tree: allow skipping through single-child trees

If we have only a single element in a directory (for example in Java
package paths), display multiple directories in one go so that it is
possible to navigate directly to the first directory that contains
either files or multiple directories.

Signed-off-by: John Keeping <john@keeping.me.uk>

ui-tree.c

@@ -155,6 +155,72 @@ static void print_object(const unsigned char *sha1, char *path, const char *base
 		print_text_buffer(basename, buf, size);
 }
 
+struct single_tree_ctx {
+	struct strbuf *path;
+	unsigned char sha1[GIT_SHA1_RAWSZ];
+	char *name;
+	size_t count;
+};
+
+static int single_tree_cb(const unsigned char *sha1, struct strbuf *base,
+			  const char *pathname, unsigned mode, int stage,
+			  void *cbdata)
+{
+	struct single_tree_ctx *ctx = cbdata;
+
+	if (++ctx->count > 1)
+		return -1;
+
+	if (!S_ISDIR(mode)) {
+		ctx->count = 2;
+		return -1;
+	}
+
+	ctx->name = xstrdup(pathname);
+	hashcpy(ctx->sha1, sha1);
+	strbuf_addf(ctx->path, "/%s", pathname);
+	return 0;
+}
+
+static void write_tree_link(const unsigned char *sha1, char *name,
+			    char *rev, struct strbuf *fullpath)
+{
+	size_t initial_length = fullpath->len;
+	struct tree *tree;
+	struct single_tree_ctx tree_ctx = {
+		.path = fullpath,
+		.count = 1,
+	};
+	struct pathspec paths = {
+		.nr = 0
+	};
+
+	hashcpy(tree_ctx.sha1, sha1);
+
+	while (tree_ctx.count == 1) {
+		cgit_tree_link(name, NULL, "ls-dir", ctx.qry.head, rev,
+			       fullpath->buf);
+
+		tree = lookup_tree(tree_ctx.sha1);
+		if (!tree)
+			return;
+
+		free(tree_ctx.name);
+		tree_ctx.name = NULL;
+		tree_ctx.count = 0;
+
+		read_tree_recursive(tree, "", 0, 1, &paths, single_tree_cb,
+				    &tree_ctx);
+
+		if (tree_ctx.count != 1)
+			break;
+
+		html(" / ");
+		name = tree_ctx.name;
+	}
+
+	strbuf_setlen(fullpath, initial_length);
+}
 
 static int ls_item(const unsigned char *sha1, struct strbuf *base,
 		const char *pathname, unsigned mode, int stage, void *cbdata)
@@ -187,8 +253,8 @@ static int ls_item(const unsigned char *sha1, struct strbuf *base,
 	if (S_ISGITLINK(mode)) {
 		cgit_submodule_link("ls-mod", fullpath.buf, sha1_to_hex(sha1));
 	} else if (S_ISDIR(mode)) {
-		cgit_tree_link(name, NULL, "ls-dir", ctx.qry.head,
-			       walk_tree_ctx->curr_rev, fullpath.buf);
+		write_tree_link(sha1, name, walk_tree_ctx->curr_rev,
+				&fullpath);
 	} else {
 		char *ext = strrchr(name, '.');
 		strbuf_addstr(&class, "ls-blob");