Switch to declarative package management

[gipert]

I've been mainly following recommendations from here: https://scikit-hep.org/developer/packaging

• packaging instructions are now contained in pyproject.toml, setup.cfg (and few lines in setup.py to be backward-compatible)
• package source has been moved below src/ as recommended: simplifies packaging by a lot
• the pygama version is now managed by setuptools, which computes a git-describe-like version string automatically. I didn't know about this before and I consider it robust enough (requires just a couple of extra configs in pyproject.toml and no extra custom logic). We will not need to manually advance the version string anymore.
• export only pygama version string as LH5 object

Still to do:

• update after Address some testing and packaging issues #255 is merged
• update contributing guide
• update GHA workflow
• add missing optional dependencies (such as pyfcutils)

@jasondet: are you OK with moving the source below src/? Do you have any particular development requirement/need?

To be merged after #255

[gipert]

I'm done with this PR – let me know what you think @jasondet @iguinn and feel free to merge, if no objections. legend-exp/pyfcutils#2 should be merged too to make fcutils install seamlessly.

[jasondet]

oh wow. this looks like a good idea to me. I've requested that @iguinn and @wisecg review it.

[wisecg]

Wow! I'm impressed at the work here. I support any change that makes pygama more aligned with best practices in ScikitHEP. Eventually it would be great to publish this package with them.

The only thing I note here is that we would move the "pygama" dir one level down, to "src/pygama". As long as Luigi feels that's necessary, I'll support his decision.

[gipert]

Wow! I'm impressed at the work here. I support any change that makes pygama more aligned with best practices in ScikitHEP. Eventually it would be great to publish this package with them.

I guess it would be nice to contact them at some point, yes: https://scikit-hep.org/affiliated. But ultimately it will depend on pygama's ability to be not-so-much LEGEND-specific.

The only thing I note here is that we would move the "pygama" dir one level down, to "src/pygama". As long as Luigi feels that's necessary, I'll support his decision.

Yes, it's generally highly recommended as most tools assume this structure by default (and therefore no extra configuration is needed): https://scikit-hep.org/developer/pep621#package-structure

[jasondet]

ok. I'm going to merge this...