completion: make refs completion consistent for local and remote repos

For a local repository the __git_refs() completion helper function
lists refs under 'refs/(tags|heads|remotes)/', plus some special refs
like HEAD and ORIG_HEAD.  For a remote repository, however, it lists
all refs.

Fix this inconsistency by specifying refs filter patterns for 'git
ls-remote' to only list refs under 'refs/(tags|heads|remotes)/'.

For now this makes it impossible to complete refs outside of
'refs/(tags|heads|remotes)/' in a remote repository, but a followup
patch will resurrect that.

Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -616,13 +616,11 @@ __git_refs ()
 		fi
 		return
 	fi
-	for i in $(git ls-remote "$dir" 2>/dev/null); do
+	for i in $(git ls-remote "$dir" HEAD ORIG_HEAD 'refs/tags/*' 'refs/heads/*' 'refs/remotes/*' 2>/dev/null); do
 		case "$is_hash,$i" in
 		y,*) is_hash=n ;;
 		n,*^{}) is_hash=y ;;
-		n,refs/tags/*) is_hash=y; echo "${i#refs/tags/}" ;;
-		n,refs/heads/*) is_hash=y; echo "${i#refs/heads/}" ;;
-		n,refs/remotes/*) is_hash=y; echo "${i#refs/remotes/}" ;;
+		n,refs/*) is_hash=y; echo "${i#refs/*/}" ;;
 		n,*) is_hash=y; echo "$i" ;;
 		esac
 	done