add 'bare compile' provider, for starters for use by mix

[tsloughter]

For #671

Example:

rebar3 bare compile

Note you'll need to set ERL_LIBS for any dependencies needing for compilation and plugins still go to _build/default/plugins.

[tsloughter]

Also note that it is marked to not be part of rebar3 help because it should not be something used by normal users.

[tsloughter]

@ferd I added include for each app in the escript to always be included. This would actually allow plugins to use ?PRV_ERROR without depending on providers.. Thoughts? I could revert that because it actually isn't needed after making the change to use -pz instead of -pa for the code paths.

[ferd]

I don't exactly see how it could hurt, and it keeps more stuff working I guess.

[tsloughter]

I lied, it doesn't work.

[ericmj]

This works great! Thank you!

[ericmj]

Please start semver versioning your releases also because we need a version to install rebar3 via mix. Right now I use 0.0.0-beta.2 as version.

[ferd]

We're still in beta, so semver means nothing :v

[ericmj]

Semver might not have semantic meaning for pre-releases, but it's still a useful format for version strings and version ordering specification. We use it to order versions so that we can install the latest rebar version.

[tsloughter]

@ferd, semver also just means a specific format of writing versions so tools can parse it. We rely on it as well in our vsn parsing.

[ferd]

So 3.0.0-beta.3 would be the next one. I guess we gotta switch a dash for a period in https://github.com/rebar/rebar3/blob/master/src/rebar.app.src#L6

[ericmj]

Great, thanks. Can you also use that for the tags?

[ferd]

I guess so, it's not a huge effort, but we can't retrofit old ones.

[tsloughter]

We are due a new release anyway.