Re: [PATCH 0/8] Fix GIT_CEILING_DIRECTORIES that contain symlinks

> This series fixes longest_ancestor_length() so that it works even if
> prefix_list contains entries that involve symlinks.  The basic goal of
> the series is to call real_path() on each of the entries so that a
> textual comparison of the potential prefix to the front of path
> correctly decides whether the path is located inside of the entry.
> But along the way some other things had to be changed:
>
> * real_path() die()s if the path passed to it is invalid, whereas it
>   is allowed for GIT_CEILING_DIRECTORIES to contain invalid paths.  So
>   create a new function real_path_if_valid() that returns NULL for
>   invalid paths.
>
> * Changing longest_ancestor_length() to call real_path_if_valid()
>   would make the former very difficult to test (because the tests
>   would depend on the contents of the whole filesystem).  Therefore,
>   rewrite longest_ancestor_length() in terms of functions
>   string_list_split(), string_list_longest_prefix(), and
>   real_path_if_valid() which are tested individually.
>
> The net results of these changes are that:
>
> 1. t1504 used to have to canonicalize TRASH_DIRECTORY to make itself
>    work even if the --root directory contains symlinks.  This
>    canonicalization is no longer necessary (and has been removed).
>
> 2. t4035, which used to fail if the --root directory contained
>    symlinks, now works correctly in that situation.
>
> After this change, all tests pass if the --root directory does *not*
> contain symlinks, but t9903 still fails if the --root directory
> contains symlinks.  I haven't analyzed the cause of t9903's failure,
> but it does not appear to be related to the GIT_CEILING_DIRECTORIES
> feature.