Kill the blame back-end on window close.

Currently 'git-gui blame' does not kill its back-end
process, hoping that it will die anyway when the pipe
is closed. However, in some cases the process works
for a long time without producing any output. This
behavior results in a runaway CPU hog.
Signed-off-by: NAlexander Gavrilov <angavrilov@gmail.com>
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

git-gui.sh

@@ -497,6 +497,20 @@ proc githook_read {hook_name args} {
 	return {}
 }
 
+proc kill_file_process {fd} {
+	set process [pid $fd]
+
+	catch {
+		if {[is_Windows]} {
+			# Use a Cygwin-specific flag to allow killing
+			# native Windows processes
+			exec kill -f $process
+		} else {
+			exec kill $process
+		}
+	}
+}
+
 proc sq {value} {
 	regsub -all ' $value "'\\''" value
 	return "'$value'"

lib/blame.tcl

@@ -326,19 +326,27 @@ constructor new {i_commit i_path} {
 	bind $w.file_pane <Configure> \
 	"if {{$w.file_pane} eq {%W}} {[cb _resize %h]}"
 
+	wm protocol $top WM_DELETE_WINDOW "destroy $top"
+	bind $top <Destroy> [cb _kill]
+
 	_load $this {}
 }
 
+method _kill {} {
+	if {$current_fd ne {}} {
+		kill_file_process $current_fd
+		catch {close $current_fd}
+		set current_fd {}
+	}
+}
+
 method _load {jump} {
 	variable group_colors
 
 	_hide_tooltip $this
 
 	if {$total_lines != 0 || $current_fd ne {}} {
-		if {$current_fd ne {}} {
-			catch {close $current_fd}
-			set current_fd {}
-		}
+		_kill $this
 
 		foreach i $w_columns {
 			$i conf -state normal