Add detect-rtl-changes action

[colluca]

TODO

• Test in gitlab-ci: Use detect-rtl-changes script axi#433

[Xeratec]

For this PR, I would love to get a second review from someone working more closely with RTL. @fischeti, would you do me the honor?

In any case, I have some questions:

1. I assume the idea is to trigger, e.g., an RTL recompilation if some dependencies have changed, right?
2. In the example linked (GitLab workflow) the script seems to only detect changes in .gitlab-ci.yml and scripts/compile_vsim.sh.
   • Do you have an example where actual RTL changes are detected to test this workflow more thoroughly?
   • If possible also provide a test on a GitHub repo.

[fischeti]

1. I assume the idea is to trigger, e.g., an RTL recompilation if some dependencies have changed, right?

At least in axi, the idea is to avoid running long simulations on specific modules, if non of the source files of said module has changed. I think it makes sense for those kinds of repositories, where you have a lot of modules, but usually, you only change one module at a time.

The implementation also looks good to me. A bit complicated since it is a lot of bash stuff, but it makes sense to me and I also don't really see a simpler way to do it.

The only caveat is maybe that this is not so much used as a github action, but more for the Gitlab CI, because at the moment, I can't really think of a repository that could use this in its open source pipeline.

But I think it is a great use of the new bender+slang feature🤓

[colluca]

I agree that the script is quite ugly and complex, but I don't think we can do much better with shell syntax.

I could write it in Python instead, surely the argument parsing logic will be much simplified. But the opposite will probably happen with the subcommand invocation code.