After upgrading my local Nix from 2.18 to 2.22, evaluating
Unstraightened became very slow. I think this is a bug in
Nix (https://github.com/NixOS/nix/issues/10773), and it may explain
the slowness I've been seeing in CI.
Attempt to work around this by unconditionally passing `ref` to
`fetchGit`. This seems like it should not do anything, since we also
pass a `rev` and set `allRefs = true`, but it does work around the
caching issue (mostly... it looks like submodules still hit it).
Tested locally in both Nix 2.18 and Nix 2.22. I did see some odd
warnings with 2.18 (`warning: refname
'e4031935803c66eca2f076dce72b0a6a770d026c' is ambiguous`), but only for
one refname and they did not recur. Ignore that for now.
Having CI confirm allRefs false is still safe would require a network
hit for each repo, which is already problematic. But
https://github.com/NixOS/nix/issues/7120 means we'd need to drop CI's
cached content, not just its cached refs: given how much we're fetching
that seems too much.
Fetch all refs unconditionally, assuming we're typically re-fetching the
same fixed rev repeatedly, which should be cached.
The doom profile is a non-negligible fraction of the cachix binary size,
that will only get worse (any dependency change will trigger a rebuild),
and caching them is essentially useless.
Expose emacsWithPackages so we can push just that. Skip
emacsWithPackages itself and push just the -deps derivation while we're
at it: caching either emacsWithPackages or -deps is similarly useless,
but they are a bit smaller.
When I say "non-negligible", it's about 1 MiB per "full" profile: much
larger than most individual libraries but not actually large. So this is
really a micro-optimization.
Triggered by ob-ammonite (used by scala, in emacsattic) depending on
ammonite-term-repl (also in emacsattic). `eself` only contains
emacs-overlay and doomPackageSet.
All of this needs refactoring, but an explicit recursive call fixes the
immediate problem.
CI fails to fetch it:
```
error: Server does not allow request for unadvertised object 87d0d1fb0566a80229029d0d8d7c863138d70aae
warning: could not update mtime for file '/home/runner/.cache/nix/gitv3/0gjpwip102kwcvz961gsiva3lqmmr6266s5wzs8kq0ybm68gwpx9/refs/heads/master': No such file or directory
error:
… while checking flake output 'checks'
at /nix/store/fwrwzxjvvpx1l27h8j5f9gffzwn2vdik-source/flake.nix:54:7:
53| in {
54| checks = perSystemPackages (pkgs:
| ^
55| let
… while checking the derivation 'checks.x86_64-linux.full'
at /nix/store/fwrwzxjvvpx1l27h8j5f9gffzwn2vdik-source/flake.nix:83:11:
82| })).emacsWithDoom;
83| full = mkDoom {
| ^
84| full = true;
(stack trace truncated; use '--show-trace' to show the full trace)
error: Cannot find Git revision '87d0d1fb0566a80229029d0d8d7c863138d70aae' in ref 'refs/heads/master' of repository 'https://git.savannah.gnu.org/git/emms.git'! Please make sure that the rev exists on the ref you've specified or add allRefs = true; to fetchGit.
```
Try to follow the suggestions from the error message, as I do see the
commit in https://git.savannah.gnu.org/cgit/emms.git/.
I'm not sure why this is only failing now...
I knew this might cause problems at some point, but it came to a head
sooner than expected: it triggered
https://github.com/magit/magit/issues/5131 (magit is pinned but
magit-section was not, and those packages expect to be kept in sync).
The fix is messier than I'd like but at least fixes magit.
