On Sat Nov 16, 2024 at 04:36, Jeff King [off-list ref] wrote:

On Fri, Nov 15, 2024 at 09:34:28AM -0500, Caleb Cushing wrote:

quoted

Context: recently I've been trying to develop a feature for my Gradle
plugin that derives a semantic version from git describe.  In order to
achieve my next level of feature I need the HEAD Branch. Now, I can
get this branch using git remote show <remote> and parsing the output.
I'm a firm believer that it should be possible for me to write code,
long term even, without the internet; I did this once with my job when
I needed to go home to my parents who were very rural and didn't have
internet; I was able to keep working without access. I want that for
anyone that uses this tool.

You should use the refs/remotes/<remote>/HEAD symref instead (or its
alias, just "<remote>"), which is more convenient and doesn't hit the
network. Which is exactly what...

quoted

Problem: I don't want to have to do a network request every time I do
a build, in fact I'd rather almost never have to do a network request.
Gradle makes reducing the network request to less than once per build
something ... unsupported. jgit doesn't expose support for fetching
this information. Then I found out that you could do `git remote
set-head <remote> <branch>` which appears to behave exactly how I'd
want and expect. It doesn't easily solve my problem though because I
want my solution to be generally applicable.

...set-head will set. So OK, but...

quoted

Ideal Long-Term Solution: git remote set-head happens automatically on
lone, and even fetch if it's not set. Explicit setting would override
any automatic setting; and it might be a good idea to automatically
unset if the HEAD branch disappears from the remote.

We already do the equivalent of set-head on clone. If you do:

  git clone https://github.com/git/git
  cd git
  git symbolic-ref refs/remotes/origin/HEAD

you should see it pointing to "refs/remotes/origin/master" (and like you
can refer to "origin/HEAD" or "origin" from git-log, etc). Are you not
seeing that?

We don't update it on fetch. That has been discussed, but there are some
questions about when it should overwrite what's available locally. E.g.
this thread:

  https://lore.kernel.org/git/D3HBD7C1FR14.74FL1Q1S9UCB@ferdinandy.com/ (local)

That part we already have pinned down: fetch will only update remote/HEAD if it
doesn't already exist. So running "init && remote add && fetch" should end you
up in the same place as "clone" (although fetch will report if the remote has
changed HEAD compared to what you have for transparency). If you _always_ want
to have the latest head you'll need to run "fetch && remote set-head --auto
[remote]" every time.

Something like
	git fetch --all && git remote | xargs -i git remote set-head -a {}
covers everything.

There have been some patches in that direction but I have not kept up
with the current state:

  https://lore.kernel.org/git/20241023153736.257733-2-bence@ferdinandy.com/ (local)

There's definitely going to be another round, but I think (hope :)) we're not
very far off from finishing.

Best,
Bence