[PATCH 0/8] fetch: refactor code that prints reference updates

Hi,

at GitLab, we want to gain more control over fetches to achieve two different things:

    1. We want to take control of the reference updates so that we can
       atomically update all or a subset of references that git-fetch
       would have updated.

    2. We want to be able to quarantine objects in a fetch so that we
       can e.g. perform consistency checks for them before they land in
       the main repository.

To do this, we aim to use git-fetch(1)'s `--dry-run` mode with a manually set up quarantine directory. One issue we currently face though is that git-fetch(1), to the best of my knowledge, has no mode in which it would print all reference updates in a machine-parseable format.

I thus set out to implement a "porcelain"-style mode for git-fetch(1) that surfaces this information:

    - The reference that would be updated.

    - The remote reference this is coming from.

    - The old and new object IDs of the reference.

    - Whether there's any error, like a D/F conflict.

I had a hard time understanding the current implementation of how ref updates are printed though. So as a first step towards such a porcelain mode this patch series refactors said code. It sets out to achieve two major goals:

    - There should be as few global state as possible. This is to reduce
      confusion and having to repeat the same incantations in multiple
      different locations.

    - The logic should be as self-contained as possible. This is so that
      it can easily be changed in a subsequent patch series.

This patch series does exactly that, but does not yet introduce the new machine-parsebale porcelain mode.

Patrick

Patrick Steinhardt (8):
  fetch: rename `display` buffer to avoid name conflict
  fetch: move reference width calculation into `display_state`
  fetch: move output format into `display_state`
  fetch: pass the full local reference name to `format_display`
  fetch: deduplicate handling of per-reference format
  fetch: deduplicate logic to print remote URL
  fetch: fix inconsistent summary width for pruned and updated refs
  fetch: centralize printing of reference updates

 builtin/fetch.c | 270 ++++++++++++++++++++++++------------------------
 1 file changed, 134 insertions(+), 136 deletions(-)