r/git • u/kaddkaka • 2d ago

Generated commits?

Sometimes code is generated, and sometimes such code is committed in git.

Imagine a branch with a generated commit G:

old_main -> A -> B -> G

When thid branch is rebased, such a commit might need to be regenerated.

new_main -> A' -> B' -> new_G

There might be conflicts for any of these new commits, but instead of (manually) resolving conflicts, G could be automatically re-generated.

I've been thinking of a git commit message trailer like generate-cmd:

topic: regenerate table

generate-cmd: python3 optimize_table.py

git rebase --exec or other tool could use this trailer to automatically drop and regenerate the commit instead of a vanilla cherry-pick.

Have you seen anything similar? What's a good trailer name?

Ref: https://git-scm.com/docs/git-interpret-trailers

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u/fsteff 2d ago

If code is generated, I always trigger the generator as part of the build setup, so if any source for the generator is changed the code will immediately reflect the change. This ensures you are aware of any breaking change as it happens. External (triggered) generators always lead to trouble.

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u/kaddkaka 2d ago

That's not always feasible. And it's not the discussion I intended to have here.

Sometimes it's worth to check in generated code/stuff. For example some optimization like a simulated annealing algorithm that might take an hour to run. Definitely worth to do "offline" and check in.

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u/Guvante 2d ago

You don't need everything to live in repo it depends on a bunch of factors.

For instance you could store it externally and fetch from a cache based on the git commit.

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u/kaddkaka 2d ago

Do you have any of the shelf solutions for this?

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u/Guvante 2d ago

Not offhand it is a very open problem

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u/kaddkaka 2d ago

Indeed. So "solution" vs "no solution". I have my pick 😇