run-tests: add support for marking tests as very slow I want to add tests for our packaging rules, but those necessarily run a whole build, or possibly two if both native packaging and docker are available. This lets us flag such tests with a `#require slow` so that they don't unnecessarily slow down normal test runs.

--- a/tests/hghave.py
+++ b/tests/hghave.py
@@ -427,3 +427,7 @@
 @check("pure", "running with pure Python code")
 def has_pure():
     return os.environ.get("HGTEST_RUN_TESTS_PURE") == "--pure"
+
+@check("slow", "allow slow tests")
+def has_slow():
+    return os.environ.get('HGTEST_SLOW') == 'slow'