Merge branch 'maint-1.6.1' into maint

* maint-1.6.1:
  grep: fix segfault when "git grep '('" is given
  Documentation: fix a grammatical error in api-builtin.txt
  builtin-merge: fix a typo in an error message

Documentation/technical/api-builtin.txt

@@ -37,7 +37,7 @@ where options is the bitwise-or of:
 
 	Make sure there is a work tree, i.e. the command cannot act
 	on bare repositories.
-	This makes only sense when `RUN_SETUP` is also set.
+	This only makes sense when `RUN_SETUP` is also set.
 
 . Add `builtin-foo.o` to `BUILTIN_OBJS` in `Makefile`.
 

builtin-merge.c

@@ -765,7 +765,7 @@ static int suggest_conflicts(void)
 
 	fp = fopen(git_path("MERGE_MSG"), "a");
 	if (!fp)
-		die("Could open %s for writing", git_path("MERGE_MSG"));
+		die("Could not open %s for writing", git_path("MERGE_MSG"));
 	fprintf(fp, "\nConflicts:\n");
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];

grep.c

@@ -70,6 +70,8 @@ static struct grep_expr *compile_pattern_atom(struct grep_pat **list)
 	struct grep_expr *x;
 
 	p = *list;
+	if (!p)
+		return NULL;
 	switch (p->token) {
 	case GREP_PATTERN: /* atom */
 	case GREP_PATTERN_HEAD:
@@ -82,8 +84,6 @@ static struct grep_expr *compile_pattern_atom(struct grep_pat **list)
 	case GREP_OPEN_PAREN:
 		*list = p->next;
 		x = compile_pattern_or(list);
-		if (!x)
-			return NULL;
 		if (!*list || (*list)->token != GREP_CLOSE_PAREN)
 			die("unmatched parenthesis");
 		*list = (*list)->next;
@@ -99,6 +99,8 @@ static struct grep_expr *compile_pattern_not(struct grep_pat **list)
 	struct grep_expr *x;
 
 	p = *list;
+	if (!p)
+		return NULL;
 	switch (p->token) {
 	case GREP_NOT:
 		if (!p->next)
@@ -386,6 +388,8 @@ static int match_expr_eval(struct grep_opt *o,
 {
 	int h = 0;
 
+	if (!x)
+		die("Not a valid grep expression");
 	switch (x->node) {
 	case GREP_NODE_ATOM:
 		h = match_one_pattern(o, x->u.atom, bol, eol, ctx);

t/t7002-grep.sh

@@ -26,6 +26,10 @@ test_expect_success setup '
 	git commit -m initial
 '
 
+test_expect_success 'grep should not segfault with a bad input' '
+	test_must_fail git grep "("
+'
+
 for H in HEAD ''
 do
 	case "$H" in