Re: [PATCH v3 2/5] setup: allow for prefix to be passed to git commands

From: Brandon Williams <bmwill@google.com>
Date: Mar 20, 2017, 22:34 UTC
Message-ID: <20170320223418.GB188475@google.com>
In-Reply-To: <xmqqinn761f7.fsf@gitster.mtv.corp.google.com>

On 03/17, Junio C Hamano wrote:

Show 11 quoted lines

> Brandon Williams <bmwill@google.com> writes:
> 
> > I don't think that prefix can ever have ".." in it.  From what I
> > understand it is always a path from the root of the repository to the
> > cwd that the git command was invoked by.  So in your example prefix
> > would be "src/".
> 
> The prefix would be NULL or "", as you will be at the root-level of
> the working tree when you are running _IN_ the submodule (by
> recursing into it).  Not src/, nor anything with ../ in it, I would
> think.

Yes, the prefix that is found during setup of a submodule process would be NULL or "" as the command would be invoked from the root of that repository. This series would sort of change that though.

If a command was invoked from 'src/' with a pathspec of '../dir/' and there is a submodule at 'dir/sub', the process working on the submodule will have the following:

super_prefix = 'dir/sub/'
prefix = 'src/' (Passed from the parent process via the
                 GIT_INTERNAL_TOPLEVEL_PREFIX env var)
pathspec = '../dir/'

With that information the child process will be able to properly resolve the pathspec to be 'dir/' (using the prefix) and will be able to match against it by pre-pending the super_prefix (e.g. dir/sub/some/file, where some/file is a file in the submodule). It will also be able to generate correct output relative to the directory the command was originally invoked from by first pre-pending the super_prefix so we have 'dir/sub/some/file' and then calling relative_path() with the prefix that was passed in such that the output for this file looks like '../dir/sub/some/file'

That the gist of how I'm hoping to solve the problem. Hopefully that was clear enough to get some feedback on.

-- 
Brandon Williams