Handle symlinks and submodules in diffcut (#1185)

git/api/diff.go

@@ -407,14 +407,13 @@ func (g *Git) DiffCut(
 		return parser.HunkHeader{}, parser.Hunk{}, fmt.Errorf("failed to find the list of changed files: %w", err)
 	}
 
-	var (
+	var oldSHA, newSHA string
-		oldSHA, newSHA string
-		filePath       string
-	)
 
 	for _, entry := range diffEntries {
-		switch entry.Status {
+		if entry.Status == parser.DiffStatusRenamed || entry.Status == parser.DiffStatusCopied {
-		case parser.DiffStatusRenamed, parser.DiffStatusCopied:
+			// Entries with the status 'R' and 'C' output two paths: the old path and the new path.
+			// Using the params.LineStartNew flag to match the path with the entry's old or new path.
+
 			if entry.Path != path && entry.OldPath != path {
 				continue
 			}
@@ -427,34 +426,79 @@ func (g *Git) DiffCut(
 				msg := "for renamed files provide the old file name if commenting the old lines"
 				return parser.HunkHeader{}, parser.Hunk{}, errors.InvalidArgument(msg)
 			}
-		default:
+		} else if entry.Path != path {
-			if entry.Path != path {
+			// All other statuses output just one path: If the path doesn't match it, proceed with the next entry.
-				continue
+			continue
-			}
 		}
 
+		rawFileMode := entry.OldFileMode
+		if params.LineStartNew {
+			rawFileMode = entry.NewFileMode
+		}
+
+		fileType, _, err := parseTreeNodeMode(rawFileMode)
+		if err != nil {
+			return parser.HunkHeader{}, parser.Hunk{},
+				fmt.Errorf("failed to parse file mode %s for path %s: %w", rawFileMode, path, err)
+		}
+
+		switch fileType {
+		default:
+			return parser.HunkHeader{}, parser.Hunk{}, errors.Internal(nil, "unrecognized object type")
+		case TreeNodeTypeCommit:
+			msg := "code comment is not allowed on a submodule"
+			return parser.HunkHeader{}, parser.Hunk{}, errors.InvalidArgument(msg)
+		case TreeNodeTypeTree:
+			msg := "code comment is not allowed on a directory"
+			return parser.HunkHeader{}, parser.Hunk{}, errors.InvalidArgument(msg)
+		case TreeNodeTypeBlob:
+			// a blob is what we want
+		}
+
+		var hunkHeader parser.HunkHeader
+		var hunk parser.Hunk
+
 		switch entry.Status {
 		case parser.DiffStatusRenamed, parser.DiffStatusCopied, parser.DiffStatusModified:
-			// For modified and renamed compare file blobs directly.
+			// For modified and renamed compare file blob SHAs directly.
 			oldSHA = entry.OldBlobSHA
 			newSHA = entry.NewBlobSHA
-		case parser.DiffStatusAdded, parser.DiffStatusDeleted:
+			hunkHeader, hunk, err = g.diffCutFromHunk(ctx, repoPath, oldSHA, newSHA, params)
-			// For added and deleted compare commits, but with the provided path.
+		case parser.DiffStatusAdded, parser.DiffStatusDeleted, parser.DiffStatusType:
-			oldSHA = targetRef
+			// for added and deleted files read the file content directly
-			newSHA = sourceRef
+			if params.LineStartNew {
-			filePath = entry.Path
+				hunkHeader, hunk, err = g.diffCutFromBlob(ctx, repoPath, true, entry.NewBlobSHA, params)
+			} else {
+				hunkHeader, hunk, err = g.diffCutFromBlob(ctx, repoPath, false, entry.OldBlobSHA, params)
+			}
+		default:
+			return parser.HunkHeader{}, parser.Hunk{},
+				fmt.Errorf("unrecognized git diff file status=%c for path=%s", entry.Status, path)
+		}
+		if err != nil {
+			return parser.HunkHeader{}, parser.Hunk{},
+				fmt.Errorf("failed to extract hunk for git diff file status=%c path=%s: %w", entry.Status, path, err)
 		}
 
-		break
+		// The returned diff hunk will be stored in the DB and will only be used for display, as a reference.
+		// Therefore, we trim too long lines to protect the system and the DB.
+		const maxLineLen = 200
+		parser.LimitLineLen(&hunk.Lines, maxLineLen)
+
+		return hunkHeader, hunk, nil
 	}
 
-	if newSHA == "" {
+	return parser.HunkHeader{}, parser.Hunk{}, errors.NotFound("path not found")
-		return parser.HunkHeader{}, parser.Hunk{}, errors.NotFound("file %s not found in the diff", path)
+}
-	}
 
-	// next pull the diff cut for the requested file
+func (g *Git) diffCutFromHunk(
-
+	ctx context.Context,
-	pipeRead, pipeWrite = io.Pipe()
+	repoPath string,
+	oldSHA string,
+	newSHA string,
+	params parser.DiffCutParams,
+) (parser.HunkHeader, parser.Hunk, error) {
+	pipeRead, pipeWrite := io.Pipe()
 	stderr := bytes.NewBuffer(nil)
 	go func() {
 		var err error
@@ -470,11 +514,6 @@ func (g *Git) DiffCut(
 			command.WithFlag("--unified=100000000"),
 			command.WithArg(oldSHA),
 			command.WithArg(newSHA))
-		if filePath != "" {
-			cmd.Add(
-				command.WithFlag("--merge-base"),
-				command.WithPostSepArg(filePath))
-		}
 
 		err = cmd.Run(ctx,
 			command.WithDir(repoPath),
@@ -495,6 +534,75 @@ func (g *Git) DiffCut(
 	return diffCutHeader, linesHunk, nil
 }
 
+func (g *Git) diffCutFromBlob(
+	ctx context.Context,
+	repoPath string,
+	asAdded bool,
+	sha string,
+	params parser.DiffCutParams,
+) (parser.HunkHeader, parser.Hunk, error) {
+	pipeRead, pipeWrite := io.Pipe()
+	go func() {
+		var err error
+
+		defer func() {
+			// If running of the command below fails, make the pipe reader also fail with the same error.
+			_ = pipeWrite.CloseWithError(err)
+		}()
+
+		cmd := command.New("cat-file",
+			command.WithFlag("-p"),
+			command.WithArg(sha))
+
+		err = cmd.Run(ctx,
+			command.WithDir(repoPath),
+			command.WithStdout(pipeWrite))
+	}()
+
+	cutHeader, cut, err := parser.BlobCut(pipeRead, params)
+	if err != nil {
+		// Next check if reading the git diff output caused an error
+		return parser.HunkHeader{}, parser.Hunk{}, err
+	}
+
+	// Convert parser.CutHeader to parser.HunkHeader and parser.Cut to parser.Hunk.
+
+	var hunkHeader parser.HunkHeader
+	var hunk parser.Hunk
+
+	if asAdded {
+		for i := range cut.Lines {
+			cut.Lines[i] = "+ " + cut.Lines[i]
+		}
+
+		hunkHeader = parser.HunkHeader{
+			NewLine: cutHeader.Line,
+			NewSpan: cutHeader.Span,
+		}
+
+		hunk = parser.Hunk{
+			HunkHeader: parser.HunkHeader{NewLine: cut.Line, NewSpan: cut.Span},
+			Lines:      cut.Lines,
+		}
+	} else {
+		for i := range cut.Lines {
+			cut.Lines[i] = "- " + cut.Lines[i]
+		}
+
+		hunkHeader = parser.HunkHeader{
+			OldLine: cutHeader.Line,
+			OldSpan: cutHeader.Span,
+		}
+
+		hunk = parser.Hunk{
+			HunkHeader: parser.HunkHeader{OldLine: cut.Line, OldSpan: cut.Span},
+			Lines:      cut.Lines,
+		}
+	}
+
+	return hunkHeader, hunk, nil
+}
+
 func (g *Git) DiffFileName(ctx context.Context,
 	repoPath string,
 	baseRef string,

git/parser/diff_cut.go

@@ -17,7 +17,9 @@ package parser
 import (
 	"bufio"
 	"errors"
+	"fmt"
 	"io"
+	"unicode/utf8"
 )
 
 type DiffFileHeader struct {
@@ -239,6 +241,97 @@ again:
 	return
 }
 
+// BlobCut parses raw file and returns lines specified with the parameter.
+func BlobCut(r io.Reader, params DiffCutParams) (CutHeader, Cut, error) {
+	scanner := bufio.NewScanner(r)
+
+	var (
+		err               error
+		lineNumber        int
+		inCut             bool
+		cutStart, cutSpan int
+		cutLines          []string
+	)
+
+	extStart := params.LineStart - params.BeforeLines
+	extEnd := params.LineEnd + params.AfterLines
+	linesNeeded := params.LineEnd - params.LineStart + 1
+
+	for {
+		if !scanner.Scan() {
+			err = scanner.Err()
+			break
+		}
+
+		lineNumber++
+		line := scanner.Text()
+
+		if !utf8.ValidString(line) {
+			return CutHeader{}, Cut{}, ErrBinaryFile
+		}
+
+		if lineNumber > extEnd {
+			break // exceeded the requested line range
+		}
+
+		if lineNumber < extStart {
+			// not yet in the requested line range
+			continue
+		}
+
+		if !inCut {
+			cutStart = lineNumber
+			inCut = true
+		}
+		cutLines = append(cutLines, line)
+		cutSpan++
+
+		if lineNumber >= params.LineStart && lineNumber <= params.LineEnd {
+			linesNeeded--
+		}
+
+		if len(cutLines) >= params.LineLimit {
+			break
+		}
+	}
+
+	if errors.Is(err, bufio.ErrTooLong) {
+		// By default, the max token size is 65536 (bufio.MaxScanTokenSize).
+		// If the file contains a line that is longer than this we treat it as a binary file.
+		return CutHeader{}, Cut{}, ErrBinaryFile
+	}
+
+	if err != nil && !errors.Is(err, io.EOF) {
+		return CutHeader{}, Cut{}, fmt.Errorf("failed to parse blob cut: %w", err)
+	}
+
+	if !inCut || linesNeeded > 0 {
+		return CutHeader{}, Cut{}, ErrHunkNotFound
+	}
+
+	// the cut header is hunk-like header (with Line and Span) that describes the requested lines exactly
+	ch := CutHeader{Line: params.LineStart, Span: params.LineEnd - params.LineStart + 1}
+
+	// the cut includes the requested lines and few more lines specified with the BeforeLines and AfterLines.
+	c := Cut{CutHeader: CutHeader{Line: cutStart, Span: cutSpan}, Lines: cutLines}
+
+	return ch, c, nil
+}
+
+func LimitLineLen(lines *[]string, maxLen int) {
+outer:
+	for idxLine, line := range *lines {
+		var l int
+		for idxRune := range line {
+			l++
+			if l > maxLen {
+				(*lines)[idxLine] = line[:idxRune] + "…" // append the ellipsis to indicate that the line was trimmed.
+				continue outer
+			}
+		}
+	}
+}
+
 type strCircBuf struct {
 	head    int
 	entries []string

git/parser/diff_cut_test.go

@@ -237,6 +237,88 @@ index af7864ba..541cb64f 100644
 	}
 }
 
+func TestBlobCut(t *testing.T) {
+	const input = `1
+2
+3
+4
+5
+6`
+
+	tests := []struct {
+		name         string
+		params       DiffCutParams
+		expCutHeader CutHeader
+		expCut       Cut
+		expError     error
+	}{
+		{
+			name:         "first 3 lines",
+			params:       DiffCutParams{LineStart: 1, LineEnd: 3, LineLimit: 40},
+			expCutHeader: CutHeader{Line: 1, Span: 3},
+			expCut:       Cut{CutHeader: CutHeader{Line: 1, Span: 3}, Lines: []string{"1", "2", "3"}},
+		},
+		{
+			name:         "last 2 lines",
+			params:       DiffCutParams{LineStart: 5, LineEnd: 6, LineLimit: 40},
+			expCutHeader: CutHeader{Line: 5, Span: 2},
+			expCut:       Cut{CutHeader: CutHeader{Line: 5, Span: 2}, Lines: []string{"5", "6"}},
+		},
+		{
+			name:         "first 3 lines with 1 more",
+			params:       DiffCutParams{LineStart: 1, LineEnd: 3, BeforeLines: 1, AfterLines: 1, LineLimit: 40},
+			expCutHeader: CutHeader{Line: 1, Span: 3},
+			expCut:       Cut{CutHeader: CutHeader{Line: 1, Span: 4}, Lines: []string{"1", "2", "3", "4"}},
+		},
+		{
+			name:         "last 2 lines with 2 more",
+			params:       DiffCutParams{LineStart: 5, LineEnd: 6, BeforeLines: 2, AfterLines: 2, LineLimit: 40},
+			expCutHeader: CutHeader{Line: 5, Span: 2},
+			expCut:       Cut{CutHeader: CutHeader{Line: 3, Span: 4}, Lines: []string{"3", "4", "5", "6"}},
+		},
+		{
+			name:         "mid range",
+			params:       DiffCutParams{LineStart: 2, LineEnd: 4, BeforeLines: 100, AfterLines: 100, LineLimit: 40},
+			expCutHeader: CutHeader{Line: 2, Span: 3},
+			expCut:       Cut{CutHeader: CutHeader{Line: 1, Span: 6}, Lines: []string{"1", "2", "3", "4", "5", "6"}},
+		},
+		{
+			name:     "out of range 1",
+			params:   DiffCutParams{LineStart: 15, LineEnd: 17, LineLimit: 40},
+			expError: ErrHunkNotFound,
+		},
+		{
+			name:     "out of range 2",
+			params:   DiffCutParams{LineStart: 5, LineEnd: 7, BeforeLines: 1, AfterLines: 1, LineLimit: 40},
+			expError: ErrHunkNotFound,
+		},
+		{
+			name:         "limited",
+			params:       DiffCutParams{LineStart: 3, LineEnd: 4, BeforeLines: 1, AfterLines: 1, LineLimit: 3},
+			expCutHeader: CutHeader{Line: 3, Span: 2},
+			expCut:       Cut{CutHeader: CutHeader{Line: 2, Span: 3}, Lines: []string{"2", "3", "4"}},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			ch, c, err := BlobCut(strings.NewReader(input), test.params)
+			if err != test.expError { //nolint:errorlint // it's a unit test and no errors are wrapped
+				t.Errorf("test failed with error: %s", err.Error())
+				return
+			}
+
+			if want, got := test.expCutHeader, ch; want != got {
+				t.Errorf("cut header: want=%+v got: %+v", want, got)
+			}
+
+			if want, got := test.expCut, c; !reflect.DeepEqual(want, got) {
+				t.Errorf("cut: want=%+v got: %+v", want, got)
+			}
+		})
+	}
+}
+
 func TestStrCircBuf(t *testing.T) {
 	tests := []struct {
 		name string

git/parser/diff_raw.go

@@ -24,23 +24,29 @@ import (
 type DiffStatus byte
 
 const (
-	DiffStatusModified = 'M'
+	DiffStatusModified DiffStatus = 'M'
-	DiffStatusAdded    = 'A'
+	DiffStatusAdded    DiffStatus = 'A'
-	DiffStatusDeleted  = 'D'
+	DiffStatusDeleted  DiffStatus = 'D'
-	DiffStatusRenamed  = 'R'
+	DiffStatusRenamed  DiffStatus = 'R'
-	DiffStatusCopied   = 'C'
+	DiffStatusCopied   DiffStatus = 'C'
-	DiffStatusType     = 'T'
+	DiffStatusType     DiffStatus = 'T'
 )
 
-type DiffRawFile struct {
+func (s DiffStatus) String() string {
-	OldBlobSHA string
+	return fmt.Sprintf("%c", s)
-	NewBlobSHA string
-	Status     byte
-	OldPath    string
-	Path       string
 }
 
-var regexpDiffRaw = regexp.MustCompile(`:\d{6} \d{6} ([0-9a-f]+) ([0-9a-f]+) (\w)(\d*)`)
+type DiffRawFile struct {
+	OldFileMode string
+	NewFileMode string
+	OldBlobSHA  string
+	NewBlobSHA  string
+	Status      DiffStatus
+	OldPath     string
+	Path        string
+}
+
+var regexpDiffRaw = regexp.MustCompile(`:(\d{6}) (\d{6}) ([0-9a-f]+) ([0-9a-f]+) (\w)(\d*)`)
 
 // DiffRaw parses raw git diff output (git diff --raw). Each entry (a line) is a changed file.
 // The format is:
@@ -72,7 +78,7 @@ func DiffRaw(r io.Reader) ([]DiffRawFile, error) {
 
 		path = scan.Text()
 
-		status := groups[3][0]
+		status := DiffStatus(groups[5][0])
 		switch status {
 		case DiffStatusRenamed, DiffStatusCopied:
 			if !scan.Scan() {
@@ -86,11 +92,13 @@ func DiffRaw(r io.Reader) ([]DiffRawFile, error) {
 		}
 
 		result = append(result, DiffRawFile{
-			OldBlobSHA: groups[1],
+			OldFileMode: groups[1],
-			NewBlobSHA: groups[2],
+			NewFileMode: groups[2],
-			Status:     status,
+			OldBlobSHA:  groups[3],
-			OldPath:    oldPath,
+			NewBlobSHA:  groups[4],
-			Path:       path,
+			Status:      status,
+			OldPath:     oldPath,
+			Path:        path,
 		})
 	}
 	if err := scan.Err(); err != nil {

git/parser/errors.go

@@ -14,9 +14,10 @@
 
 package parser
 
-import "errors"
+import "github.com/harness/gitness/errors"
 
 var (
-	ErrSHADoesNotMatch = errors.New("sha does not match")
+	ErrSHADoesNotMatch = errors.InvalidArgument("sha does not match")
-	ErrHunkNotFound    = errors.New("hunk not found")
+	ErrHunkNotFound    = errors.NotFound("hunk not found")
+	ErrBinaryFile      = errors.InvalidArgument("can't handle a binary file")
 )

git/parser/hunk.go

@@ -33,6 +33,16 @@ type HunkHeader struct {
 	Text    string
 }
 
+type Cut struct {
+	CutHeader
+	Lines []string
+}
+
+type CutHeader struct {
+	Line int
+	Span int
+}
+
 var regExpHunkHeader = regexp.MustCompile(`^@@ -([0-9]+)(,([0-9]+))? \+([0-9]+)(,([0-9]+))? @@( (.+))?$`)
 
 func (h *HunkHeader) IsZero() bool {