builtin/apply: read_patch_file() return -1 instead of die()ing

To libify `git apply` functionality we have to signal errors to the
caller instead of die()ing. Let's do that by returning -1 instead of
die()ing in read_patch_file().

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

builtin/apply.c

@@ -335,10 +335,10 @@ static void say_patch_name(FILE *output, const char *fmt, struct patch *patch)
 
 #define SLOP (16)
 
-static void read_patch_file(struct strbuf *sb, int fd)
+static int read_patch_file(struct strbuf *sb, int fd)
 {
 	if (strbuf_read(sb, fd, 0) < 0)
-		die_errno("git apply: failed to read");
+		return error_errno("git apply: failed to read");
 
 	/*
 	 * Make sure that we have some slop in the buffer
@@ -347,6 +347,7 @@ static void read_patch_file(struct strbuf *sb, int fd)
 	 */
 	strbuf_grow(sb, SLOP);
 	memset(sb->buf + sb->len, 0, SLOP);
+	return 0;
 }
 
 static unsigned long linelen(const char *buffer, unsigned long size)
@@ -4425,7 +4426,8 @@ static int apply_patch(struct apply_state *state,
 	int res = 0;
 
 	state->patch_input_file = filename;
-	read_patch_file(&buf, fd);
+	if (read_patch_file(&buf, fd) < 0)
+		return -128;
 	offset = 0;
 	while (offset < buf.len) {
 		struct patch *patch;