feat: Formatter

[sh0rez]

Adds a tk fmt command that basically exposes what's know as
jsonnetfmt: A formatter for Jsonnet.

Did some work around actually finding files to format, think it looks good.

Semantics:

• only works on .jsonnet and .libsonnet, unless specified explicitely
• ignores hidden files, and vendor
• tk fmt <directory>: reformat every jsonnet file recursively
• tk fmt <file>: reformat that file
• tk fmt --stdout: print to stdout instead of writing to disk
• tk fmt --test: exit with non-zero in case of differences. Does not
  touch files

[malcolmholmes]

I tried this on an un-linted Jsonnet codebase. Running tk fmt did nothing. tk fmt lib did nothing. tk fmt --help gave me help output, suggesting I'm using the right version. Is this my mistake, or a fault with the code?

[sh0rez]

I tried this on an un-linted Jsonnet codebase. Running tk fmt did nothing. tk fmt lib did nothing. tk fmt --help gave me help output, suggesting I'm using the right version. Is this my mistake, or a fault with the code?

Added some more bad usage handling and a verbose mode:

• it now fails when not specifying anything
• --verbose / -v prints all files and whether they are reformatted
• prints a message if all files are already okay

[sh0rez]

ping @malcolmholmes @rfratto, had success using this the last week, sb wanna approve?

[malcolmholmes]

Completion: tk fmt e<tab> gives tk fmt env not environments. Why?

[malcolmholmes]

This shouldn't block, but the thing that is missing for me is a "lint diff". i.e. show me what you would change. --stdout (which should have a short switch) doesn't tell me what changed (other than the number of files). Otherwise, this seems to be behaving as described.

[sh0rez]

Completion: tk fmt e<tab> gives tk fmt env not environments. Why?

because go-clix@v0.1.0 had an issue, fixed it in go-clix@v0.1.1