Bug 1753701: Always default to `--outgoing`/`--workdir` in `./mach lint` r=ahal

Tweaks `./mach lint` behaviour to always fall back to only linting files
that have changed according to VCS - previously, this only happened if
no linter was provided.

Adjusts "am I at $topsrcdir" check to use `pathlib` to avoid mismatches
due to inconsistent capitalization or slash direction.

Updates CI references to explicitly provide `*` as the path to avoid
the only-lint-files-changed restriction.

Differential Revision: https://phabricator.services.mozilla.com/D137870

python/mozlint/mozlint/cli.py

@@ -5,6 +5,7 @@
 import os
 import sys
 from argparse import REMAINDER, SUPPRESS, ArgumentParser
+from pathlib import Path
 
 from mozlint.errors import NoValidLinter
 from mozlint.formatters import all_formatters
@@ -360,12 +361,7 @@ def run(
                 return 1
             paths = lint.linters[0]["local_exclude"]
 
-        if (
-            not linters
-            and not paths
-            and os.getcwd() == lint.root
-            and not (outgoing or workdir)
-        ):
+        if not paths and Path.cwd() == Path(lint.root) and not (outgoing or workdir):
             print(
                 "warning: linting the entire repo takes a long time, using --outgoing and "
                 "--workdir instead. If you want to lint the entire repo, run `./mach lint .`"

taskcluster/ci/source-test/mozlint.yml

@@ -105,7 +105,7 @@ eslint:
             cp -r /build/node_modules_eslint node_modules &&
             ln -s ../tools/lint/eslint/eslint-plugin-mozilla node_modules &&
             ln -s ../tools/lint/eslint/eslint-plugin-spidermonkey-js node_modules &&
-            ./mach lint -v -l eslint -f treeherder -f json:/builds/worker/mozlint.json
+            ./mach lint -v -l eslint -f treeherder -f json:/builds/worker/mozlint.json *
     when:
         files-changed:
             # Files that are likely audited.
@@ -482,7 +482,7 @@ fluent-lint:
     treeherder:
         symbol: l10n(fluent)
     run:
-        mach: lint --linter fluent-lint -f treeherder -f json:/builds/worker/mozlint.json
+        mach: lint --linter fluent-lint -f treeherder -f json:/builds/worker/mozlint.json *
     when:
         files-changed:
             - '**/*.ftl'