Fix bash completion in path with spaces

Signed-off-by: Daniel Cheng (aka SDiZ) <j16sdiz+freenet@gmail.com>
Trivially-acked-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -939,7 +939,7 @@ _git_log ()
 	local cur="${COMP_WORDS[COMP_CWORD]}"
 	local g="$(git rev-parse --git-dir 2>/dev/null)"
 	local merge=""
-	if [ -f $g/MERGE_HEAD ]; then
+	if [ -f "$g/MERGE_HEAD" ]; then
 		merge="--merge"
 	fi
 	case "$cur" in
@@ -1681,7 +1681,7 @@ _gitk ()
 	local cur="${COMP_WORDS[COMP_CWORD]}"
 	local g="$(git rev-parse --git-dir 2>/dev/null)"
 	local merge=""
-	if [ -f $g/MERGE_HEAD ]; then
+	if [ -f "$g/MERGE_HEAD" ]; then
 		merge="--merge"
 	fi
 	case "$cur" in