-----Original Message-----

On Monday, May 29, 2023 9:39 AM, Paul Jolly wrote:

I would appreciate some advice on the best way to solve the following problem.

As part of my project, I have a code generation script that sha256 hashes a number of
files to another file. This produces a deterministic "has this part of the project
changed" indicator via the code generated file's content, that I then use in various
cache invalidation steps.

This means, however, that I need to re-run that code generation script as part of each
commit in order to ensure that the code generated hash file is current (I have a step
in CI that detects if it is not, which re-runs the code generation script to then see if
the commit is "clean").

As part of my development setup I do a lot of interactive rebasing to edit earlier
commits in a branch (these "stacks" of changes are reviewed via Gerrit, which
understands a relation chain of changes).
Via this workflow, I often do a git rebase and edit an earlier commit in such a way
that I need to re-run the code generation script.

The challenge is that any commit in such a "stack" of commits might need me to re-
run the code generation script. But I clearly don't want to do this manually!

What I'm looking for is a way to automatically re-run this code generation script
when I commit changes, or perform a rebase-edit step etc.

I've tried to experiment with how I might do this using git commit hooks. But so far,
my git foo is failing me. It mainly fails because when doing an edit of an earlier
commit via an interactive rebase, later changes might well conflict (in the generated
file) with the results of the code generator having been re-run on the edited commit.
At this point, my git rebase --continue stops until I have fixed the conflict. But in
almost all situations, the conflict comes in the generated hash file. Which I fix by
simply re-running the code generation script (I could optionally fix it by doing a git
checkout --theirs, and then re-running the code generation script).

This all feels tantalisingly close to being a perfect workflow! But I can't quite figure
out how to make the git hooks "work" in such a way that doesn't require any
intervention from me (except in those situations where there is a conflict during the
rebase that is _not_ in the code generated file and so does require my intervention).

The code generation step is incredibly fast if there is nothing to do, and is quite fast
even when there is something to do (in any case it can't avoid doing this work).

Please can someone help nudge me in the right direction?

I wonder whether setting up a clean/smudge filter might help. You might want to look into a clean filter that runs your code generator.

--Randall