Fix #410 - Use compile_commands.json files for clang-tidy, and check files on disk instead

test/command_callback/test_clang_tidy_command_callback.vader

@@ -0,0 +1,31 @@
+Before:
+  Save g:ale_cpp_clangtidy_checks
+  Save g:ale_cpp_clangtidy_options
+  runtime ale_linters/cpp/clangtidy.vim
+
+After:
+  Restore
+  call ale#linter#Reset()
+
+Execute(The clangtidy command default should be correct):
+  AssertEqual
+  \ 'clang-tidy -checks=''*'' %s',
+  \ ale_linters#cpp#clangtidy#GetCommand(bufnr(''))
+
+Execute(You should be able to remove the -checks option for clang-tidy):
+  let g:ale_cpp_clangtidy_checks = []
+  AssertEqual
+  \ 'clang-tidy %s',
+  \ ale_linters#cpp#clangtidy#GetCommand(bufnr(''))
+
+Execute(You should be able to set other checks for clang-tidy):
+  let g:ale_cpp_clangtidy_checks = ['-*', 'clang-analyzer-*']
+  AssertEqual
+  \ 'clang-tidy -checks=''-*,clang-analyzer-*'' %s',
+  \ ale_linters#cpp#clangtidy#GetCommand(bufnr(''))
+
+Execute(You should be able to manually set compiler flags for clang-tidy):
+  let g:ale_cpp_clangtidy_options = '-Wall'
+  AssertEqual
+  \ 'clang-tidy -checks=''*'' %s -- -Wall',
+  \ ale_linters#cpp#clangtidy#GetCommand(bufnr(''))