Revert "fetchgit: take postCheckout to allow gathering revision and commit metadata without leaving .git"

[RaitoBezarius]

Reverts #465497 due to incomplete backward compatibility for tag fetching which seemed intended.

[RaitoBezarius]

@philiptaron As you merged the original PR, can you please take a look at this revert? Thank you.

[qubitnano]

Several packages now need fetchTags explicitly enabled since this commit

#473003

#473002

#473067

[RaitoBezarius]

I don't think that the solution is to add fetchTags, given this is a non backward compatible change.

[me-and]

From a small sample, it looks like the repositories that have been affected here are ones that are using deepClone and therefore implicitly leaveDotGit. Per https://nixos.org/manual/nixpkgs/stable/#fetchgit, this should only be used for testing purposes unless the .git directory is removed in the postFetch phase, and per #8567 the .git directory is known to be non-deterministic even without any changes in the fetcher.

IMVHO, the fix here is not to back this change out: backwards-incompatible changes are sometimes necessary, particularly when they're to function that is explicitly unstable. The correct fix here is for the affected derivations to make use of the new postCheckout hook to get a stable derivation without the .git directory being included in the output.

That being said, I think there should be a release note for this change to direct people to use postCheckout rather than leaveDotGit. And possibly, as I suggested in #8567, adding an evaluation warning anywhere leaveDotGit is still used.

[ShamrockLee]

due to incomplete backward compatibility for tag fetching which seemed intended.

The incompatibility is not intended. Let me fix it.

Update: I pushed the fix to PR #473411.

[ShamrockLee]

@RaitoBezarius I merged the fixing PR #473411. Please test again if the incompatibility persists.