fix: add support the http HEAD request method for generic packages (#12865)

Closes #6871

### Tests for Go changes

- I added test coverage for Go changes...
  - [ ] in their respective `*_test.go` for unit tests.
  - [x] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I ran...
  - [x] `make pr-go` before pushing

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.

### Release notes

- [x] This change will be noticed by a Forgejo user or admin (feature, bug fix, performance, etc.). I suggest to include a release note for this change.
- [ ] This change is not visible to a Forgejo user or admin (refactor, dependency upgrade, etc.). I think there is no need to add a release note for this change.

<!--start release-notes-assistant-->

## Release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- Bug fixes
  - [PR](https://codeberg.org/forgejo/forgejo/pulls/12865): <!--number 12865 --><!--line 0 --><!--description YWRkIHN1cHBvcnQgdGhlIGh0dHAgSEVBRCByZXF1ZXN0IG1ldGhvZCBmb3IgZ2VuZXJpYyBwYWNrYWdlcw==-->add support the http HEAD request method for generic packages<!--description-->
<!--end release-notes-assistant-->

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12865
Reviewed-by: Gusted <gusted@noreply.codeberg.org>

routers/api/packages/api.go

@@ -505,6 +505,7 @@ func CommonRoutes() *web.Route {
 			r.Group("/{packagename}/{packageversion}", func() {
 				r.Delete("", reqPackageAccess(perm.AccessModeWrite), generic.DeletePackage)
 				r.Group("/{filename}", func() {
+					r.Head("", generic.CheckPackageFileExistence)
 					r.Get("", generic.DownloadPackageFile)
 					r.Group("", func() {
 						r.Put("", enforcePackagesQuota(), generic.UploadPackage)

routers/api/packages/generic/generic.go

@@ -29,6 +29,38 @@ func apiError(ctx *context.Context, status int, obj any) {
 	})
 }
 
+func CheckPackageFileExistence(ctx *context.Context) {
+	pv, err := packages_model.GetVersionByNameAndVersion(
+		ctx,
+		ctx.Package.Owner.ID,
+		packages_model.TypeGeneric,
+		ctx.Params("packagename"),
+		ctx.Params("packageversion"),
+	)
+	if err != nil {
+		if err == packages_model.ErrPackageNotExist {
+			apiError(ctx, http.StatusNotFound, err)
+			return
+		}
+		apiError(ctx, http.StatusInternalServerError, err)
+	}
+
+	pf, err := packages_model.GetFileForVersionByName(ctx, pv.ID, ctx.Params("filename"), "")
+	if err != nil {
+		if err == packages_model.ErrPackageFileNotExist {
+			apiError(ctx, http.StatusNotFound, err)
+			return
+		}
+		apiError(ctx, http.StatusInternalServerError, err)
+	}
+
+	ctx.SetServeHeaders(&context.ServeHeaderOptions{
+		Filename:     pf.Name,
+		LastModified: pf.CreatedUnix.AsLocalTime(),
+	})
+	ctx.Status(http.StatusOK)
+}
+
 // DownloadPackageFile serves the specific generic package.
 func DownloadPackageFile(ctx *context.Context) {
 	s, u, pf, err := packages_service.GetFileStreamByPackageNameAndVersion(

tests/integration/api_packages_generic_test.go

@@ -116,7 +116,10 @@ func TestPackageGeneric(t *testing.T) {
 
 		checkDownloadCount(0)
 
-		req := NewRequest(t, "GET", url+"/"+filename)
+		req := NewRequest(t, "HEAD", url+"/"+filename)
+		MakeRequest(t, req, http.StatusOK)
+
+		req = NewRequest(t, "GET", url+"/"+filename)
 		resp := MakeRequest(t, req, http.StatusOK)
 
 		assert.Equal(t, content, resp.Body.Bytes())
@@ -131,7 +134,10 @@ func TestPackageGeneric(t *testing.T) {
 		t.Run("NotExists", func(t *testing.T) {
 			defer tests.PrintCurrentTest(t)()
 
-			req := NewRequest(t, "GET", url+"/not.found")
+			req := NewRequest(t, "HEAD", url+"/not.found")
+			MakeRequest(t, req, http.StatusNotFound)
+
+			req = NewRequest(t, "GET", url+"/not.found")
 			MakeRequest(t, req, http.StatusNotFound)
 		})
 
@@ -143,6 +149,9 @@ func TestPackageGeneric(t *testing.T) {
 				setting.Service.RequireSignInView = false
 			}()
 
+			req = NewRequest(t, "HEAD", url+"/dummy.bin")
+			MakeRequest(t, req, http.StatusUnauthorized)
+
 			req = NewRequest(t, "GET", url+"/dummy.bin")
 			MakeRequest(t, req, http.StatusUnauthorized)
 		})
@@ -164,7 +173,10 @@ func TestPackageGeneric(t *testing.T) {
 				setting.Packages.Storage.MinioConfig.ServeDirect = true
 			}
 
-			req := NewRequest(t, "GET", url+"/"+filename)
+			req := NewRequest(t, "HEAD", url+"/"+filename)
+			MakeRequest(t, req, http.StatusOK)
+
+			req = NewRequest(t, "GET", url+"/"+filename)
 			resp := MakeRequest(t, req, http.StatusSeeOther)
 
 			checkDownloadCount(3)