Merge branch 'jc/gitlink' into next

* jc/gitlink:
  write-tree: --prefix=<path>
  read-tree: --prefix=<path>/ option.

cache-tree.c

@@ -529,3 +529,29 @@ struct cache_tree *cache_tree_read(const char *buffer, unsigned long size)
 		return NULL; /* not the whole tree */
 	return read_one(&buffer, &size);
 }
+
+struct cache_tree *cache_tree_find(struct cache_tree *it, const char *path)
+{
+	while (*path) {
+		const char *slash;
+		struct cache_tree_sub *sub;
+
+		slash = strchr(path, '/');
+		if (!slash)
+			slash = path + strlen(path);
+		/* between path and slash is the name of the
+		 * subtree to look for.
+		 */
+		sub = find_subtree(it, path, slash - path, 0);
+		if (!sub)
+			return NULL;
+		it = sub->cache_tree;
+		if (slash)
+			while (*slash && *slash == '/')
+				slash++;
+		if (!slash || !*slash)
+			return it; /* prefix ended with slashes */
+		path = slash;
+	}
+	return it;
+}