git plugin's track-tags option isn't enough for gnulib's git-version-gen

[abderrahim]

When the track-tags option of the git plugin is enabled, it generates a slimmed-down .git directory enough for git describe and git log to succeed.

However gnulib's git-version-gen script relies on git log . which doesn't work, and returns an error like

fatal: unable to read tree 1bdaa2ce628b458ab6a7c9e03023a9aed221cf75

[nanonyme]

Looks like simply writing .tarball-version is enough to convince git-version-gen to do nothing.

[nanonyme]

Turns out there are bootstrap commands where this workaround doesn't really work.

[nanonyme]

Reading https://github.com/coreutils/gnulib/blob/master/build-aux/git-version-gen#L157 it looks like it's mostly only using this to test that there is a commit. Git log doesn't need to show more things than the single commit.

[abderrahim]

Essentially what I noticed (and implemented for https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/merge_requests/9009) is that to get every corner case covered (mainly git log -1, git log -1 ., git describe --dirty), you need to add all tree objects. Basically a shallow clone until the tag, with all blob objects removed (and with loose objects for reproducibility)