builtin/apply: make parse_traditional_patch() return -1 on error

To libify `git apply` functionality we have to signal errors to the
caller instead of die()ing.

To do that in a compatible manner with the rest of the error handling
in "builtin/apply.c", parse_traditional_patch() should return -1
instead of calling die().

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/apply.c

@@ -755,10 +755,10 @@ static int has_epoch_timestamp(const char *nameline)
  * files, we can happily check the index for a match, but for creating a
  * new file we should try to match whatever "patch" does. I have no idea.
  */
-static void parse_traditional_patch(struct apply_state *state,
-				    const char *first,
-				    const char *second,
-				    struct patch *patch)
+static int parse_traditional_patch(struct apply_state *state,
+				   const char *first,
+				   const char *second,
+				   struct patch *patch)
 {
 	char *name;
 
@@ -803,7 +803,9 @@ static void parse_traditional_patch(struct apply_state *state,
 		}
 	}
 	if (!name)
-		die(_("unable to find filename in patch at line %d"), state->linenr);
+		return error(_("unable to find filename in patch at line %d"), state->linenr);
+
+	return 0;
 }
 
 static int gitdiff_hdrend(struct apply_state *state,
@@ -1467,7 +1469,8 @@ static int find_header(struct apply_state *state,
 			continue;
 
 		/* Ok, we'll consider it a patch */
-		parse_traditional_patch(state, line, line+len, patch);
+		if (parse_traditional_patch(state, line, line+len, patch))
+			return -128;
 		*hdrsize = len + nextlen;
 		state->linenr += 2;
 		return offset;