Bug on `git-unix` with CentOS 7 and Oracle 7

[dinosaure]

Probably due to an old and bad version of git but git fsck fails with ocaml-git.3.4.0 (and it does not fail with ocaml-git.3.3.3) about empty commit. I suspect that the commit format was not really formalized at this time (git.1.9.0) so I need to introspect and bisect to see where is the error.

[dinosaure]

see ocaml/opam-repository#18558