Create a top-level pants_release package.

[benjyw]

Move release.py and the files it imports from build-support
into the new package.

build-support was originally intended for lightweight scripts,
but it now contains non-trivial code that imports other code
from build-support.

Unfortunately, since build-support/bin is a source root, this
means that the imports aren't namespaced under anything
pants-specific. This change fixes that.

[kaos]

there's also the idea to keep the code in build-support/bin/pants to have both the namespacing and the separation from the "real" pants code.

[benjyw]

there's also the idea to keep the code in build-support/bin/pants to have both the namespacing and the separation from the "real" pants code.

A) I would argue this is real code
B) How would we make sure names under this pants don't collide with names in src/python/pants? We'd have to insist on a unique subpackage, like pants.release, at which point why not put it under src/python to enforce that?
C) This is still separated in its own top-level package

We discourage our users from artificially splitting up the repo into multiple source roots, since Pants provides the tooling to not have to do that. I suggest we follow our own advice!

BTW, I would still prefer src/python/pants/release as, again, this is real code. But I can tolerate src/python/pants_release.

Happy to bikeshed that last point though.

[cognifloyd]

Should this be pants_release or something like pants_build_support which hints at its intended usage in the build-support directory?

[benjyw]

"release" is succinct and fairly descriptive. "build-support" is a rather fuzzy term, since all of Pants is for "build support", it's not obvious that this means "support for building pants itself". And in any case, build-support is in fact about releasing...