convert: move multiple file filter error handling to separate function

Refactoring the filter error handling is useful for the subsequent patch
'convert: add "status=delayed" to filter process protocol'.

In addition, replace the parentheses around the empty "if" block with a
single semicolon to adhere to the Git style guide.

Signed-off-by: Lars Schneider <larsxschneider@gmail.com>

convert.c

@@ -565,6 +565,29 @@ static int start_multi_file_filter_fn(struct subprocess_entry *subprocess)
 	return err;
 }
 
+static void handle_filter_error(const struct strbuf *filter_status,
+				struct cmd2process *entry,
+				const unsigned int wanted_capability) {
+	if (!strcmp(filter_status->buf, "error"))
+		; /* The filter signaled a problem with the file. */
+	else if (!strcmp(filter_status->buf, "abort") && wanted_capability) {
+		/*
+		 * The filter signaled a permanent problem. Don't try to filter
+		 * files with the same command for the lifetime of the current
+		 * Git process.
+		 */
+		 entry->supported_capabilities &= ~wanted_capability;
+	} else {
+		/*
+		 * Something went wrong with the protocol filter.
+		 * Force shutdown and restart if another blob requires filtering.
+		 */
+		error("external filter '%s' failed", entry->subprocess.cmd);
+		subprocess_stop(&subprocess_map, &entry->subprocess);
+		free(entry);
+	}
+}
+
 static int apply_multi_file_filter(const char *path, const char *src, size_t len,
 				   int fd, struct strbuf *dst, const char *cmd,
 				   const unsigned int wanted_capability)
@@ -656,28 +679,10 @@ static int apply_multi_file_filter(const char *path, const char *src, size_t len
 done:
 	sigchain_pop(SIGPIPE);
 
-	if (err) {
-		if (!strcmp(filter_status.buf, "error")) {
-			/* The filter signaled a problem with the file. */
-		} else if (!strcmp(filter_status.buf, "abort")) {
-			/*
-			 * The filter signaled a permanent problem. Don't try to filter
-			 * files with the same command for the lifetime of the current
-			 * Git process.
-			 */
-			 entry->supported_capabilities &= ~wanted_capability;
-		} else {
-			/*
-			 * Something went wrong with the protocol filter.
-			 * Force shutdown and restart if another blob requires filtering.
-			 */
-			error("external filter '%s' failed", cmd);
-			subprocess_stop(&subprocess_map, &entry->subprocess);
-			free(entry);
-		}
-	} else {
+	if (err)
+		handle_filter_error(&filter_status, entry, wanted_capability);
+	else
 		strbuf_swap(dst, &nbuf);
-	}
 	strbuf_release(&nbuf);
 	return !err;
 }