git-gui: Efficiently update the UI after committing.

When we commit we know that whatever was in the index went as part
of the commit.  Since we generally assume that the user does not
update the index except through our user interface we can be reasonably
certain that any file which was marked as A/M/D in the index will have
had that A/M/D state changed to an _ (not different) by the commit.

We can use this knowledge to update the user interface post commit
by simply updating the index part of the file state of all files whose
index state was A/M/D to _ and then removing any file memory any which
wound up with a final state of __ (not different anywhere).  Finally we
redraw the file lists and update the diff view.

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

git-gui

@@ -150,7 +150,7 @@ proc repository_state {hdvar ctvar} {
 proc update_status {{final Ready.}} {
 	global HEAD PARENT commit_type
 	global ui_index ui_other ui_status_value ui_comm
-	global status_active file_states file_lists
+	global status_active file_states
 	global cfg_trust_mtime
 
 	if {$status_active || ![lock_index read]} return
@@ -166,12 +166,6 @@ proc update_status {{final Ready.}} {
 	}
 
 	array unset file_states
-	array unset file_lists
-	foreach w [list $ui_index $ui_other] {
-		$w conf -state normal
-		$w delete 0.0 end
-		$w conf -state disabled
-	}
 
 	if {![$ui_comm edit modified]
 		|| [string trim [$ui_comm get 0.0 end]] == {}} {
@@ -319,25 +313,18 @@ proc read_ls_others {fd final} {
 }
 
 proc status_eof {fd buf final} {
-	global status_active $buf
-	global ui_fname_value ui_status_value file_states
+	global status_active ui_status_value
+	upvar $buf to_clear
 
 	if {[eof $fd]} {
-		set $buf {}
+		set to_clear {}
 		close $fd
 
 		if {[incr status_active -1] == 0} {
-			unlock_index
-
 			display_all_files
+			unlock_index
+			reshow_diff
 			set ui_status_value $final
-
-			if {$ui_fname_value != {} && [array names file_states \
-				-exact $ui_fname_value] != {}}  {
-				show_diff $ui_fname_value
-			} else {
-				clear_diff
-			}
 		}
 	}
 }
@@ -360,6 +347,17 @@ proc clear_diff {} {
 	$ui_other tag remove in_diff 0.0 end
 }
 
+proc reshow_diff {} {
+	global ui_fname_value ui_status_value file_states
+
+	if {$ui_fname_value != {} && [array names file_states \
+		-exact $ui_fname_value] != {}}  {
+		show_diff $ui_fname_value
+	} else {
+		clear_diff
+	}
+}
+
 proc show_diff {path {w {}} {lno {}}} {
 	global file_states file_lists
 	global PARENT diff_3way diff_active
@@ -562,11 +560,11 @@ before committing.
 	foreach path [array names file_states] {
 		set s $file_states($path)
 		switch -glob -- [lindex $s 0] {
-		_* {continue}
-		A* -
-		D* -
-		M* {set files_ready 1; break}
-		U* {
+		_? {continue}
+		A? -
+		D? -
+		M? {set files_ready 1; break}
+		U? {
 			error_popup "Unmerged files cannot be committed.
 
 File [escape_path $path] has merge conflicts.
@@ -635,8 +633,9 @@ A good commit message has the following format:
 }
 
 proc commit_stage2 {fd_wt curHEAD msg} {
-	global single_commit gitdir PARENT commit_type
+	global single_commit gitdir HEAD PARENT commit_type
 	global commit_active ui_status_value ui_comm
+	global file_states
 
 	gets $fd_wt tree_id
 	close $fd_wt
@@ -663,7 +662,7 @@ proc commit_stage2 {fd_wt curHEAD msg} {
 				}
 				close $fd_mh
 			} err]} {
-			error_popup "Loading MERGE_HEADs failed:\n$err"
+			error_popup "Loading MERGE_HEAD failed:\n$err"
 			set commit_active 0
 			set ui_status_value {Commit failed.}
 			unlock_index
@@ -723,12 +722,34 @@ proc commit_stage2 {fd_wt curHEAD msg} {
 
 	if {$single_commit} do_quit
 
-	set commit_type {}
+	# -- Update status without invoking any git commands.
+	#
 	set commit_active 0
+	set commit_type normal
 	set HEAD $cmt_id
 	set PARENT $cmt_id
+
+	foreach path [array names file_states] {
+		set s $file_states($path)
+		set m [lindex $s 0]
+		switch -glob -- $m {
+		A? -
+		M? -
+		D? {set m _[string index $m 1]}
+		}
+
+		if {$m == {__}} {
+			unset file_states($path)
+		} else {
+			lset file_states($path) 0 $m
+		}
+	}
+
+	display_all_files
 	unlock_index
-	update_status "Changes committed as [string range $cmt_id 0 7]."
+	reshow_diff
+	set ui_status_value \
+		"Changes committed as [string range $cmt_id 0 7]."
 }
 
 ######################################################################
@@ -925,6 +946,10 @@ proc display_all_files {} {
 	$ui_index conf -state normal
 	$ui_other conf -state normal
 
+	$ui_index delete 0.0 end
+	$ui_other delete 0.0 end
+
+	array unset file_lists
 	foreach path [lsort [array names file_states]] {
 		set s $file_states($path)
 		set m [lindex $s 0]
@@ -1506,10 +1531,12 @@ proc click {w x y shift wx wy} {
 }
 
 proc unclick {w x y} {
+	global file_lists
+
 	set pos [split [$w index @$x,$y] .]
 	set lno [lindex $pos 0]
 	set col [lindex $pos 1]
-	set path [$w get $lno.1 $lno.end]
+	set path [lindex $file_lists($w) [expr $lno - 1]]
 	if {$path == {}} return
 
 	if {$col == 0} {