Update PR template to include the "Fixes commit" message when reverting or fixing bad commits (envoyproxy#18298)

Signed-off-by: Yan Avlasov <[email protected]>

Author: yanavlasov

PULL_REQUESTS.md

@@ -102,6 +102,19 @@ you may instead just tag the PR with the issue:
 
 \#Issue
 
+### <a name="commit"></a>Commit
+
+If this PR fixes or reverts a buggy commit, please add a line of the form:
+
+Fixes commit #PR
+
+or
+
+Fixes commit SHA
+
+This will allow automated tools to detect tainted commit ranges on the main branch when the PR is
+merged.
+
 ### <a name="deprecated"></a>Deprecated
 
 If this PR deprecates existing Envoy APIs or code, it should include an update to the deprecated

PULL_REQUEST_TEMPLATE.md

@@ -21,5 +21,6 @@ Release Notes:
 Platform Specific Features:
 [Optional Runtime guard:]
 [Optional Fixes #Issue]
+[Optional Fixes commit #PR or SHA]
 [Optional Deprecated:]
 [Optional [API Considerations](https://github.com/envoyproxy/envoy/blob/main/api/review_checklist.md):]