Nix abstraction for modifying sources

Nix has abstractions for about any built scenario as long as the output generates a store path.

In the context of driving whole repositories and developmemt emvironment with nix (not only the build), I wonder:

What would be a good enough abstraction to modify the repo’s source (in stead/addition of the nix store)?

Use case:

Code generators, such as go makes heavy use of. But also a quick rendering of markdown filw from sources in a nix job.

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nix just runs what you specify, and it can create arbitrary stuff, as long as the output goes to the store.

So a derivation that takes your source, augments it with auxiliary files to create a store path entry, or compiled sources even, which then can be used as the source for another derivation is not only possible, but quite common.

Just take a look at all the “wrapped”/“unwrapped” package pairs.

@NobbZ Thanks for the pointers! I think there is a misunderstanding involved, though:

To be clear: the target of the generated sources is not another derivation but a git commit.

I kind of get a sense, that there is no abstraction in nix for this use case. I can always do a thin bash wrapper of course, but that would prohibit semantics such as nix build (without being wrapped in a bash script that is allowed to modify paths outside of the nix store).

Or am I misunderstanding something? :wink: