Reuse package output for new package

[phodina via <help-guix@gnu.org>]

Hi,

is there a way to create a new package by reusing the output of the original derivation and just add files to the new package into the new output?

The usecase is PhotoGimp [1] which is set of files which are added to an already built gimp package.

There standard way is to inherit the package and add these files but that will result in rebuilt, right?

Alternative idea is to use copy-build-system and copy the already created package files into the output. Then just add additional files.

However, there's also a draw back if the original package contains hardcoded variable. But this would be only problem if I specify something in the #:phases, correct?

The main idea here is to save the computing resources on packages that take long time and their behviour can be changed by plugins/config files etc.

Of course the simplest way to use [1] it is to unpack the content of the home dir but IMHO that's not the correct way how to package this program.

[1] https://github.com/Diolinux/PhotoGIMP

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Petr