.buttons -side bottom -fill x -pady 10 -padx 10
+
+	labelframe $w.source -text {Source Branches}
+	listbox $w.source.l \
+		-height 10 \
+		-width 70 \
+		-font font_diff \
+		-selectmode extended \
+		-yscrollcommand [list $w.source.sby set]
+	scrollbar $w.source.sby -command [list $w.source.l yview]
+	pack $w.source.sby -side right -fill y
+	pack $w.source.l -side left -fill both -expand 1
+	pack $w.source -fill both -expand 1 -pady 5 -padx 5
+
+	foreach ref $to_show {
+		set n [lindex $ref 0]
+		if {[string length $n] > 20} {
+			set n "[string range $n 0 16]..."
+		}
+		$w.source.l insert end [format {%s %-20s %s} \
+			[string range [lindex $ref 1] 0 5] \
+			$n \
+			$subj([lindex $ref 0])]
 	}
 
-	bind $w <Visibility> "grab $w"
+	bind $w <Visibility> "grab $w; focus $w.source.l"
 	bind $w <Key-Escape> "unlock_index;destroy $w"
 	bind $w <Destroy> unlock_index
 	wm title $w "[appname] ([reponame]): Merge"