[llvm-dev] RFC: Dealing with out of tree changes and the LLVM git monorepo

[David Greene via llvm-dev]

Mehdi AMINI <joker.eph at gmail.com> writes:

> Yes, but that's the case for the zipper repo anyway: one merge per
> commit. The point is that the second commit is just a trivial merge,
> it wouldn't show up in a file `git log` for example.
> In the linear rewritten monorepo, adding the history taken from the
> existing git mirror would lead to duplicated commits, as in
> *identical* commit / commit with the same diff but different git
> hashes. I'd expect git log to show us the two commits in the git log
> of a single file.

Would it be valuable to have a tool to take branches from existing git
mirrors and rewrite them in terms of the monorepo so there would be no
duplicate commits and everything would appear to have been done against
the monorepo?

I know Justin is worried about hashes in old e-mails being invalid, but
the tool could include the mapping from old hash to new hash in the
commit message.  Of course that would only be done for local downstream
commits, as the monorepo commits were already rewritten without
including that information.  Would it be helpful to have the monorepo
commits contain that information?

                            -David