Re: [RFC PATCH] rev-parse: add --show-superproject-working-tree

From: Junio C Hamano <gitster@pobox.com>
Date: Mar 7, 2017, 07:16 UTC
Message-ID: <xmqqr329y2sm.fsf@junio-linux.mtv.corp.google.com>
In-Reply-To: <xmqqvarly8hn.fsf@junio-linux.mtv.corp.google.com>

Junio C Hamano <gitster@pobox.com> writes:

Show 21 quoted lines

>> +	dirname = relative_path(xgetcwd(), one_up, &sb);
>
> So, the idea is we start at the root level of the current project's
> working tree, and we go up one level, then we know the last component
> of the path our submodule is bound at in the superproject.
>
>> +	prepare_submodule_repo_env(&cp.env_array);
>> +	argv_array_pop(&cp.env_array);
>> +	argv_array_pushl(&cp.args, "--literal-pathspecs", "-C", "..",
>> +			"ls-tree", "HEAD", "--", dirname, NULL);
>
> This would ask our superproject what is at the "dirname" in its
> HEAD.  Two possible issues:
>
>  - Shouldn't that be looking at its index instead?  It would be more
>    correct for unborn branch case, and new or moved submodule case.
>
>  - If our submodule is bound at path sub/dir in the superproject,
>    the relative-path thing above would get "dir" and this ls-tree
>    ends up asking what is at "dir", but the question you really want
>    to ask is what is at "sub/dir", isn't it?

IOW, the basic ontline of the idea may be OK, but I think you would want to do something along this line:

    - chdir to .. from the root of your submodule working tree;
    - in that .. directory, ask what prefix it is (you'd get
      "sub/dir", or "not a git" if you are not a submodule);
    - in that .. directory, ask ls-files what sub/dir is;
    - if it is 160000, you're happy.