Re: [PATCH 0/5] ff-refs: builtin command to fast-forward local refs

Jeff King [off-list ref] writes:

On Wed, Nov 18, 2015 at 10:56:02AM +0100, Johannes Schindelin wrote:

quoted

quoted

For me I use this command more as a post-fetch:

git fetch --all --prune && git-ff-refs

I imagine that the big difference is in the number of branches that I
maintain, and perhaps in the way that I use gitk to visualize them.  I
would be happy to add another option to git-fetch for --ff-refs as an
alternative if that would feel better than a full-on builtin.

I would much prefer, say, `git fetch --all --prune
--fast-forward-tracking-branches` (with maybe `-T` as short option for
`--fast-forward-tracking-branches` and/or a shorter `--ff-tracking`) to a
new builtin.

Hmph, I am not sure it is a good idea to allow "git fetch" affect
refs that it was not told to "fetch", but that is why you give a new
option from the command line to update refs that are not involved in
the fetch based on what was fetched, so it might be OK.

But the above is *NOT* fast-forwarding "tracking" branch.  It is
doing something else: fast-forwarding the local branch that is based
on a remote-tracking branch.

    They have refs/heads/master, and they call it their 'master'
    branch.

    You have refs/remotes/origin/master, and that is the
    remote-tracking branch for their 'master'.

    You may have prepared your 'master' to build on their 'master'
    branch.  That is not a 'tracking branch' for anything.

So --ff-tracking and the other name above need to be rethought.

FWIW, that makes a lot more sense to me, as it would presumably touch
only branches which track whatever we just updated, and not other random
refs.

This ff-refs series breaks build for me by introducing calls to chdir()
whose return values are not checked -Werror=unused-result, by the way.

I have to admit that I'm a little wary of something like ff-refs meeting
all needs, though. I have custom scripts that match my workflow and tell
me when a branch could be updated. I could replace part of them with
"ff-refs --dry-run", but that is really not much code. Basically:

  git for-each-ref --format='%(refname) %(upstream)' refs/heads |
  while read ref upstream; do
    git merge-base --is-ancestor $ref $upstream &&
      echo "$ref can fast-forward"
  done

Yup.  I like that one.