Merge branch 'db/clone-in-c'

* db/clone-in-c:
  Add test for cloning with "--reference" repo being a subset of source repo
  Add a test for another combination of --reference
  Test that --reference actually suppresses fetching referenced objects
  clone: fall back to copying if hardlinking fails
  builtin-clone.c: Need to closedir() in copy_or_link_directory()
  builtin-clone: fix initial checkout
  Build in clone
  Provide API access to init_db()
  Add a function to set a non-default work tree
  Allow for having for_each_ref() list extra refs
  Have a constant extern refspec for "--tags"
  Add a library function to add an alternate to the alternates file
  Add a lockfile function to append to a file
  Mark the list of refs to fetch as const

Conflicts:

	cache.h
	t/t5700-clone-reference.sh

1 files changed, 28 insertions, 0 deletions

diff --git a/lockfile.c b/lockfile.c
index b0118d0592..cfc7335347 100644
--- a/lockfile.c
+++ b/lockfile.c
@@ -160,6 +160,34 @@ int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on
 	return fd;
 }
 
+int hold_lock_file_for_append(struct lock_file *lk, const char *path, int die_on_error)
+{
+	int fd, orig_fd;
+
+	fd = lock_file(lk, path);
+	if (fd < 0) {
+		if (die_on_error)
+			die("unable to create '%s.lock': %s", path, strerror(errno));
+		return fd;
+	}
+
+	orig_fd = open(path, O_RDONLY);
+	if (orig_fd < 0) {
+		if (errno != ENOENT) {
+			if (die_on_error)
+				die("cannot open '%s' for copying", path);
+			close(fd);
+			return error("cannot open '%s' for copying", path);
+		}
+	} else if (copy_fd(orig_fd, fd)) {
+		if (die_on_error)
+			exit(128);
+		close(fd);
+		return -1;
+	}
+	return fd;
+}
+
 int close_lock_file(struct lock_file *lk)
 {
 	int fd = lk->fd;