git-gui: Ensure error dialogs always appear over all other windows

If we are opening an error dialog we want it to appear above all of
the other windows, even those that we may have opened with a grab
to make the window modal.  Failure to do so may allow an error
dialog to open up (and grab focus!) under an existing toplevel,
making the user think git-gui has frozen up and is unresponsive,
as they cannot get to the dialog.

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

lib/error.tcl

@@ -1,6 +1,10 @@
 # git-gui branch (create/delete) support
 # Copyright (C) 2006, 2007 Shawn Pearce
 
+proc _error_parent {} {
+	return [grab current .]
+}
+
 proc error_popup {msg} {
 	set title [appname]
 	if {[reponame] ne {}} {
@@ -11,8 +15,8 @@ proc error_popup {msg} {
 		-type ok \
 		-title [append "$title: " [mc "error"]] \
 		-message $msg]
-	if {[winfo ismapped .]} {
-		lappend cmd -parent .
+	if {[winfo ismapped [_error_parent]]} {
+		lappend cmd -parent [_error_parent]
 	}
 	eval $cmd
 }
@@ -27,13 +31,13 @@ proc warn_popup {msg} {
 		-type ok \
 		-title [append "$title: " [mc "warning"]] \
 		-message $msg]
-	if {[winfo ismapped .]} {
-		lappend cmd -parent .
+	if {[winfo ismapped [_error_parent]]} {
+		lappend cmd -parent [_error_parent]
 	}
 	eval $cmd
 }
 
-proc info_popup {msg {parent .}} {
+proc info_popup {msg} {
 	set title [appname]
 	if {[reponame] ne {}} {
 		append title " ([reponame])"
@@ -56,8 +60,8 @@ proc ask_popup {msg} {
 		-type yesno \
 		-title $title \
 		-message $msg]
-	if {[winfo ismapped .]} {
-		lappend cmd -parent .
+	if {[winfo ismapped [_error_parent]]} {
+		lappend cmd -parent [_error_parent]
 	}
 	eval $cmd
 }