Add .gitattribute assisted language detection to blame, diff and render (#17590)

Use check attribute code to check the assigned language of a file and send that in to
chroma as a hint for the language of the file.

Signed-off-by: Andrew Thornton <art27@cantab.net>

13 files changed, 221 insertions, 95 deletions

diff --git a/docs/content/doc/advanced/config-cheat-sheet.en-us.md b/docs/content/doc/advanced/config-cheat-sheet.en-us.md
index 3b5d9213df..a087b253e9 100644
--- a/docs/content/doc/advanced/config-cheat-sheet.en-us.md
+++ b/docs/content/doc/advanced/config-cheat-sheet.en-us.md
@@ -982,6 +982,14 @@ Multiple sanitisation rules can be defined by adding unique subsections, e.g. `[
 To apply a sanitisation rules only for a specify external renderer they must use the renderer name, e.g. `[markup.sanitizer.asciidoc.rule-1]`.
 If the rule is defined above the renderer ini section or the name does not match a renderer it is applied to every renderer.
 
+## Highlight Mappings (`highlight.mapping`)
+
+- `file_extension e.g. .toml`: **language e.g. ini**. File extension to language mapping overrides.
+
+- Gitea will highlight files using the `linguist-language` or `gitlab-language` attribute from the `.gitattributes` file
+if available. If this is not set or the language is unavailable, the file extension will be looked up
+in this mapping or the filetype using heuristics.
+
 ## Time (`time`)
 
 - `FORMAT`: Time format to display on UI. i.e. RFC1123 or 2006-01-02 15:04:05
diff --git a/modules/git/repo_attribute.go b/modules/git/repo_attribute.go
index aace644253..88fb7810a6 100644
--- a/modules/git/repo_attribute.go
+++ b/modules/git/repo_attribute.go
@@ -22,6 +22,8 @@ type CheckAttributeOpts struct {
 	AllAttributes bool
 	Attributes    []string
 	Filenames     []string
+	IndexFile     string
+	WorkTree      string
 }
 
 // CheckAttribute return the Blame object of file
@@ -31,6 +33,19 @@ func (repo *Repository) CheckAttribute(opts CheckAttributeOpts) (map[string]map[
 		return nil, fmt.Errorf("git version missing: %v", err)
 	}
 
+	env := []string{}
+
+	if len(opts.IndexFile) > 0 && CheckGitVersionAtLeast("1.7.8") == nil {
+		env = append(env, "GIT_INDEX_FILE="+opts.IndexFile)
+	}
+	if len(opts.WorkTree) > 0 && CheckGitVersionAtLeast("1.7.8") == nil {
+		env = append(env, "GIT_WORK_TREE="+opts.WorkTree)
+	}
+
+	if len(env) > 0 {
+		env = append(os.Environ(), env...)
+	}
+
 	stdOut := new(bytes.Buffer)
 	stdErr := new(bytes.Buffer)
 
@@ -61,7 +76,7 @@ func (repo *Repository) CheckAttribute(opts CheckAttributeOpts) (map[string]map[
 
 	cmd := NewCommand(cmdArgs...)
 
-	if err := cmd.RunInDirPipeline(repo.Path, stdOut, stdErr); err != nil {
+	if err := cmd.RunInDirTimeoutEnvPipeline(env, -1, repo.Path, stdOut, stdErr); err != nil {
 		return nil, fmt.Errorf("failed to run check-attr: %v\n%s\n%s", err, stdOut.String(), stdErr.String())
 	}
 
diff --git a/modules/git/repo_index.go b/modules/git/repo_index.go
index 27cb7fbebe..38c01295b6 100644
--- a/modules/git/repo_index.go
+++ b/modules/git/repo_index.go
@@ -8,6 +8,7 @@ import (
 	"bytes"
 	"context"
 	"os"
+	"path/filepath"
 	"strings"
 
 	"code.gitea.io/gitea/modules/log"
@@ -45,14 +46,15 @@ func (repo *Repository) readTreeToIndex(id SHA1, indexFilename ...string) error
 }
 
 // ReadTreeToTemporaryIndex reads a treeish to a temporary index file
-func (repo *Repository) ReadTreeToTemporaryIndex(treeish string) (filename string, cancel context.CancelFunc, err error) {
-	tmpIndex, err := os.CreateTemp("", "index")
+func (repo *Repository) ReadTreeToTemporaryIndex(treeish string) (filename, tmpDir string, cancel context.CancelFunc, err error) {
+	tmpDir, err = os.MkdirTemp("", "index")
 	if err != nil {
 		return
 	}
-	filename = tmpIndex.Name()
+
+	filename = filepath.Join(tmpDir, ".tmp-index")
 	cancel = func() {
-		err := util.Remove(filename)
+		err := util.RemoveAll(tmpDir)
 		if err != nil {
 			log.Error("failed to remove tmp index file: %v", err)
 		}
@@ -60,7 +62,7 @@ func (repo *Repository) ReadTreeToTemporaryIndex(treeish string) (filename strin
 	err = repo.ReadTreeToIndex(treeish, filename)
 	if err != nil {
 		defer cancel()
-		return "", func() {}, err
+		return "", "", func() {}, err
 	}
 	return
 }
diff --git a/modules/git/repo_language_stats_gogit.go b/modules/git/repo_language_stats_gogit.go
index d37827c3de..037ec41ec6 100644
--- a/modules/git/repo_language_stats_gogit.go
+++ b/modules/git/repo_language_stats_gogit.go
@@ -11,11 +11,10 @@ import (
 	"bytes"
 	"context"
 	"io"
-	"os"
+	"strings"
 
 	"code.gitea.io/gitea/modules/analyze"
 	"code.gitea.io/gitea/modules/log"
-	"code.gitea.io/gitea/modules/util"
 
 	"github.com/go-enry/go-enry/v2"
 	"github.com/go-git/go-git/v5"
@@ -48,35 +47,28 @@ func (repo *Repository) GetLanguageStats(commitID string) (map[string]int64, err
 	var checker *CheckAttributeReader
 
 	if CheckGitVersionAtLeast("1.7.8") == nil {
-		indexFilename, deleteTemporaryFile, err := repo.ReadTreeToTemporaryIndex(commitID)
+		indexFilename, workTree, deleteTemporaryFile, err := repo.ReadTreeToTemporaryIndex(commitID)
 		if err == nil {
 			defer deleteTemporaryFile()
-			tmpWorkTree, err := os.MkdirTemp("", "empty-work-dir")
-			if err == nil {
-				defer func() {
-					_ = util.RemoveAll(tmpWorkTree)
+			checker = &CheckAttributeReader{
+				Attributes: []string{"linguist-vendored", "linguist-generated", "linguist-language", "gitlab-language"},
+				Repo:       repo,
+				IndexFile:  indexFilename,
+				WorkTree:   workTree,
+			}
+			ctx, cancel := context.WithCancel(DefaultContext)
+			if err := checker.Init(ctx); err != nil {
+				log.Error("Unable to open checker for %s. Error: %v", commitID, err)
+			} else {
+				go func() {
+					err = checker.Run()
+					if err != nil {
+						log.Error("Unable to open checker for %s. Error: %v", commitID, err)
+						cancel()
+					}
 				}()
-
-				checker = &CheckAttributeReader{
-					Attributes: []string{"linguist-vendored", "linguist-generated", "linguist-language"},
-					Repo:       repo,
-					IndexFile:  indexFilename,
-					WorkTree:   tmpWorkTree,
-				}
-				ctx, cancel := context.WithCancel(DefaultContext)
-				if err := checker.Init(ctx); err != nil {
-					log.Error("Unable to open checker for %s. Error: %v", commitID, err)
-				} else {
-					go func() {
-						err = checker.Run()
-						if err != nil {
-							log.Error("Unable to open checker for %s. Error: %v", commitID, err)
-							cancel()
-						}
-					}()
-				}
-				defer cancel()
 			}
+			defer cancel()
 		}
 	}
 
@@ -114,6 +106,21 @@ func (repo *Repository) GetLanguageStats(commitID string) (map[string]int64, err
 					sizes[language] += f.Size
 
 					return nil
+				} else if language, has := attrs["gitlab-language"]; has && language != "unspecified" && language != "" {
+					// strip off a ? if present
+					if idx := strings.IndexByte(language, '?'); idx >= 0 {
+						language = language[:idx]
+					}
+					if len(language) != 0 {
+						// group languages, such as Pug -> HTML; SCSS -> CSS
+						group := enry.GetLanguageGroup(language)
+						if len(group) != 0 {
+							language = group
+						}
+
+						sizes[language] += f.Size
+						return nil
+					}
 				}
 			}
 		}
diff --git a/modules/git/repo_language_stats_nogogit.go b/modules/git/repo_language_stats_nogogit.go
index 06269a466c..4fda7ab627 100644
--- a/modules/git/repo_language_stats_nogogit.go
+++ b/modules/git/repo_language_stats_nogogit.go
@@ -13,11 +13,10 @@ import (
 	"context"
 	"io"
 	"math"
-	"os"
+	"strings"
 
 	"code.gitea.io/gitea/modules/analyze"
 	"code.gitea.io/gitea/modules/log"
-	"code.gitea.io/gitea/modules/util"
 
 	"github.com/go-enry/go-enry/v2"
 )
@@ -68,35 +67,28 @@ func (repo *Repository) GetLanguageStats(commitID string) (map[string]int64, err
 	var checker *CheckAttributeReader
 
 	if CheckGitVersionAtLeast("1.7.8") == nil {
-		indexFilename, deleteTemporaryFile, err := repo.ReadTreeToTemporaryIndex(commitID)
+		indexFilename, worktree, deleteTemporaryFile, err := repo.ReadTreeToTemporaryIndex(commitID)
 		if err == nil {
 			defer deleteTemporaryFile()
-			tmpWorkTree, err := os.MkdirTemp("", "empty-work-dir")
-			if err == nil {
-				defer func() {
-					_ = util.RemoveAll(tmpWorkTree)
+			checker = &CheckAttributeReader{
+				Attributes: []string{"linguist-vendored", "linguist-generated", "linguist-language", "gitlab-language"},
+				Repo:       repo,
+				IndexFile:  indexFilename,
+				WorkTree:   worktree,
+			}
+			ctx, cancel := context.WithCancel(DefaultContext)
+			if err := checker.Init(ctx); err != nil {
+				log.Error("Unable to open checker for %s. Error: %v", commitID, err)
+			} else {
+				go func() {
+					err = checker.Run()
+					if err != nil {
+						log.Error("Unable to open checker for %s. Error: %v", commitID, err)
+						cancel()
+					}
 				}()
-
-				checker = &CheckAttributeReader{
-					Attributes: []string{"linguist-vendored", "linguist-generated", "linguist-language"},
-					Repo:       repo,
-					IndexFile:  indexFilename,
-					WorkTree:   tmpWorkTree,
-				}
-				ctx, cancel := context.WithCancel(DefaultContext)
-				if err := checker.Init(ctx); err != nil {
-					log.Error("Unable to open checker for %s. Error: %v", commitID, err)
-				} else {
-					go func() {
-						err = checker.Run()
-						if err != nil {
-							log.Error("Unable to open checker for %s. Error: %v", commitID, err)
-							cancel()
-						}
-					}()
-				}
-				defer cancel()
 			}
+			defer cancel()
 		}
 	}
 
@@ -138,7 +130,23 @@ func (repo *Repository) GetLanguageStats(commitID string) (map[string]int64, err
 
 					sizes[language] += f.Size()
 					continue
+				} else if language, has := attrs["gitlab-language"]; has && language != "unspecified" && language != "" {
+					// strip off a ? if present
+					if idx := strings.IndexByte(language, '?'); idx >= 0 {
+						language = language[:idx]
+					}
+					if len(language) != 0 {
+						// group languages, such as Pug -> HTML; SCSS -> CSS
+						group := enry.GetLanguageGroup(language)
+						if len(group) != 0 {
+							language = group
+						}
+
+						sizes[language] += f.Size()
+						continue
+					}
 				}
+
 			}
 		}
 
diff --git a/modules/highlight/highlight.go b/modules/highlight/highlight.go
index 9a876d2a6b..04bd30bceb 100644
--- a/modules/highlight/highlight.go
+++ b/modules/highlight/highlight.go
@@ -55,7 +55,7 @@ func NewContext() {
 }
 
 // Code returns a HTML version of code string with chroma syntax highlighting classes
-func Code(fileName, code string) string {
+func Code(fileName, language, code string) string {
 	NewContext()
 
 	// diff view newline will be passed as empty, change to literal \n so it can be copied
@@ -69,9 +69,23 @@ func Code(fileName, code string) string {
 	}
 
 	var lexer chroma.Lexer
-	if val, ok := highlightMapping[filepath.Ext(fileName)]; ok {
-		//use mapped value to find lexer
-		lexer = lexers.Get(val)
+
+	if len(language) > 0 {
+		lexer = lexers.Get(language)
+
+		if lexer == nil {
+			// Attempt stripping off the '?'
+			if idx := strings.IndexByte(language, '?'); idx > 0 {
+				lexer = lexers.Get(language[:idx])
+			}
+		}
+	}
+
+	if lexer == nil {
+		if val, ok := highlightMapping[filepath.Ext(fileName)]; ok {
+			//use mapped value to find lexer
+			lexer = lexers.Get(val)
+		}
 	}
 
 	if lexer == nil {
@@ -119,7 +133,7 @@ func CodeFromLexer(lexer chroma.Lexer, code string) string {
 }
 
 // File returns a slice of chroma syntax highlighted lines of code
-func File(numLines int, fileName string, code []byte) []string {
+func File(numLines int, fileName, language string, code []byte) []string {
 	NewContext()
 
 	if len(code) > sizeLimit {
@@ -139,8 +153,16 @@ func File(numLines int, fileName string, code []byte) []string {
 	htmlw := bufio.NewWriter(&htmlbuf)
 
 	var lexer chroma.Lexer
-	if val, ok := highlightMapping[filepath.Ext(fileName)]; ok {
-		lexer = lexers.Get(val)
+
+	// provided language overrides everything
+	if len(language) > 0 {
+		lexer = lexers.Get(language)
+	}
+
+	if lexer == nil {
+		if val, ok := highlightMapping[filepath.Ext(fileName)]; ok {
+			lexer = lexers.Get(val)
+		}
 	}
 
 	if lexer == nil {
diff --git a/modules/highlight/highlight_test.go b/modules/highlight/highlight_test.go
index 29a15c0b53..3f47b6a48f 100644
--- a/modules/highlight/highlight_test.go
+++ b/modules/highlight/highlight_test.go
@@ -96,7 +96,7 @@ steps:
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			if got := File(tt.numLines, tt.fileName, []byte(tt.code)); !reflect.DeepEqual(got, tt.want) {
+			if got := File(tt.numLines, tt.fileName, "", []byte(tt.code)); !reflect.DeepEqual(got, tt.want) {
 				t.Errorf("File() = %v, want %v", got, tt.want)
 			}
 		})
diff --git a/modules/indexer/code/search.go b/modules/indexer/code/search.go
index 51b7c9427d..bb8dcf16b3 100644
--- a/modules/indexer/code/search.go
+++ b/modules/indexer/code/search.go
@@ -101,7 +101,7 @@ func searchResult(result *SearchResult, startIndex, endIndex int) (*Result, erro
 		Language:       result.Language,
 		Color:          result.Color,
 		LineNumbers:    lineNumbers,
-		FormattedLines: highlight.Code(result.Filename, formattedLinesBuffer.String()),
+		FormattedLines: highlight.Code(result.Filename, "", formattedLinesBuffer.String()),
 	}, nil
 }
 
diff --git a/modules/repofiles/diff_test.go b/modules/repofiles/diff_test.go
index 463ce4ec67..4bd1ef6f4d 100644
--- a/modules/repofiles/diff_test.go
+++ b/modules/repofiles/diff_test.go
@@ -9,6 +9,7 @@ import (
 
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/models/unittest"
+	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/test"
 	"code.gitea.io/gitea/services/gitdiff"
 
@@ -118,13 +119,21 @@ func TestGetDiffPreview(t *testing.T) {
 	t.Run("with given branch", func(t *testing.T) {
 		diff, err := GetDiffPreview(ctx.Repo.Repository, branch, treePath, content)
 		assert.NoError(t, err)
-		assert.EqualValues(t, expectedDiff, diff)
+		expectedBs, err := json.Marshal(expectedDiff)
+		assert.NoError(t, err)
+		bs, err := json.Marshal(diff)
+		assert.NoError(t, err)
+		assert.EqualValues(t, expectedBs, bs)
 	})
 
 	t.Run("empty branch, same results", func(t *testing.T) {
 		diff, err := GetDiffPreview(ctx.Repo.Repository, "", treePath, content)
 		assert.NoError(t, err)
-		assert.EqualValues(t, expectedDiff, diff)
+		expectedBs, err := json.Marshal(expectedDiff)
+		assert.NoError(t, err)
+		bs, err := json.Marshal(diff)
+		assert.NoError(t, err)
+		assert.EqualValues(t, expectedBs, bs)
 	})
 }
 
diff --git a/routers/web/repo/blame.go b/routers/web/repo/blame.go
index 110ec037e1..2fd72d81ab 100644
--- a/routers/web/repo/blame.go
+++ b/routers/web/repo/blame.go
@@ -16,6 +16,7 @@ import (
 	"code.gitea.io/gitea/modules/context"
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/highlight"
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/templates"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"
@@ -204,6 +205,31 @@ func processBlameParts(ctx *context.Context, blameParts []git.BlamePart) (map[st
 func renderBlame(ctx *context.Context, blameParts []git.BlamePart, commitNames map[string]*models.UserCommit, previousCommits map[string]string) {
 	repoLink := ctx.Repo.RepoLink
 
+	language := ""
+
+	indexFilename, worktree, deleteTemporaryFile, err := ctx.Repo.GitRepo.ReadTreeToTemporaryIndex(ctx.Repo.CommitID)
+	if err == nil {
+		defer deleteTemporaryFile()
+
+		filename2attribute2info, err := ctx.Repo.GitRepo.CheckAttribute(git.CheckAttributeOpts{
+			CachedOnly: true,
+			Attributes: []string{"linguist-language", "gitlab-language"},
+			Filenames:  []string{ctx.Repo.TreePath},
+			IndexFile:  indexFilename,
+			WorkTree:   worktree,
+		})
+		if err != nil {
+			log.Error("Unable to load attributes for %-v:%s. Error: %v", ctx.Repo.Repository, ctx.Repo.TreePath, err)
+		}
+
+		language = filename2attribute2info[ctx.Repo.TreePath]["linguist-language"]
+		if language == "" || language == "unspecified" {
+			language = filename2attribute2info[ctx.Repo.TreePath]["gitlab-language"]
+		}
+		if language == "unspecified" {
+			language = ""
+		}
+	}
 	var lines = make([]string, 0)
 	rows := make([]*blameRow, 0)
 
@@ -248,7 +274,7 @@ func renderBlame(ctx *context.Context, blameParts []git.BlamePart, commitNames m
 				line += "\n"
 			}
 			fileName := fmt.Sprintf("%v", ctx.Data["FileName"])
-			line = highlight.Code(fileName, line)
+			line = highlight.Code(fileName, language, line)
 
 			br.Code = gotemplate.HTML(line)
 			rows = append(rows, br)
diff --git a/routers/web/repo/view.go b/routers/web/repo/view.go
index 12b3aef505..938292a37a 100644
--- a/routers/web/repo/view.go
+++ b/routers/web/repo/view.go
@@ -502,7 +502,33 @@ func renderFile(ctx *context.Context, entry *git.TreeEntry, treeLink, rawLink st
 			lineNums := linesBytesCount(buf)
 			ctx.Data["NumLines"] = strconv.Itoa(lineNums)
 			ctx.Data["NumLinesSet"] = true
-			ctx.Data["FileContent"] = highlight.File(lineNums, blob.Name(), buf)
+
+			language := ""
+
+			indexFilename, worktree, deleteTemporaryFile, err := ctx.Repo.GitRepo.ReadTreeToTemporaryIndex(ctx.Repo.CommitID)
+			if err == nil {
+				defer deleteTemporaryFile()
+
+				filename2attribute2info, err := ctx.Repo.GitRepo.CheckAttribute(git.CheckAttributeOpts{
+					CachedOnly: true,
+					Attributes: []string{"linguist-language", "gitlab-language"},
+					Filenames:  []string{ctx.Repo.TreePath},
+					IndexFile:  indexFilename,
+					WorkTree:   worktree,
+				})
+				if err != nil {
+					log.Error("Unable to load attributes for %-v:%s. Error: %v", ctx.Repo.Repository, ctx.Repo.TreePath, err)
+				}
+
+				language = filename2attribute2info[ctx.Repo.TreePath]["linguist-language"]
+				if language == "" || language == "unspecified" {
+					language = filename2attribute2info[ctx.Repo.TreePath]["gitlab-language"]
+				}
+				if language == "unspecified" {
+					language = ""
+				}
+			}
+			ctx.Data["FileContent"] = highlight.File(lineNums, blob.Name(), language, buf)
 		}
 		if !isLFSFile {
 			if ctx.Repo.CanEnableEditor() {
diff --git a/services/gitdiff/gitdiff.go b/services/gitdiff/gitdiff.go
index 614f8104ec..33e66e89ec 100644
--- a/services/gitdiff/gitdiff.go
+++ b/services/gitdiff/gitdiff.go
@@ -31,7 +31,6 @@ import (
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/process"
 	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/util"
 
 	"github.com/sergi/go-diff/diffmatchpatch"
 	stdcharset "golang.org/x/net/html/charset"
@@ -178,6 +177,7 @@ func getLineContent(content string) string {
 
 // DiffSection represents a section of a DiffFile.
 type DiffSection struct {
+	file     *DiffFile
 	FileName string
 	Name     string
 	Lines    []*DiffLine
@@ -546,6 +546,11 @@ func (diffSection *DiffSection) GetComputedInlineDiffFor(diffLine *DiffLine) tem
 		diff2           string
 	)
 
+	language := ""
+	if diffSection.file != nil {
+		language = diffSection.file.Language
+	}
+
 	// try to find equivalent diff line. ignore, otherwise
 	switch diffLine.Type {
 	case DiffLineSection:
@@ -553,25 +558,25 @@ func (diffSection *DiffSection) GetComputedInlineDiffFor(diffLine *DiffLine) tem
 	case DiffLineAdd:
 		compareDiffLine = diffSection.GetLine(DiffLineDel, diffLine.RightIdx)
 		if compareDiffLine == nil {
-			return template.HTML(highlight.Code(diffSection.FileName, diffLine.Content[1:]))
+			return template.HTML(highlight.Code(diffSection.FileName, language, diffLine.Content[1:]))
 		}
 		diff1 = compareDiffLine.Content
 		diff2 = diffLine.Content
 	case DiffLineDel:
 		compareDiffLine = diffSection.GetLine(DiffLineAdd, diffLine.LeftIdx)
 		if compareDiffLine == nil {
-			return template.HTML(highlight.Code(diffSection.FileName, diffLine.Content[1:]))
+			return template.HTML(highlight.Code(diffSection.FileName, language, diffLine.Content[1:]))
 		}
 		diff1 = diffLine.Content
 		diff2 = compareDiffLine.Content
 	default:
 		if strings.IndexByte(" +-", diffLine.Content[0]) > -1 {
-			return template.HTML(highlight.Code(diffSection.FileName, diffLine.Content[1:]))
+			return template.HTML(highlight.Code(diffSection.FileName, language, diffLine.Content[1:]))
 		}
-		return template.HTML(highlight.Code(diffSection.FileName, diffLine.Content))
+		return template.HTML(highlight.Code(diffSection.FileName, language, diffLine.Content))
 	}
 
-	diffRecord := diffMatchPatch.DiffMain(highlight.Code(diffSection.FileName, diff1[1:]), highlight.Code(diffSection.FileName, diff2[1:]), true)
+	diffRecord := diffMatchPatch.DiffMain(highlight.Code(diffSection.FileName, language, diff1[1:]), highlight.Code(diffSection.FileName, language, diff2[1:]), true)
 	diffRecord = diffMatchPatch.DiffCleanupEfficiency(diffRecord)
 
 	return diffToHTML(diffSection.FileName, diffRecord, diffLine.Type)
@@ -597,6 +602,7 @@ type DiffFile struct {
 	IsProtected             bool
 	IsGenerated             bool
 	IsVendored              bool
+	Language                string
 }
 
 // GetType returns type of diff file.
@@ -1008,7 +1014,7 @@ func parseHunks(curFile *DiffFile, maxLines, maxLineCharacters int, input *bufio
 			line := sb.String()
 
 			// Create a new section to represent this hunk
-			curSection = &DiffSection{}
+			curSection = &DiffSection{file: curFile}
 			lastLeftIdx = -1
 			curFile.Sections = append(curFile.Sections, curSection)
 
@@ -1048,7 +1054,7 @@ func parseHunks(curFile *DiffFile, maxLines, maxLineCharacters int, input *bufio
 			rightLine++
 			if curSection == nil {
 				// Create a new section to represent this hunk
-				curSection = &DiffSection{}
+				curSection = &DiffSection{file: curFile}
 				curFile.Sections = append(curFile.Sections, curSection)
 				lastLeftIdx = -1
 			}
@@ -1074,7 +1080,7 @@ func parseHunks(curFile *DiffFile, maxLines, maxLineCharacters int, input *bufio
 			}
 			if curSection == nil {
 				// Create a new section to represent this hunk
-				curSection = &DiffSection{}
+				curSection = &DiffSection{file: curFile}
 				curFile.Sections = append(curFile.Sections, curSection)
 				lastLeftIdx = -1
 			}
@@ -1094,7 +1100,7 @@ func parseHunks(curFile *DiffFile, maxLines, maxLineCharacters int, input *bufio
 			lastLeftIdx = -1
 			if curSection == nil {
 				// Create a new section to represent this hunk
-				curSection = &DiffSection{}
+				curSection = &DiffSection{file: curFile}
 				curFile.Sections = append(curFile.Sections, curSection)
 			}
 			curSection.Lines = append(curSection.Lines, diffLine)
@@ -1302,23 +1308,15 @@ func GetDiffRangeWithWhitespaceBehavior(gitRepo *git.Repository, beforeCommitID,
 	var checker *git.CheckAttributeReader
 
 	if git.CheckGitVersionAtLeast("1.7.8") == nil {
-		indexFilename, deleteTemporaryFile, err := gitRepo.ReadTreeToTemporaryIndex(afterCommitID)
+		indexFilename, worktree, deleteTemporaryFile, err := gitRepo.ReadTreeToTemporaryIndex(afterCommitID)
 		if err == nil {
 			defer deleteTemporaryFile()
-			workdir, err := os.MkdirTemp("", "empty-work-dir")
-			if err != nil {
-				log.Error("Unable to create temporary directory: %v", err)
-				return nil, err
-			}
-			defer func() {
-				_ = util.RemoveAll(workdir)
-			}()
 
 			checker = &git.CheckAttributeReader{
-				Attributes: []string{"linguist-vendored", "linguist-generated"},
+				Attributes: []string{"linguist-vendored", "linguist-generated", "linguist-language", "gitlab-language"},
 				Repo:       gitRepo,
 				IndexFile:  indexFilename,
-				WorkTree:   workdir,
+				WorkTree:   worktree,
 			}
 			ctx, cancel := context.WithCancel(git.DefaultContext)
 			if err := checker.Init(ctx); err != nil {
@@ -1361,6 +1359,11 @@ func GetDiffRangeWithWhitespaceBehavior(gitRepo *git.Repository, beforeCommitID,
 						gotGenerated = generated == "false"
 					}
 				}
+				if language, has := attrs["linguist-language"]; has && language != "unspecified" && language != "" {
+					diffFile.Language = language
+				} else if language, has := attrs["gitlab-language"]; has && language != "unspecified" && language != "" {
+					diffFile.Language = language
+				}
 			} else {
 				log.Error("Unexpected error: %v", err)
 			}
diff --git a/services/gitdiff/gitdiff_test.go b/services/gitdiff/gitdiff_test.go
index aefd396ebb..c6c6f3b0e3 100644
--- a/services/gitdiff/gitdiff_test.go
+++ b/services/gitdiff/gitdiff_test.go
@@ -533,7 +533,7 @@ func TestGetDiffRangeWithWhitespaceBehavior(t *testing.T) {
 
 func TestDiffToHTML_14231(t *testing.T) {
 	setting.Cfg = ini.Empty()
-	diffRecord := diffMatchPatch.DiffMain(highlight.Code("main.v", "		run()\n"), highlight.Code("main.v", "		run(db)\n"), true)
+	diffRecord := diffMatchPatch.DiffMain(highlight.Code("main.v", "", "		run()\n"), highlight.Code("main.v", "", "		run(db)\n"), true)
 	diffRecord = diffMatchPatch.DiffCleanupEfficiency(diffRecord)
 
 	expected := `		<span class="n">run</span><span class="added-code"><span class="o">(</span><span class="n">db</span></span><span class="o">)</span>`