#254 Add an option for logging the output of commands

test/test_ale_info.vader

@@ -41,6 +41,7 @@ After:
   unlet! g:globals_string
   unlet! g:command_header
   let g:ale_buffer_info = {}
+  let g:ale_history_log_output = 0
   unlet! g:ale_testft_testlinter1_foo
   unlet! g:ale_testft_testlinter1_bar
   unlet! g:ale_testft2_testlinter2_foo
@@ -218,3 +219,66 @@ Execute (ALEInfo command history should print exit codes correctly):
   \   '(finished - exit code 1) [''/bin/bash'', ''\c'', ''last command'']',
   \ ], "\n"),
   \ g:output
+
+Given testft.testft2 (Empty buffer with two filetypes):
+Execute (ALEInfo command history should print command output if logging is on):
+  let g:ale_history_log_output = 1
+
+  let g:ale_buffer_info[bufnr('%')] = {
+  \ 'history': [
+  \   {
+  \     'status': 'finished',
+  \     'exit_code': 0,
+  \     'job_id': 347,
+  \     'command': 'first command',
+  \     'output': ['some', 'first command output'],
+  \   },
+  \   {
+  \     'status': 'finished',
+  \     'exit_code': 1,
+  \     'job_id': 347,
+  \     'command': ['/bin/bash', '\c', 'last command'],
+  \     'output': ['different second command output'],
+  \   },
+  \   {
+  \     'status': 'finished',
+  \     'exit_code': 0,
+  \     'job_id': 347,
+  \     'command': 'command with no output',
+  \     'output': [],
+  \   },
+  \ ],
+  \}
+
+  call ale#linter#Define('testft', g:testlinter1)
+  call ale#linter#Define('testft2', g:testlinter2)
+  redir => g:output
+  silent ALEInfo
+  redir END
+  AssertEqual
+  \ join([
+  \   '',
+  \   ' Current Filetype: testft.testft2',
+  \   'Available Linters: [''testlinter1'', ''testlinter2'']',
+  \   '  Enabled Linters: [''testlinter1'', ''testlinter2'']',
+  \   ' Linter Variables:',
+  \   g:globals_string . g:command_header,
+  \   '(finished - exit code 0) ''first command''',
+  \   '',
+  \   '<<<OUTPUT STARTS>>>',
+  \   'some',
+  \   'first command output',
+  \   '<<<OUTPUT ENDS>>>',
+  \   '',
+  \   '(finished - exit code 1) [''/bin/bash'', ''\c'', ''last command'']',
+  \   '',
+  \   '<<<OUTPUT STARTS>>>',
+  \   'different second command output',
+  \   '<<<OUTPUT ENDS>>>',
+  \   '',
+  \   '(finished - exit code 0) ''command with no output''',
+  \   '',
+  \   '<<<NO OUTPUT RETURNED>>>',
+  \   '',
+  \ ], "\n"),
+  \ g:output