git-gui: Create missing branch head on initial commit.

If we are making an initial commit our branch head did not exist when
we scanned for all heads during startup.  Consequently we won't have
it in our branch menu.  So force it to be put there after the ref was
created.

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

git-gui.sh

@@ -997,7 +997,7 @@ proc commit_writetree {curHEAD msg} {
 
 proc commit_committree {fd_wt curHEAD msg} {
 	global HEAD PARENT MERGE_HEAD commit_type
-	global single_commit
+	global single_commit all_heads current_branch
 	global ui_status_value ui_comm selected_commit_type
 	global file_states selected_paths rescan_active
 
@@ -1049,6 +1049,14 @@ proc commit_committree {fd_wt curHEAD msg} {
 		return
 	}
 
+	# -- Make sure our current branch exists.
+	#
+	if {$commit_type eq {initial}} {
+		lappend all_heads $current_branch
+		set all_heads [lsort -unique $all_heads]
+		populate_branch_menu
+	}
+
 	# -- Cleanup after ourselves.
 	#
 	catch {file delete [gitdir MERGE_HEAD]}