builtin/apply: make find_header() return -128 instead of die()ing

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, let's make find_header() return -128 instead of
calling die().

We could make it return -1, unfortunately find_header() already
returns -1 when no header is found.

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

builtin/apply.c

@@ -1419,6 +1419,14 @@ static int parse_fragment_header(const char *line, int len, struct fragment *fra
 	return offset;
 }
 
+/*
+ * Find file diff header
+ *
+ * Returns:
+ *  -1 if no header was found
+ *  -128 in case of error
+ *   the size of the header in bytes (called "offset") otherwise
+ */
 static int find_header(struct apply_state *state,
 		       const char *line,
 		       unsigned long size,
@@ -1452,8 +1460,9 @@ static int find_header(struct apply_state *state,
 			struct fragment dummy;
 			if (parse_fragment_header(line, len, &dummy) < 0)
 				continue;
-			die(_("patch fragment without header at line %d: %.*s"),
+			error(_("patch fragment without header at line %d: %.*s"),
 				     state->linenr, (int)len-1, line);
+			return -128;
 		}
 
 		if (size < len + 6)
@@ -1468,19 +1477,23 @@ static int find_header(struct apply_state *state,
 			if (git_hdr_len <= len)
 				continue;
 			if (!patch->old_name && !patch->new_name) {
-				if (!patch->def_name)
-					die(Q_("git diff header lacks filename information when removing "
+				if (!patch->def_name) {
+					error(Q_("git diff header lacks filename information when removing "
 							"%d leading pathname component (line %d)",
 							"git diff header lacks filename information when removing "
 							"%d leading pathname components (line %d)",
 							state->p_value),
 						     state->p_value, state->linenr);
+					return -128;
+				}
 				patch->old_name = xstrdup(patch->def_name);
 				patch->new_name = xstrdup(patch->def_name);
 			}
-			if (!patch->is_delete && !patch->new_name)
-				die("git diff header lacks filename information "
+			if (!patch->is_delete && !patch->new_name) {
+				error("git diff header lacks filename information "
 					     "(line %d)", state->linenr);
+				return -128;
+			}
 			patch->is_toplevel_relative = 1;
 			*hdrsize = git_hdr_len;
 			return offset;
@@ -1996,6 +2009,9 @@ static int parse_chunk(struct apply_state *state, char *buffer, unsigned long si
 	int hdrsize, patchsize;
 	int offset = find_header(state, buffer, size, &hdrsize, patch);
 
+	if (offset == -128)
+		exit(128);
+
 	if (offset < 0)
 		return offset;
 

t/t4254-am-corrupt.sh

@@ -29,7 +29,7 @@ test_expect_success 'try to apply corrupted patch' '
 '
 
 test_expect_success 'compare diagnostic; ensure file is still here' '
-	echo "fatal: git diff header lacks filename information (line 4)" >expected &&
+	echo "error: git diff header lacks filename information (line 4)" >expected &&
 	test_path_is_file f &&
 	test_cmp expected actual
 '