fix: full file highlighting for git diff with CR char (#38484)

fix #38481

services/gitdiff/gitdiff.go

@@ -1285,6 +1285,8 @@ func getDiffBasic(ctx context.Context, gitRepo *git.Repository, opts *DiffOption
 		return nil, nil, nil, err
 	}
 
+	// HINT: GIT-DIFF-HIGHLIGHT-LINE-NUMBER: git doesn't treat CR(\r) as EOL, CR is just a plain char which can appear anywhere in the diff output
+	// Since we have to do full-file-highlighting for the diff result, we need to make sure the highlighted lines exactly match the git's diff output.
 	cmdDiff := gitcmd.NewCommand().
 		AddArguments("diff", "--src-prefix=\\a/", "--dst-prefix=\\b/").
 		AddArguments(opts.WhitespaceBehavior...).
@@ -1405,8 +1407,12 @@ func highlightCodeLines(name, lang string, sections []*DiffSection, isLeft bool,
 	if setting.Git.DisableDiffHighlight || len(rawContent) > MaxFullFileHighlightSizeLimit {
 		return nil
 	}
-
 	content := util.UnsafeBytesToString(charset.ToUTF8(rawContent, charset.ConvertOpts{}))
+	// HINT: GIT-DIFF-HIGHLIGHT-LINE-NUMBER: it should handle all CR(\r) before highlight to make line numbers match
+	if strings.Contains(content, "\r") {
+		content = strings.ReplaceAll(content, "\r\n", "\n")
+		content = strings.ReplaceAll(content, "\r", "␍")
+	}
 	lexer := highlight.DetectChromaLexerByFileName(name, lang)
 	highlightedNewContent := highlight.RenderCodeByLexer(lexer, content)
 	unsafeLines := highlight.UnsafeSplitHighlightedLines(highlightedNewContent)

services/gitdiff/gitdiff_test.go

@@ -1143,6 +1143,19 @@ func TestHighlightCodeLines(t *testing.T) {
 			1: `<span class="n">b</span>` + nl,
 		}, ret)
 	})
+	t.Run("CharCR", func(t *testing.T) {
+		diffFile := &DiffFile{
+			Name: "a.txt",
+			Sections: []*DiffSection{
+				{
+					Lines: []*DiffLine{{LeftIdx: 1}, {LeftIdx: 2}},
+				},
+			},
+		}
+		ret := highlightCodeLinesForDiffFile(diffFile, true, []byte("a\rb\r\nc"))
+		assert.Equal(t, "a␍b\n", string(ret[0]))
+		assert.Equal(t, `c`, string(ret[1]))
+	})
 }
 
 func TestSyncUserSpecificDiff_UpdatedFiles(t *testing.T) {