git-gui: Display the current branch name in browsers.

Rather than using HEAD for the current branch, use the actual name of
the current branch in the browser.  This way the user knows what a
browser is browsing if they open up different browsers while on different
branches.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>

git-gui.sh

@@ -2951,13 +2951,13 @@ proc reset_hard_wait {fd} {
 
 set next_browser_id 0
 
-proc new_browser {} {
+proc new_browser {commit} {
 	global next_browser_id cursor_ptr
 	global browser_commit browser_status browser_stack browser_path browser_busy
 
 	set w .browser[incr next_browser_id]
 	set w_list $w.list.l
-	set browser_commit($w_list) HEAD
+	set browser_commit($w_list) $commit
 	set browser_status($w_list) {Starting...}
 	set browser_stack($w_list) {}
 	set browser_path($w_list) $browser_commit($w_list):
@@ -4714,7 +4714,7 @@ menu .mbar.repository
 
 .mbar.repository add command \
 	-label {Browse Current Branch} \
-	-command new_browser \
+	-command {new_browser $current_branch} \
 	-font font_ui
 .mbar.repository add separator