Bug 1834590 - [stylelint] Use "stylelint-rc" from stylelint.yml if it exists....

Bug 1834590 - [stylelint] Use "stylelint-rc" from stylelint.yml if it exists. r=linter-reviewers,Standard8

Default to using .stylelintrc.js in $topsrcdir with optional override for
Thunderbird's config file in comm-central.

Differential Revision: https://phabricator.services.mozilla.com/D178835

tools/lint/stylelint/__init__.py

@@ -78,6 +78,9 @@ def lint(paths, config, binary=None, fix=None, rules=[], setup=None, **lintargs)
             ["--ignore-pattern", os.path.relpath(path, lintargs["root"])]
         )
 
+    # Default to $topsrcdir/.stylelintrc.js, but allow override in stylelint.yml
+    stylelint_rc = config.get("stylelint-rc", ".stylelintrc.js")
+
     # First run Stylelint
     cmd_args = (
         [
@@ -89,7 +92,7 @@ def lint(paths, config, binary=None, fix=None, rules=[], setup=None, **lintargs)
             "json",
             "--allow-empty-input",
             "--config",
-            os.path.join(lintargs["root"], ".stylelintrc.js"),
+            os.path.join(lintargs["root"], stylelint_rc),
         ]
         + extra_args
         + exclude_args