Delete vendor/ and the route proxy's: the build module fetches the modules, the root image builds with -mod=mod (issue 1305, C6)

internal/lint/removed_test.go

@@ -20,3 +20,24 @@ func TestTheRepositoryHoldsNoMergeCheckScript(t *testing.T) {
 		}
 	}
 }
+
+// No module of this repository keeps a copy of its dependencies (issue 1305): the build module fetches them, and
+// `go build ./...` with GOFLAGS=-mod=mod is how every build reads them.
+func TestTheRepositoryHoldsNoVendorDirectory(t *testing.T) {
+	err := filepath.WalkDir(root, func(path string, d os.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() && d.Name() == ".git" {
+			return filepath.SkipDir
+		}
+		if d.IsDir() && d.Name() == "vendor" {
+			t.Errorf("%s is a vendor directory: dependencies are fetched, never kept (issue 1305)", path)
+			return filepath.SkipDir
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}