Git 3.0 is tentatively scheduled for September 2026 and it will include
SHA-256 and reftable as the defaults for newly created repositories with
git init (and for reftable, with newly created clones of existing
repositories).  gitolite3 appears to have some changes upstream (in
3dc8093227e15434eec4924590cdf0eb63284c73) that support SHA-256
repositories, which I do not believe the present version in Debian has.

Would you be willing to update the package to a version that includes
these changes to help get Debian ready for the Git 3.0 release?  Without
those changes, I'm afraid that gitolite might not function correctly out
of the box with repositories created using Git 3.0's default settings.
I'm trying to make a haphazard attempt to get various projects ready for
Git 3.0.

I must admit I'm not very familiar with gitolite's code, but I don't
think it will need any changes for reftable since I don't think it
works with refs other than with the Git command line.  If you want to
test that, you can simply do `git refs migrate --ref-format=reftable` on
an existing repository.

I have requested the Debian git maintainer to upload a version to
experimental compiled with WITH_BREAKING_CHANGES in #1133193, which
would allow you to test the Git 3.0 defaults.