The weekly maintenance would not prune refs. This is not an issue on
odoo/odoo because development branches are in a separate repository,
thus never fetched (we push to them but only using local commits and
remote refs).
However on repos like odoo/documentation the reference and development
branches are collocated, the lack of pruning thus keeps every
development branch alive locally, even years after the branch has been
deleted in the repository.
By pruning remote-tracking refs before GC-ing, we should have cleaner
local clones, and better packing.
The goal is to reduce maintenance and odd disk interactions &
concurrency issues, by not creating concurrent clones, not having to
push forks back in the repository, etc... it also removes the need to
cleanup "scratch" working copies though that looks not to have been an
issue in a while.
The work is done on isolated objects without using or mutating refs,
so even concurrent work should not be a problem.
This turns out to not be any more verbose (less so if anything) than
using `cherry-pick`, as that is not really designed for scripted /
non-interactive use, or for squashing commits thereafter. Working
directly with trees and commits is quite a bit cleaner even without a
ton of helpers.
Much of the credit goes to Julia Evans for [their investigation of
3-way merges as the underpinnings of cherry-picking][3-way merge],
this would have been a lot more difficult if I'd had to rediscover the
merge-base trick independently.
A few things have been changed by this:
- The old trace/stderr from cherrypick has disappeared as it's
generated by cherrypick, but for a non-interactive use it's kinda
useless anyway so I probably should have looked into removing it
earlier (I think the main use was investigation of the inflateinit
issue).
- Error on emptied commits has to be hand-rolled as `merge-tree`
couldn't care less, this is not hard but is a bit annoying.
- `merge-tree`'s conflict information only references raw commits,
which makes sense, but requires updating a bunch of tests. Then
again so does the fact that it *usually* doesn't send anything to
stderr, so that's usually disappearing.
Conveniently `merge-tree` merges the conflict marker directly in the
files / tree so we don't have to mess about moving them back out of
the repository and into the working copy as I assume cherry-pick does,
which means we don't have to try and commit them back in ether. That
is a huge part of the gain over faffing about with the working copy.
Fixes#847
[3-way merge]: https://jvns.ca/blog/2023/11/10/how-cherry-pick-and-revert-work/
`gc --prune` can not take a *separate* parameter, it has to be part of
the same arg (the `=` is not optional), otherwise the `gc` call blows
up.
So use the positional form of the git command to generate the correct
invocation, Python-level `foo=bar` generates a split-style option in
two args which does not please git.
Before this, we would check if a repository had a name and run
maintenance on it, leading to repeated (but unnoticed until now
because I didn't monitor it) tracebacks as the maintenance cron would
fail to find the local repo then run maintenance on nowhere anyway.
Also augment the repo-finding process to try and get better
information about what it's doing when it fails, rather than failing
completely silently.
If the stagings are going to be created locally (via a git working
copy rather than the github API), the mergebot part needs to have
access to the cache, so move the cache over. Also move the maintenance
cron.
In an extermely minor way, this prefigures the (hopeful) eventual
merging of the ~~planes~~ modules.
