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

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

To do that in a compatible manner with the rest of the error handling
in "builtin/apply.c", create_file() should just return what
add_conflicted_stages_file() and add_index_file() are returning
instead of calling exit().

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

builtin/apply.c

@@ -4269,7 +4269,7 @@ static int add_conflicted_stages_file(struct apply_state *state,
 	return 0;
 }
 
-static void create_file(struct apply_state *state, struct patch *patch)
+static int create_file(struct apply_state *state, struct patch *patch)
 {
 	char *path = patch->new_name;
 	unsigned mode = patch->new_mode;
@@ -4280,13 +4280,10 @@ static void create_file(struct apply_state *state, struct patch *patch)
 		mode = S_IFREG | 0644;
 	create_one_file(state, path, mode, buf, size);
 
-	if (patch->conflicted_threeway) {
-		if (add_conflicted_stages_file(state, patch))
-			exit(128);
-	} else {
-		if (add_index_file(state, path, mode, buf, size))
-			exit(128);
-	}
+	if (patch->conflicted_threeway)
+		return add_conflicted_stages_file(state, patch);
+	else
+		return add_index_file(state, path, mode, buf, size);
 }
 
 /* phase zero is to remove, phase one is to create */
@@ -4302,8 +4299,10 @@ static void write_out_one_result(struct apply_state *state,
 		return;
 	}
 	if (patch->is_new > 0 || patch->is_copy) {
-		if (phase == 1)
-			create_file(state, patch);
+		if (phase == 1) {
+			if (create_file(state, patch))
+				exit(128);
+		}
 		return;
 	}
 	/*
@@ -4314,8 +4313,10 @@ static void write_out_one_result(struct apply_state *state,
 		if (remove_file(state, patch, patch->is_rename))
 			exit(128);
 	}
-	if (phase == 1)
-		create_file(state, patch);
+	if (phase == 1) {
+		if (create_file(state, patch))
+			exit(128);
+	}
 }
 
 static int write_out_one_reject(struct apply_state *state, struct patch *patch)