Support for GNU Awk linting (#638)

* GNU Awk linter support

* Documentation for awk linter

README.md

@@ -58,6 +58,7 @@ name. That seems to be the fairest way to arrange this table.
 | ASM | [gcc](https://gcc.gnu.org) |
 | Ansible | [ansible-lint](https://github.com/willthames/ansible-lint) |
 | AsciiDoc | [proselint](http://proselint.com/)|
+| Awk | [gawk](https://www.gnu.org/software/gawk/)|
 | Bash | [-n flag](https://www.gnu.org/software/bash/manual/bash.html#index-set), [shellcheck](https://www.shellcheck.net/) |
 | Bourne Shell | [-n flag](http://linux.die.net/man/1/sh), [shellcheck](https://www.shellcheck.net/) |
 | C | [cppcheck](http://cppcheck.sourceforge.net), [gcc](https://gcc.gnu.org/), [clang](http://clang.llvm.org/)|

ale_linters/awk/gawk.vim

@@ -0,0 +1,26 @@
+" Author: kmarc <korondi.mark@gmail.com>
+" Description: This file adds support for using GNU awk with sripts.
+
+let g:ale_awk_gawk_executable =
+\   get(g:, 'ale_awk_gawk_executable', 'gawk')
+
+let g:ale_awk_gawk_options =
+\   get(g:, 'ale_awk_gawk_options', '')
+
+function! ale_linters#awk#gawk#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'awk_gawk_executable')
+endfunction
+
+function! ale_linters#awk#gawk#GetCommand(buffer) abort
+    return ale_linters#awk#gawk#GetExecutable(a:buffer)
+    \   . ' ' . ale#Var(a:buffer, 'awk_gawk_options')
+    \   . ' ' . '-f %t --lint /dev/null'
+endfunction
+
+call ale#linter#Define('awk', {
+\   'name': 'gawk',
+\   'executable_callback': 'ale_linters#awk#gawk#GetExecutable',
+\   'command_callback': 'ale_linters#awk#gawk#GetCommand',
+\   'callback': 'ale#handlers#cpplint#HandleCppLintFormat',
+\   'output_stream': 'both'
+\})

doc/ale-awk.txt

@@ -0,0 +1,25 @@
+===============================================================================
+ALE Awk Integration                                          *ale-awk-options*
+
+
+-------------------------------------------------------------------------------
+gawk                                                  *ale-awk-gawk*
+
+g:ale_awk_gawk_executable                      *g:ale_awk_gawk_executable*
+                                               *b:ale_awk_gawk_executable*
+  Type: |String|
+  Default: `'gawk'`
+
+  This variable sets executable used for gawk.
+
+
+g:ale_awk_gawk_options                            *g:ale_awk_gawk_options*
+                                                  *b:ale_awk_gawk_options*
+  Type: |String|
+  Default: `''`
+
+  With this variable we are able to pass extra arguments for gawk
+  for invocation.
+
+-------------------------------------------------------------------------------
+  vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl: