godoc/redirect: update the rules for /cl/ redirect

If id is a number greater than 150k, then it is a Rietveld CL, otherwise
treat it as a Gerrit change id.

Also add support for /cl/ID/, because go commit 0edafefc36 uses this
form.

Change-Id: I46575e3284faaa727e346b34bbc46ab248cf12b3
Signed-off-by: Shenghou Ma <[email protected]>
Reviewed-on: https://go-review.googlesource.com/1283
Reviewed-by: Andrew Gerrand <[email protected]>

Author: minux

godoc/redirect/redirect.go

@@ -177,17 +177,19 @@ func clHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	id := r.URL.Path[len(prefix):]
+	// support /cl/152700045/, which is used in commit 0edafefc36.
+	id = strings.TrimSuffix(id, "/")
 	if !validId.MatchString(id) {
 		http.Error(w, "Not found", http.StatusNotFound)
 		return
 	}
 	target := ""
-	// the first CL in rietveld is about 152046, so if id is less than
-	// 150000, treat it as a Gerrit change id.
-	if n, _ := strconv.Atoi(id); strings.HasPrefix(id, "I") || n < 150000 {
-		target = "https://go-review.googlesource.com/#/q/" + id
-	} else {
+	// the first CL in rietveld is about 152046, so only treat the id as
+	// a rietveld CL if it is larger than 150000.
+	if n, err := strconv.Atoi(id); err == nil && n > 150000 {
 		target = "https://codereview.appspot.com/" + id
+	} else {
+		target = "https://go-review.googlesource.com/r/" + id
 	}
 	http.Redirect(w, r, target, http.StatusFound)
 }