Limit refspecs to "recent" pull requests

[DamienCassou]

I'm working on a project with more than ten thousand PRs: 25 are currently open and they are within the most recent 500 ones. Listing branches in magit is quite slow because of all the refs/pullreqs refspecs.

To make this faster, I started filtering the refspecs that are fetched:

[remote "origin"]
	fetch = +refs/heads/*:refs/remotes/origin/*
	fetch = +refs/pull/*/head:refs/pullreqs/*
	fetch = ^refs/pull/2*/head # don't fetch old PRs
	fetch = ^refs/pull/3*/head # don't fetch old PRs
	fetch = ^refs/pull/4*/head # don't fetch old PRs
	fetch = ^refs/pull/5*/head # don't fetch old PRs
	fetch = ^refs/pull/6*/head # don't fetch old PRs
	fetch = ^refs/pull/7*/head # don't fetch old PRs
	fetch = ^refs/pull/8*/head # don't fetch old PRs
	fetch = ^refs/pull/9*/head # don't fetch old PRs

This filters out all PRs that don't start with a "1". This works because all recent PRs (those greater than #12131) start with a "1".

Then I cleaned all PR refspecs with:

$ git for-each-ref --format='delete %(refname)' refs/pullreqs | git update-ref --stdin

Then I launched forge-pull again to fetch again all PR refspecs starting with a "1".

This makes magit much faster but is very hackish. Do you have any idea on how to do better?

[tarsius]

Listing branches in magit is quite slow because of all the refs/pullreqs refspecs.

What exactly gets slower? magit-show-refs?

git for-each-ref "--format=... refs/heads (using the same format as magit-insert-local-branches) takes 0.3 seconds instead of 0.12 for https://github.com/NixOS/nixpkgs. Is that the slowdown you are experiencing, or do you see a bigger effect? (I haven't imported any api data into forge.)

magit-status takes quite a while. Unfortunately I forgot to time before adding pull-request refspec, so I am not cloning a second time. (Which takes a while.)

[DamienCassou]

magit-checkout for example was very slow to list branches to switch to.

But, following your question, I have done more tests and I have no clue what is happening anymore. For example, on the nixpkgs repository, magit-checkout takes between 1 second and around 7 seconds to list only 661 refs. Why these differences in speed?

It seems that one slow thing is magit-get-previous-branch:

(benchmark-call
  (lambda ()
    (let ((default-directory "/home/cassou/Documents/projects/nix/nixpkgs-master"))
      (magit-get-previous-branch)))
  20.0)

This results in (21 36.658059883 0 0.0) showing that each call to magit-get-previous-branch takes around 1s.

[tarsius]

I'll look into that function, but it will have to wait until I am less busy.