Closes #18164: on pre-push, check for uncommitted glean docs.

config/pre-push-recommended.sh

@@ -14,6 +14,25 @@
 # Descriptions for each gradle task below can be found in the
 # output of `./gradlew tasks`.
 
+# Prevent push if generated glean docs are not committed.
+# A better implementation would make sure these doc updates
+# only came from this commit.
+./gradlew -q \
+        gleanGenerateMetricsDocsForDebug \
+        gleanGenerateMetricsSourceForDebug
+if git status --porcelain=v1 | grep -q "docs/metrics.md"; then
+  echo "
+FAIL pre-push hook: generated glean file, docs/metrics.md, has uncommitted changes.
+Please commit these files and try again.
+
+This check tries to prevent these generated files from being uncommitted on master.
+However, it may fail unintuitively if we're in that state. If this happens often
+and is disruptive to your workflow, please notify mcomella so we can improve this
+check." >&2
+  exit 1
+fi
+
+# Run core checks.
 ./gradlew -q \
         ktlint \
         detekt \