Re: GIT_CEILING_DIRECTORY

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 9, 2016, 17:29 UTC
Message-ID: <xmqqshzzimpo.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <20160309110242.04d8d480@anarchist.wooz.org>

Barry Warsaw <barry@python.org> writes:

> I put my home directory under git (recently converted from bzr), but since I
> have some subdirectories under $HOME that are not under git (and some that
> are) I want to stop e.g. `git status` from traversing up into $HOME.

Let me understand the use case. You have $HOME/.git that governs everything under $HOME, but there are parts of $HOME/, such as $HOME/projects/*, that will never be controled by $HOME/.git?

Two obvious reactions are:

 - hopefully $HOME/.gitignore covers these non-git parts by having
   entries like '/projects/'; this should not affect the behaviour
   of CEILING though.

 - typing "git status" inside $HOME/projects/ does not make much
   sense in the first place.

I _think_ the "are we in a Git-managed working tree and if so, then where is the .git directory?" discovery works like this:

    - Are we sitting inside a subdirectory of one of the CEILING
      list elements?  For the purpose of this determination,
      directory 'foo' is not considered a subdirectory of 'foo'
      itself.  If we are, remember where the closest CEILING is.

    - Set the "directory we are checking" to the current directory.

    - Iterate:

      - Does the "directory we are checking" look like the root of a
        working tree managed by Git?  I.e. has ".git" directly in
        it, etc.  If so, we found the Git-managed working tree and
        its ".git".  Return.

      - Truncate one level from "directory we are checking",
        i.e. chdir(..);

      - Are we at a filesystem boundary (unless an environment tells
        us otherwise), or have we hit the closest CEILING we
        determined earlier?  We are not allowed to check if we are
        in a Git-managed working tree at higher level than this
        level.  Return.

      - Otherwise, keep checking.

So setting $HOME/projects as one of the elements in the CEILING list would not stop us going up if you are actually at $HOME/projects, but we would stop if you started from $HOME/projects/python.

This somehow sounds a bit inconsistent to me, but I say "a bit inconsistent" because "Why do we give different answer to 'is $HOME/projects/python governed by $HOME/.git?' depending on where we start the discovery process?" is a non-argument (i.e. that is not the question CEILING is answering).

I have a feeling that we must have done that for a reason. It may be interesting to see what breaks in t1504 if the above logic is updated to stop when you start at a CEILING (unlike the current code where it stops only when you start below a CEILING).