HEAD can get out of sync

[tiennou]

See for example, git_commit_create_v, whose "Defined in" link points to https://github.com/libgit2/libgit2/blob/HEAD/include/git2/commit.h#L357-367, while the correct answer is https://github.com/libgit2/libgit2/blob/b05fbba394b9f2befea8b50817fd64209538e384/include/git2/commit.h#L357-367 (HEAD at the time docurium was ran).

Maybe the value of HEAD at the time the generation was done should be used instead ?