[flang-dev] Rewriting f18's history for inclusion in llvm monorepo

[Peter Waller via flang-dev]

Hi List,

Following on from previous conversations about integrating f18 with the 
llvm monorepo, we wanted to preserve as much history as we can, but also 
to have a history without merge commits.

I've just submitted a pull request containing a "flatten.sh" which tries 
to do this. Further information is in the pull request. To help with 
review I've pushed the rewritten history up as well.

Pull request: https://github.com/flang-compiler/f18/pull/854
Example rewritten history: https://github.com/peterwaller-arm/f18/tree/new

It's not perfect yet, in particular for merge commits:

* The commit messages aren't great (yet).
* We could talk about exactly what metadata we want to preserve for merges.

For now I've assumed that the second-parent of the merge commit contains 
the relevant authorship information for the patch, so the GIT_AUTHOR_* 
is taken from this, which is the last commit before a pull request is 
merged.

Once we're happy with this in flang-dev, we can present this to llvm-dev 
and adapt the script for submission.

Your input is welcomed.

Regards,

- Peter