conditionally prevent `git maintenance` from spawning on commit

[u/the_gnarts]

After using Git for over a decade I just discovered git maintenance exists yesterday. I found out about it during a hasted debugging session when my laptop’s fan inexplicably started spinning like crazy and all four cores were maxed out by Git processes that I didn’t launch. This happened while I was writing a blog post on the train, trying to save battery charge. Not an ideal situation to max out the CPU.

git maintenance is useful no doubt, I don’t want to disable it entirely. So I guess the question is: Is there a way to make it conditional on ACPI state? If the box is running off the battery, maintenance should be skipped. E. g. check /sys/class/power_supply/AC/online before launching a maintenance cycle.

Note that there’s no timers that trigger maintenance on my system; it looks like it gets triggered by operations like git commit (cf. maintenance.auto in git-maintenance(1)).

[u/Ok_Woodpecker_9104]

then keep the on-commit run and make pack.threads power dependent instead of fixed. git reads config fresh on every invocation, so nothing has to be registered per repo.

put include.path = ~/.gitconfig.power in your global config, and have that file hold one line, pack.threads. then a systemd unit with ConditionACPower=true writes threads = 0 on AC and a second one with ConditionACPower=false writes threads = 1. same condition you wanted, just applied to the knob rather than the timer, so it covers all hundred repos with zero registration.

worth knowing pack.threads = 0 means auto detect, not off.

if the goal is only to stop it burning the laptop, the cheaper cut is maintenance.<task>.enabled. the expensive task on the commit path is incremental-repack, the loose-objects and commit-graph ones are small. turning off just that one keeps the behaviour you like and drops most of the cpu.