Add buf linter and fixer

[amckinney]

This adds the buf lint command as a linter and the buf format command as a fixer. The buf lint linter was previously published from our own vim-buf repository here, whereas the buf format fixer is completely new. We'd like both of them to exist in ale now that buf has a stable v1 release.

I've included a description and test for each (pattern matching from what previously exists, e.g. clang-format, dartfmt, and gofmt). I've also verified that both work locally by pointing vim-plug to my local copy of ale.

I've used the following .vimrc configuration to test locally against .proto files:

let g:ale_linters = {
\   'proto': ['buf-lint'],
\}
let g:ale_lint_on_text_changed = 'never'
let g:ale_linters_explicit = 1

let g:ale_fixers = {
\   'proto': ['buf-format'],
\}
let g:ale_fix_on_save = 1

[amckinney]

Thanks for the reviews @w0rp and @hsanson! This should be ready for another look.

[amckinney]

It looks like we're seeing a lint failure for the name of the buf-lint linter:

========================================
Running custom linting rules
========================================
Custom warnings/errors follow:

ale_linters/proto/buf_lint.vim: Use snake_case names for linters

Is there any way we can make an exception for this one? Given that we're migrating the linter from vim-buf, this would be a breaking change for anyone that removes the dependency on vim-buf and instead uses ale directly - they would need to update the following configuration:

let g:ale_linters = {
\   'proto': ['buf-lint'],
\}

Plus, I noticed that there is already a protoc-gen-lint linter in here and it appears that kebab-case is allowed for it (here). I searched around for an exception list (one that would include protoc-gen-lint), but I can't seem to find it anywhere.

[hsanson]

@amckinney what you can do is set the name using snake case and add an alias. See "cabal_ghc" for example:

call ale#linter#Define('haskell', {
\   'name': 'cabal_ghc',
\   'aliases': ['cabal-ghc'],
\   'output_stream': 'stderr',
\   'executable': 'cabal',
\   'cwd': '%s:h',
\   'command': function('ale_linters#haskell#cabal_ghc#GetCommand'),
\   'callback': 'ale#handlers#haskell#HandleGHCFormat',
\})

[amckinney]

Thanks for the tip @hsanson, I added the alias and everything works on my end.