Fix LFS file not stored in LFS when uploaded/edited via API or web UI (#34367)

Files that should be stored in LFS and are uploaded/edited from the API
or web UI aren't stored in LFS. This may be a regression from #34154.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

3 files changed, 24 insertions, 2 deletions

diff --git a/modules/git/attribute/checker.go b/modules/git/attribute/checker.go
index c17006a154..167b31416e 100644
--- a/modules/git/attribute/checker.go
+++ b/modules/git/attribute/checker.go
@@ -39,7 +39,12 @@ func checkAttrCommand(gitRepo *git.Repository, treeish string, filenames, attrib
 			)
 			cancel = deleteTemporaryFile
 		}
-	} // else: no treeish, assume it is a not a bare repo, read from working directory
+	} else {
+		// Read from existing index, in cases where the repo is bare and has an index,
+		// or the work tree contains unstaged changes that shouldn't affect the attribute check.
+		// It is caller's responsibility to add changed ".gitattributes" into the index if they want to respect the new changes.
+		cmd.AddArguments("--cached")
+	}
 
 	cmd.AddDynamicArguments(attributes...)
 	if len(filenames) > 0 {
diff --git a/modules/git/attribute/checker_test.go b/modules/git/attribute/checker_test.go
index 97db43460b..67fbda8918 100644
--- a/modules/git/attribute/checker_test.go
+++ b/modules/git/attribute/checker_test.go
@@ -57,8 +57,18 @@ func Test_Checker(t *testing.T) {
 		assert.Equal(t, expectedAttrs(), attrs["i-am-a-python.p"])
 	})
 
+	t.Run("Run git check-attr in bare repository using index", func(t *testing.T) {
+		attrs, err := CheckAttributes(t.Context(), gitRepo, "", CheckAttributeOpts{
+			Filenames:  []string{"i-am-a-python.p"},
+			Attributes: LinguistAttributes,
+		})
+		assert.NoError(t, err)
+		assert.Len(t, attrs, 1)
+		assert.Equal(t, expectedAttrs(), attrs["i-am-a-python.p"])
+	})
+
 	if !git.DefaultFeatures().SupportCheckAttrOnBare {
-		t.Skip("git version 2.40 is required to support run check-attr on bare repo")
+		t.Skip("git version 2.40 is required to support run check-attr on bare repo without using index")
 		return
 	}
 
diff --git a/services/repository/files/upload.go b/services/repository/files/upload.go
index f348cb68ab..68a071cd28 100644
--- a/services/repository/files/upload.go
+++ b/services/repository/files/upload.go
@@ -107,6 +107,7 @@ func UploadRepoFiles(ctx context.Context, repo *repo_model.Repository, doer *use
 	}
 
 	var attributesMap map[string]*attribute.Attributes
+	// when uploading to an empty repo, the old branch doesn't exist, but some "global gitattributes" or "info/attributes" may exist
 	if setting.LFS.StartServer {
 		attributesMap, err = attribute.CheckAttributes(ctx, t.gitRepo, "" /* use temp repo's working dir */, attribute.CheckAttributeOpts{
 			Attributes: []string{attribute.Filter},
@@ -118,6 +119,12 @@ func UploadRepoFiles(ctx context.Context, repo *repo_model.Repository, doer *use
 	}
 
 	// Copy uploaded files into repository.
+	// TODO: there is a small problem: when uploading LFS files with ".gitattributes", the "check-attr" runs before this loop,
+	// so LFS files are not able to be added as LFS objects. Ideally we need to do in 3 steps in the future:
+	// 1. Add ".gitattributes" to git index
+	// 2. Run "check-attr" (the previous attribute.CheckAttributes call)
+	// 3. Add files to git index (this loop)
+	// This problem is trivial so maybe no need to spend too much time on it at the moment.
 	for i := range infos {
 		if err := copyUploadedLFSFileIntoRepository(ctx, &infos[i], attributesMap, t, opts.TreePath); err != nil {
 			return err