The .git/ directory takes 4 GB per build on Fedora Stable x86-64 buildbot

[vstinner]

After seeing issue gh-788, I checked the size of the .git/ directory on the Fedora Stable x86-64 buildbot worker. It takes 4.1 GB, but this size is reduced to 274 MB after running gc gc.

bash-5.3$ du -sh .git
4.1G	.git

bash-5.3$ git gc
(...)

bash-5.3$ du -sh .git
274M	.git

I see that the "ARM64 Windows" and "wasm32-wasi" buildbots use a custom Git configuration to use a shallow clone:

            git_options=dict(
                # Do a full shallow clone for every build
                mode="full",
                method="clobber",
                shallow=True,
                # Disable the default, if set
                filters=None,
            ),

Should we use a shallow clone on all buildbot workers to reduce the .git/ size? Currently, we use:

                    # "git clean -fdx": remove all files which are not tracked
                    # by Git, ignoring the .gitignore rules (ex: remove also
                    # ".o" files).
                    mode="full",
                    method="fresh",
                    # Partial (blobless) clone: only fetch commit and tree
                    # objects, blobs are fetched on demand during checkout.
                    filters=["blob:none"],

cc @zware @stratakis

[zware]

If git gc is effective, maybe we could add a post-clean step for that?