builtin/maintenance: introduce "geometric" strategy

Hi,

by default, git-maintenance(1) uses git-gc(1) to perform repository housekeeping. This tool has a couple of shortcomings, most importantly that it regularly does all-into-one repacks. This doesn't really work all that well in the context of monorepos, where you really want to avoid repacking all objects regularly.

An alternative maintenance strategy is the "incremental" strategy, but this strategy has two downsides:

• Strategies in general only apply to scheduled maintenance. So if you run git-maintenance(1), you still end up with git-gc(1).

• The strategy is designed to not ever delete any data, but a full replacment for git-gc(1) needs to also prune reflogs, rereree caches and vanished worktrees.

This patch series aims to fix both of these issues.

First, the series introduces a new "geometric" maintenance task, which makes use of geometric repacking as exposed by git-repack(1) in the general case. In the case where a geometric repack ends up merging all packfiles into one we instead do an all-into-one repack with cruft packs so that we can still phase out objects over time.

Second, the series extends maintenance strategies to also cover normal maintenance. If the user has configured the "geometric" strategy, we'll thus use it for both manual and scheduled maintenance. For backwards compatibility, the "incremental" strategy is changed so that it uses git-gc(1) for manual maintenance and the other tasks for scheduled maintenance.

Thanks!

Patrick

To: git@vger.kernel.org Cc: Derrick Stolee stolee@gmail.com Cc: Taylor Blau me@ttaylorr.com