chore: migrate mail themes to shared framework and locked upstream inputs

tools/upstream/cache_test.go

@@ -0,0 +1,53 @@
+package upstream
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestPrepareCacheIsPinnedAndReusableOffline(t *testing.T) {
+	s, err := LoadPinned(filepath.Join("..", ".."))
+	if err != nil {
+		t.Fatal(err)
+	}
+	root := t.TempDir()
+	b, _ := json.Marshal(s.Lock)
+	if err = os.WriteFile(filepath.Join(root, "gitea.lock.json"), b, 0644); err != nil {
+		t.Fatal(err)
+	}
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		prefix := "/" + s.Lock.Commit + "/"
+		if !strings.HasPrefix(r.URL.Path, prefix) {
+			t.Errorf("unpinned request %s", r.URL.Path)
+			http.NotFound(w, r)
+			return
+		}
+		data, ok := s.Files[strings.TrimPrefix(r.URL.Path, prefix)]
+		if !ok {
+			http.NotFound(w, r)
+			return
+		}
+		w.Write(data)
+	}))
+	if _, err := prepareFrom(context.Background(), root, server.URL+"/"); err != nil {
+		server.Close()
+		t.Fatal(err)
+	}
+	server.Close()
+	if _, err := prepareFrom(context.Background(), root, server.URL+"/"); err != nil {
+		t.Fatalf("offline cache: %v", err)
+	}
+	path := filepath.Join(CacheDir(root), "templates", "mail", "base", "head.tmpl")
+	if err = os.WriteFile(path, []byte("corrupt"), 0644); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := prepareFrom(context.Background(), root, server.URL+"/"); err == nil {
+		t.Fatal("corrupt cache was accepted")
+	}
+}