2 files changed, 14 insertions, 3 deletions

diff --git a/src/ci/docker/x86_64-gnu-tools/checkregression.py b/src/ci/docker/x86_64-gnu-tools/checkregression.py
index 72acb107405..4fbb8c4d203 100755
--- a/src/ci/docker/x86_64-gnu-tools/checkregression.py
+++ b/src/ci/docker/x86_64-gnu-tools/checkregression.py
@@ -1,10 +1,16 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
+## This script has two purposes: detect any tool that *regressed*, which is used
+## during the week before the beta branches to reject PRs; and detect any tool
+## that *changed* to see if we need to update the toolstate repo.
+
 import sys
 import json
 
-# Regressions for these tools do not cause failure.
+# Regressions for these tools during the beta cutoff week do not cause failure.
+# See `status_check` in `checktools.sh` for tools that have to pass on the
+# beta/stable branches.
 REGRESSION_OK = ["rustc-guide", "miri", "embedded-book"]
 
 if __name__ == '__main__':
diff --git a/src/ci/docker/x86_64-gnu-tools/checktools.sh b/src/ci/docker/x86_64-gnu-tools/checktools.sh
index 8df63c214e1..db10c84a997 100755
--- a/src/ci/docker/x86_64-gnu-tools/checktools.sh
+++ b/src/ci/docker/x86_64-gnu-tools/checktools.sh
@@ -79,6 +79,9 @@ check_dispatch() {
 # List all tools here.
 # This function gets called with "submodule_changed" for each PR that changed a submodule,
 # and with "beta_required" for each PR that lands on beta/stable.
+# The purpose of this function is to *reject* PRs if a tool is not "test-pass" and
+# (a) the tool's submodule has been updated, or (b) we landed on beta/stable and the
+# tool has to "test-pass" on that branch.
 status_check() {
     check_dispatch $1 beta book src/doc/book
     check_dispatch $1 beta nomicon src/doc/nomicon
@@ -88,8 +91,10 @@ status_check() {
     check_dispatch $1 beta rls src/tools/rls
     check_dispatch $1 beta rustfmt src/tools/rustfmt
     check_dispatch $1 beta clippy-driver src/tools/clippy
-    # These tools are not required on the beta/stable branches.
-    # They will still cause failure during the beta cutoff week, see `checkregression.py` for that.
+    # These tools are not required on the beta/stable branches, but they *do* cause
+    # PRs to fail if a submodule update does not fix them.
+    # They will still cause failure during the beta cutoff week, unless `checkregression.py`
+    # exempts them from that.
     check_dispatch $1 nightly miri src/tools/miri
     check_dispatch $1 nightly embedded-book src/doc/embedded-book
 }