bundle: add parse_bundle_header() helper function

Move most of the code from read_bundle_header() to parse_bundle_header()
that takes a file descriptor that is already opened for reading, and make
the former responsible only for opening the file and noticing errors.

As a logical consequence of this, is_bundle() helper function can be
implemented as a non-complaining variant of read_bundle_header() that
does not return an open file descriptor, and can be used to tighten
the check used to decide the use of bundle transport in transport_get()
function.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

bundle.c

@@ -40,19 +40,18 @@ static int strbuf_readline_fd(struct strbuf *sb, int fd)
 	return 0;
 }
 
-int read_bundle_header(const char *path, struct bundle_header *header)
+static int parse_bundle_header(int fd, struct bundle_header *header,
+			       const char *report_path)
 {
 	struct strbuf buf = STRBUF_INIT;
-	int fd = open(path, O_RDONLY);
 	int status = 0;
 
-	if (fd < 0)
-		return error("could not open '%s'", path);
-
 	/* The bundle header begins with the signature */
 	if (strbuf_readline_fd(&buf, fd) ||
 	    strcmp(buf.buf, bundle_signature)) {
-		error("'%s' does not look like a v2 bundle file", path);
+		if (report_path)
+			error("'%s' does not look like a v2 bundle file",
+			      report_path);
 		status = -1;
 		goto abort;
 	}
@@ -77,8 +76,9 @@ int read_bundle_header(const char *path, struct bundle_header *header)
 		if (get_sha1_hex(buf.buf, sha1) ||
 		    (40 <= buf.len && !isspace(buf.buf[40])) ||
 		    (!is_prereq && buf.len <= 40)) {
-			error("unrecognized header: %s%s (%d)",
-			      (is_prereq ? "-" : ""), buf.buf, (int)buf.len);
+			if (report_path)
+				error("unrecognized header: %s%s (%d)",
+				      (is_prereq ? "-" : ""), buf.buf, (int)buf.len);
 			status = -1;
 			break;
 		} else {
@@ -98,6 +98,29 @@ int read_bundle_header(const char *path, struct bundle_header *header)
 	return fd;
 }
 
+int read_bundle_header(const char *path, struct bundle_header *header)
+{
+	int fd = open(path, O_RDONLY);
+
+	if (fd < 0)
+		return error("could not open '%s'", path);
+	return parse_bundle_header(fd, header, path);
+}
+
+int is_bundle(const char *path, int quiet)
+{
+	struct bundle_header header;
+	int fd = open(path, O_RDONLY);
+
+	if (fd < 0)
+		return 0;
+	memset(&header, 0, sizeof(header));
+	fd = parse_bundle_header(fd, &header, quiet ? NULL : path);
+	if (fd >= 0)
+		close(fd);
+	return (fd >= 0);
+}
+
 static int list_refs(struct ref_list *r, int argc, const char **argv)
 {
 	int i;

bundle.h

@@ -14,6 +14,7 @@ struct bundle_header {
 	struct ref_list references;
 };
 
+int is_bundle(const char *path, int quiet);
 int read_bundle_header(const char *path, struct bundle_header *header);
 int create_bundle(struct bundle_header *header, const char *path,
 		int argc, const char **argv);

transport.c

@@ -913,7 +913,7 @@ struct transport *transport_get(struct remote *remote, const char *url)
 		ret->fetch = fetch_objs_via_rsync;
 		ret->push = rsync_transport_push;
 		ret->smart_options = NULL;
-	} else if (is_local(url) && is_file(url)) {
+	} else if (is_local(url) && is_file(url) && is_bundle(url, 1)) {
 		struct bundle_transport_data *data = xcalloc(1, sizeof(*data));
 		ret->data = data;
 		ret->get_refs_list = get_refs_from_bundle;