worktree.c: find_worktree() search by path suffix

This allows the user to do something like "worktree lock foo" or
"worktree lock to/foo" instead of "worktree lock /long/path/to/foo" if
it's unambiguous.

With completion support it could be quite convenient. While this base
name search can be done in the same worktree iteration loop, the code is
split into a separate function for clarity.

Suggested-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-worktree.txt

@@ -129,6 +129,11 @@ OPTIONS
 <worktree>::
 	Working trees can be identified by path, either relative or
 	absolute.
++
+If the last path components in the working tree's path is unique among
+working trees, it can be used to identify worktrees. For example if
+you only have to working trees at "/abc/def/ghi" and "/abc/def/ggg",
+then "ghi" or "def/ghi" is enough to point to the former working tree.
 
 DETAILS
 -------

worktree.c

@@ -219,12 +219,41 @@ const char *get_worktree_git_dir(const struct worktree *wt)
 		return git_common_path("worktrees/%s", wt->id);
 }
 
+static struct worktree *find_worktree_by_suffix(struct worktree **list,
+						const char *suffix)
+{
+	struct worktree *found = NULL;
+	int nr_found = 0, suffixlen;
+
+	suffixlen = strlen(suffix);
+	if (!suffixlen)
+		return NULL;
+
+	for (; *list && nr_found < 2; list++) {
+		const char	*path	 = (*list)->path;
+		int		 pathlen = strlen(path);
+		int		 start	 = pathlen - suffixlen;
+
+		/* suffix must start at directory boundary */
+		if ((!start || (start > 0 && is_dir_sep(path[start - 1]))) &&
+		    !fspathcmp(suffix, path + start)) {
+			found = *list;
+			nr_found++;
+		}
+	}
+	return nr_found == 1 ? found : NULL;
+}
+
 struct worktree *find_worktree(struct worktree **list,
 			       const char *prefix,
 			       const char *arg)
 {
+	struct worktree *wt;
 	char *path;
 
+	if ((wt = find_worktree_by_suffix(list, arg)))
+		return wt;
+
 	arg = prefix_filename(prefix, strlen(prefix), arg);
 	path = xstrdup(real_path(arg));
 	for (; *list; list++)