remote: handle negative refspecs in git remote show

remote: handle negative refspecs in git remote show

By default, the git remote show command will query data from remotes to
show data about what might be done on a future git fetch. This process
currently does not handle negative refspecs. This can be confusing,
because the show command will list refs as if they would be fetched. For
example if the fetch refspec "^refs/heads/pr/*", it still displays the
following:

  * remote jdk19
    Fetch URL: git@github.com:openjdk/jdk19.git
    Push  URL: git@github.com:openjdk/jdk19.git
    HEAD branch: master
    Remote branches:
      master tracked
      pr/1   new (next fetch will store in remotes/jdk19)
      pr/2   new (next fetch will store in remotes/jdk19)
      pr/3   new (next fetch will store in remotes/jdk19)
    Local ref configured for 'git push':
      master pushes to master (fast-forwardable)

Fix this by adding an additional check inside of get_ref_states. If a
ref matches one of the negative refspecs, mark it as skipped instead of
marking it as new or tracked.

With this change, we now report remote branches that are skipped due to
negative refspecs properly:

  * remote jdk19
    Fetch URL: git@github.com:openjdk/jdk19.git
    Push  URL: git@github.com:openjdk/jdk19.git
    HEAD branch: master
    Remote branches:
      master tracked
      pr/1   skipped
      pr/2   skipped
      pr/3   skipped
    Local ref configured for 'git push':
      master pushes to master (fast-forwardable)

By showing the refs as skipped, it helps clarify that these references
won't actually be fetched.

This does not properly handle refs going stale due to a newly added
negative refspec. In addition, git remote prune doesn't handle that
negative refspec case either. Fixing that requires digging into
get_stale_heads and handling the case of a ref which exists on the
remote but is omitted due to a negative refspec locally.

Add a new test case which covers the functionality above, as well as a
new expected failure indicating the poor overlap with stale refs.

Reported-by: Pavel Rappo <pavel.rappo@gmail.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>