Allow hyphen - in legal workspace names

[antlauzon]

I don't see how directories with a hyphen aren't legal workspaces. Please consider adding support for names with hyphen in them to master or provide a reason why hyphen can't be used.

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[damienmg]

This was a decision following https://docs.google.com/document/d/1skNx5o-8k5-YXUAyEETvr39eKoh9fecJbGUquPh5iy8/preview. Hyphens in directories are problematic in some languages (e.g, python) and should be replaced by _ in workspace names.

[antlauzon]

What abouit java and npm packages? I think this PR should be better addressed.

[kchodorow]

I know this is inconvenient, but hyphens are also not allowed in Java package names.

[antlauzon]

It's extremely inconvenient. For instance, I have a special macro that specifies metadata for NPM tarballs. In it, I now have to do shenanigans like:

target_name = name.replace("-", "_")
metadata['name'] = target_name
url = 'http://registry.npmjs.org/%s/-/%s-%s.tgz' % (name, name, version)
return metadata

Not okay.

[antlauzon]

Another problem is that I can't require any of my node modules from the external directory now without first writing a rule that either a) renames all the directories to change _ to - or b) symlinks everything with a _ to its - cousin. What a mess.