Use full-file highlighting for diff sections (#36561)

* Fix #35252
* Fix #35999
* Improve diff rendering, don't add unnecessary "added"/"removed" tags for a full-line change
* Also fix a "space trimming" bug in #36539 and add tests
* Use chroma "SQL" lexer instead of "MySQL" to workaround a bug (35999)

services/repository/files/temp_repo.go

@@ -361,7 +361,7 @@ func (t *TemporaryUploadRepository) Push(ctx context.Context, doer *user_model.U
 }
 
 // DiffIndex returns a Diff of the current index to the head
-func (t *TemporaryUploadRepository) DiffIndex(ctx context.Context) (*gitdiff.Diff, error) {
+func (t *TemporaryUploadRepository) DiffIndex(ctx context.Context, oldContent, newContent string) (*gitdiff.Diff, error) {
 	var diff *gitdiff.Diff
 	cmd := gitcmd.NewCommand("diff-index", "--src-prefix=\\a/", "--dst-prefix=\\b/", "--cached", "-p", "HEAD")
 	stdoutReader, stdoutReaderClose := cmd.MakeStdoutPipe()
@@ -383,6 +383,9 @@ func (t *TemporaryUploadRepository) DiffIndex(ctx context.Context) (*gitdiff.Dif
 		return nil, fmt.Errorf("unable to run diff-index pipeline in temporary repo: %w", err)
 	}
 
+	if len(diff.Files) > 0 {
+		gitdiff.FillDiffFileHighlightLinesByContent(diff.Files[0], util.UnsafeStringToBytes(oldContent), util.UnsafeStringToBytes(newContent))
+	}
 	return diff, nil
 }