cmd/gerritbot: constrain posts on common mistakes to development branches

This change is intended to avoid reporting suggestions that are
intended for development branches, like:

The commit title should start with the primary affected package
name followed by a colon, like "net/http: improve [...]"

On backport CLs on release and internal branches, such as:

"[release-branch.go1.22] os/exec: on Windows look for [...]"

Since their possible mistakes don't quite follow the same rules.

For golang/go#61573.

Change-Id: I36c2317a999768eb9cfce6412278d0ed1c82da72
GitHub-Last-Rev: d4f6ba3
GitHub-Pull-Request: #97
Reviewed-on: https://go-review.googlesource.com/c/build/+/591455
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Michael Pratt <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: qiulaidongfeng

cmd/gerritbot/gerritbot.go

@@ -789,7 +789,15 @@ Please visit Gerrit at %s.
 		return err
 	}
 
-	if newCL {
+	checkCommonMistakes := newCL
+	if releaseOrInternalBranch := strings.HasPrefix(pr.Base.GetRef(), "release-branch.") ||
+		strings.HasPrefix(pr.Base.GetRef(), "internal-branch."); releaseOrInternalBranch {
+		// The rules for commit messages on release and internal branches
+		// are different, so don't use the same rules for checking for
+		// common mistakes.
+		checkCommonMistakes = false
+	}
+	if checkCommonMistakes {
 		// Check if we spot any problems with the CL according to our internal
 		// set of rules, and if so, add an unresolved comment to Gerrit.
 		// If the author responds to this, it also helps a reviewer see the author has