Re: [PATCH] dir: fix negative pathspecs in 'git ls-files' and 'git add'

Diogo Castro [off-list ref] writes:

I don't think so.

As far as I can tell, the "strip the common prefix" feature is a
performance optimization aimed at avoiding walking the working
directory needlessly.
So for `git add -- a/b/c a/b/d`, there's no need to look anywhere
other than in `a/b/`.

But extending the "strip the common prefix" to negative pathspecs
could end up negating the benefits we get from this perf optimization.
E.g. in `git add -- a/b/c a/b/d ':!*.md'`, there is no prefix common
to *all* pathspecs, so we'd revert to walking the entire working
directory, even though `a/b/` would still suffice.

I was wondering more about case like this:

    $ git add -- a/b/c a/b/d ':!a/b/x

I agree that it is nonsense to compute the common prefix over only
positive ones, and then to strip the common prefix from both
positive and negative ones, and it needs to be corrected.