Added plugin for formatting Java sources using Palantir

[ajaychandran]

Added contrib.palantir.JavafmtModule for formatting Java sources using Palantir.
The plugin also supports command line arguments for

• checking for formatting errors with --check flag
• formatting specific files or folders

Resolves #3448.

[ajaychandran]

@lihaoyi
Is the naming convention fine?
Are there any additional features that must be implemented?

[lihaoyi]

Looks good overall, just need a few tweaks. Need a short readme.adoc in the contrib module folder, and an example test in example/javalib/linting/ next to checkstyle and errorprone to demonstrate usage.

[ajaychandran]

@lihaoyi Please review.

• The JVM args for Java 16+ do not seem to affect the behavior when using a lower Java version (tested with Java 11).

[lihaoyi]

We should also show off the ./mill mill.contrib.palantirjavaformat.PalantirJavaFormat/ workflow, and after formatting is run we should run check again and ensure it does not error like it did before

[ajaychandran]

Updated. Please review.

[ajaychandran]

Had to remove check examples.

 Incomplete argument --check <bool> is missing a corresponding value
  Expected Signature: palantirformat
    --check <bool>
    sources <str>...
  

  ,)

[lihaoyi]

I edited a comment earlier to say this, but let's standardize the naming convention of palantirformat/PalantirFormat. I know it doesn't quite match the palantir-java-format project name, but using the full name over and over is getting verbose enough I think we should shorten it here just for ease of use

[ajaychandran]

@lihaoyi
How about palantirjavafmt? Get a lot more clarity with the addition of a single character.

[lihaoyi]

Let's go with palantirformat, googling palantir format brings up only this one project, so there shouldn't be any ambiguity for now

[lihaoyi]

One consideration is that I may want to move this directly into javalib, just like how ScalaFmtModule is in scalalib and KLintModule is in kotlinlib. That way it'll be mill.javalib.palantirformat which should be unambiguous enough

[ajaychandran]

Where would the documentation go in this case? docs/modules/ROOT/pages/Java_Module_Config.adoc?

[lihaoyi]

Left some comments

The tests are failing because we need to wire up contrib.palantirformat into our dist so it will get properly published during integration testing. Should just involve adding it to the list here along with the other integration-tested contrib modules

mill/build.mill

Line 727 in 2dc343f

def testTransitiveDeps = build.runner.testTransitiveDeps() ++ Seq(

[lihaoyi]

I think this looks great, two small nits in the example and I think we can merge this and close out the bounty

[lihaoyi]

Thanks @ajaychandran! will transfer the bounty using the same details as earlier