Merge branch 'maint-1.6.0' into maint-1.6.1

* maint-1.6.0:
  Fix bash completion in path with spaces
  bash completion: only show 'log --merge' if merging
  git-tag(1): add hint about commit messages
  Documentation: update graph api example.

contrib/completion/git-completion.bash

@@ -935,6 +935,11 @@ _git_log ()
 	__git_has_doubledash && return
 
 	local cur="${COMP_WORDS[COMP_CWORD]}"
+	local g="$(git rev-parse --git-dir 2>/dev/null)"
+	local merge=""
+	if [ -f "$g/MERGE_HEAD" ]; then
+		merge="--merge"
+	fi
 	case "$cur" in
 	--pretty=*)
 		__gitcomp "
@@ -966,7 +971,7 @@ _git_log ()
 			--decorate --diff-filter=
 			--color-words --walk-reflogs
 			--parents --children --full-history
-			--merge
+			$merge
 			"
 		return
 		;;
@@ -1751,7 +1756,7 @@ _gitk ()
 	local cur="${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