completion: use git rev-parse to detect bare repos

Its check is more robust than a config check for core.bare

Trivially-Acked-by: Shawn O. Pearce <spearce@spearce.org>

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: Oblomov

contrib/completion/git-completion.bash

@@ -132,7 +132,7 @@ __git_ps1 ()
 		local c
 
 		if [ "true" = "$(git rev-parse --is-inside-git-dir 2>/dev/null)" ]; then
-			if [ "true" = "$(git config --bool core.bare 2>/dev/null)" ]; then
+			if [ "true" = "$(git rev-parse --is-bare-repository 2>/dev/null)" ]; then
 				c="BARE:"
 			else
 				b="GIT_DIR!"