[0/2] Maintenance: add pack-refs task

Message

Philippe Blain via GitGitGadget Feb. 8, 2021, 2:52 p.m. UTC

This patch series adds a new pack-refs task to the maintenance builtin. This
operation already happens within git gc (and hence the gc task) but it is
easy to extract. Packing refs does not delete any data, only collects loose
objects into a combined file. This makes things faster in subtle ways,
especially when a command needs to iterate through refs (especially tags).

Credit for inspiring this goes to Suolong, who asked for this to be added to
Scalar [1]. I've been waiting instead to add it directly to Git and its
background maintenance. Now is the time!

[1] https://github.com/microsoft/scalar/issues/382

I chose to add it to the incremental maintenance strategy at a weekly
cadence. I'm not sure there is significant value to the difference between
weekly and daily. It just seems to me that weekly is often enough. Feel free
to correct me if you have a different opinion.

My hope is that this patch series could be used as an example for further
extracting tasks out of the gc task and making them be full maintenance
tasks. Doing more of these extractions could be a good project for a new
contributor.

One thing that is not implemented in this series is a notion of the behavior
for the pack-refs task during git maintenance run --auto. This could be
added in the future, but I wanted to focus on getting this behavior into the
incremental maintenance schedule.

Thanks, -Stolee

Derrick Stolee (2):
  maintenance: add pack-refs task
  maintenance: incremental strategy runs pack-refs weekly

 Documentation/config/maintenance.txt |  5 +++--
 Documentation/git-maintenance.txt    |  6 ++++++
 builtin/gc.c                         | 23 +++++++++++++++++++----
 t/t7900-maintenance.sh               | 24 ++++++++++++++++++++++++
 4 files changed, 52 insertions(+), 6 deletions(-)


base-commit: fb7fa4a1fd273f22efcafdd13c7f897814fd1eb9
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-871%2Fderrickstolee%2Fmaintenance%2Fpack-refs-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-871/derrickstolee/maintenance/pack-refs-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/871

Comments

Taylor Blau Feb. 8, 2021, 10:46 p.m. UTC | #1

On Mon, Feb 08, 2021 at 02:52:21PM +0000, Derrick Stolee via GitGitGadget wrote:
> I chose to add it to the incremental maintenance strategy at a weekly
> cadence. I'm not sure there is significant value to the difference between
> weekly and daily. It just seems to me that weekly is often enough. Feel free
> to correct me if you have a different opinion.

I don't have any strong opinion about this. At GitHub we run pack-refs
as part of a maintenance-like job, which varies in frequency between
different repositories based on a number of factors. In our busiest
repository networks, this is almost certainly at least a few times a
day, if not "as often as possible."

I'd suspect that for any laptop-sized repository, anywhere between daily
and weekly is just fine.

I suppose weekly is a good starting point, since we can always change
the default to run more often if enough users complain.

> My hope is that this patch series could be used as an example for further
> extracting tasks out of the gc task and making them be full maintenance
> tasks. Doing more of these extractions could be a good project for a new
> contributor.

That's great :-).

Thanks,
Taylor