Re: [PATCH v2] test: set the realpath of CWD as TRASH_DIRECTORY

[Junio C Hamano <gitster@pobox.com>]

Michael Haggerty <mhagger@alum.mit.edu> writes:

> On 08/29/2012 08:06 AM, Junio C Hamano wrote:
>> Michael Haggerty <mhagger@alum.mit.edu> writes:
>
> It is in fact the whole approach that I object to.
> ...
>> What exactly is broken in CEILING?
>
> CEILING is used in setup_git_directory_gently_1() when trying to find
> the GIT_DIR appropriate for the current directory.  The entries in
> CEILING are compared textually to getcwd(), looking for the entry that
> is the longest proper prefix of PWD.  This is then used to limit a loop
> that is vaguely
>
>     while (!is_git_directory())
>             chdir("..");
>
> The problem, as I understand it, is that when the tests are run with
> root set to a path that includes a symlink, then test and
> TRASH_DIRECTORY are set to the textual value of "$root/trash
> directory.tXXXX", but then a little bit later test-lib.sh chdirs into
> the trash directory using "cd -P $test" (thereby resolving symlinks).
> So, taking my concrete example "--root=/dev/shm" where /dev/shm is a
> symlink to /run/shm, we have
>
>     test="/dev/shm/trash directory.tXXXX"
>     TRASH_DIRECTORY="$test"
>     ...
>     cd -P "$test"
>
> which results in PWD being "/run/shm/trash directory.tXXXX".

The components of CEILING should be adjusted to strip the symlink so
that it begins with "/run/shm/" before it is used; otherwise it
would not work.  As the current code does not do that at runtime (I
am describing the situation, not justifying), it won't match if
CEILING is built out of $TRASH_DIRECTORY.  In the above, setting of
$test and $TRASH is wrong; it does not match the realpath.

So "I somehow thought that Jiang's patch was to make sure any
variables that contain pathnames (and make sure future paths we
might grab out of $(pwd)) are realpath without symlinks early in the
test set-up," in my previous message was not correct.  The patch is
not doing that, and that is what breaks your setup.

My preference is to set things up in such a way that most of the
tests do not have to worry about these symlink aliases.  I know you
said you do not like the "whole approach", but I'd like to see our
tests run in a stable and reproducible testing environment.

We should have specific tests (on symlink enabled platforms) that
creates a directory and an alias to it via a symlink, goes into it
and checks the CEILING (and whatever else) behaviour.  We know that
the current code does not account for the alias introduced by
symlinks, and setup_git_directory_gently() may want to be patched to
fix _that_ specific test.