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>
diff --git a/lib/error.tcl b/lib/error.tcl
index 0fdd753..45800d5 100644
--- a/lib/error.tcl
+++ b/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 @@
 		-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 $cmd
 }
@@ -27,13 +31,13 @@
 		-type ok \
 		-title [append "$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 @@
 		-type yesno \
 		-title $title \
 		-message $msg]
-	if {[winfo ismapped .]} {
-		lappend cmd -parent .
+	if {[winfo ismapped [_error_parent]]} {
+		lappend cmd -parent [_error_parent]
 	}
 	eval $cmd
 }