worktree: drop bogus and unnecessary path munging

The content of .git/worktrees/<id>/gitdir must be a path of the form
"/path/to/worktree/.git". Any other content would be indicative of a
corrupt "gitdir" file. To determine the path of the worktree itself one
merely strips the "/.git" suffix, and this is indeed how the worktree
path was determined from inception.

However, 5193490442 (worktree: add a function to get worktree details,
2015-10-08) extended the path manipulation in a mysterious way. If it is
unable to strip "/.git" from the path, then it instead reports the
current working directory as the linked worktree's path:

    if (!strbuf_strip_suffix(&worktree_path, "/.git")) {
        strbuf_reset(&worktree_path);
        strbuf_add_absolute_path(&worktree_path, ".");
        strbuf_strip_suffix(&worktree_path, "/.");
    }

This logic is clearly bogus; it can never be generally correct behavior.
It materialized out of thin air in 5193490442 with neither explanation
nor tests to illustrate a case in which it would be desirable.

It's possible that this logic was introduced to somehow deal with a
corrupt "gitdir" file, so that it returns _some_ sort of meaningful
value, but returning the current working directory is not helpful. In
fact, it is quite misleading (except in the one specific case when the
current directory is the worktree whose "gitdir" entry is corrupt).
Moreover, reporting the corrupt value to the user, rather than fibbing
about it and hiding it outright, is more helpful since it may aid in
diagnosing the problem.

Therefore, drop this bogus path munging and restore the logic to the
original behavior of merely stripping "/.git".

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

worktree.c

@@ -82,13 +82,8 @@ static struct worktree *get_linked_worktree(const char *id)
 	if (strbuf_read_file(&worktree_path, path.buf, 0) <= 0)
 		/* invalid gitdir file */
 		goto done;
-
 	strbuf_rtrim(&worktree_path);
-	if (!strbuf_strip_suffix(&worktree_path, "/.git")) {
-		strbuf_reset(&worktree_path);
-		strbuf_add_absolute_path(&worktree_path, ".");
-		strbuf_strip_suffix(&worktree_path, "/.");
-	}
+	strbuf_strip_suffix(&worktree_path, "/.git");
 
 	worktree = xcalloc(1, sizeof(*worktree));
 	worktree->path = strbuf_detach(&worktree_path, NULL);