handle no trailing EOL git message

gitrpc/internal/parser/diff_cut.go

@@ -103,16 +103,16 @@ func DiffCut(r io.Reader, params types.DiffCutParams) (types.HunkHeader, types.H
 
 	linesBefore = linesBeforeBuf.lines()
 	if !errors.Is(err, io.EOF) {
-		for i := 0; i < params.AfterLines && scanner.Scan(); i++ {
+		for i := 0; i < params.AfterLines; i++ {
-			line := scanner.Text()
+			line, _, err := scanHunkLine(scanner)
+			if err != nil {
+				return types.HunkHeader{}, types.Hunk{}, err
+			}
 			if line == "" {
 				break
 			}
 			linesAfter = append(linesAfter, line)
 		}
-		if err = scanner.Err(); err != nil {
-			return types.HunkHeader{}, types.Hunk{}, err
-		}
 	}
 
 	diffCutHeaderLines := diffCutHeader
@@ -185,22 +185,34 @@ const (
 	actionAdded     diffAction = '+'
 )
 
-func scanHunkLine(scan *bufio.Scanner) (string, diffAction, error) {
+func scanHunkLine(scan *bufio.Scanner) (line string, action diffAction, err error) {
+again:
+	action = actionUnchanged
+
 	if !scan.Scan() {
-		return "", actionUnchanged, scan.Err()
+		err = scan.Err()
+		return
 	}
 
-	line := scan.Text()
+	line = scan.Text()
 	if line == "" {
-		return "", actionUnchanged, types.ErrHunkNotFound // should not happen: empty line in diff output
+		err = types.ErrHunkNotFound // should not happen: empty line in diff output
+		return
+	}
+
+	action = diffAction(line[0])
+	if action == '\\' { // handle the "\ No newline at end of file" line
+		goto again
 	}
 
-	action := diffAction(line[0])
 	if action != actionRemoved && action != actionAdded && action != actionUnchanged {
-		return "", actionUnchanged, nil
+		// treat this as the end of hunk
+		line = ""
+		action = actionUnchanged
+		return
 	}
 
-	return line, action, nil
+	return
 }
 
 type strCircBuf struct {

gitrpc/internal/parser/diff_cut_test.go

@@ -142,6 +142,93 @@ func TestDiffCut(t *testing.T) {
 	}
 }
 
+func TestDiffCutNoEOLInOld(t *testing.T) {
+	const input = `diff --git a/test.txt b/test.txt
+index 541cb64f..047d7ee2 100644
+--- a/test.txt
++++ b/test.txt
+@@ -1 +1,4 @@
+-test
+\ No newline at end of file
++123
++456
++789
+`
+
+	hh, h, err := DiffCut(
+		strings.NewReader(input),
+		types.DiffCutParams{
+			LineStart:    3,
+			LineStartNew: true,
+			LineEnd:      3,
+			LineEndNew:   true,
+			BeforeLines:  1,
+			AfterLines:   1,
+			LineLimit:    100,
+		},
+	)
+	if err != nil {
+		t.Errorf("got error: %v", err)
+		return
+	}
+
+	expectedHH := types.HunkHeader{OldLine: 2, OldSpan: 0, NewLine: 3, NewSpan: 1}
+	if expectedHH != hh {
+		t.Errorf("expected hunk header: %+v, but got: %+v", expectedHH, hh)
+	}
+
+	expectedHunkLines := types.Hunk{
+		HunkHeader: types.HunkHeader{OldLine: 2, OldSpan: 0, NewLine: 2, NewSpan: 2},
+		Lines:      []string{"+456", "+789"},
+	}
+	if !reflect.DeepEqual(expectedHunkLines, h) {
+		t.Errorf("expected hunk header: %+v, but got: %+v", expectedHunkLines, h)
+	}
+}
+
+func TestDiffCutNoEOLInNew(t *testing.T) {
+	const input = `diff --git a/test.txt b/test.txt
+index af7864ba..541cb64f 100644
+--- a/test.txt
++++ b/test.txt
+@@ -1,3 +1 @@
+-123
+-456
+-789
++test
+\ No newline at end of file
+`
+	hh, h, err := DiffCut(
+		strings.NewReader(input),
+		types.DiffCutParams{
+			LineStart:    1,
+			LineStartNew: true,
+			LineEnd:      1,
+			LineEndNew:   true,
+			BeforeLines:  0,
+			AfterLines:   0,
+			LineLimit:    100,
+		},
+	)
+	if err != nil {
+		t.Errorf("got error: %v", err)
+		return
+	}
+
+	expectedHH := types.HunkHeader{OldLine: 1, OldSpan: 3, NewLine: 1, NewSpan: 1}
+	if expectedHH != hh {
+		t.Errorf("expected hunk header: %+v, but got: %+v", expectedHH, hh)
+	}
+
+	expectedHunkLines := types.Hunk{
+		HunkHeader: types.HunkHeader{OldLine: 1, OldSpan: 3, NewLine: 1, NewSpan: 1},
+		Lines:      []string{"-123", "-456", "-789", "+test"},
+	}
+	if !reflect.DeepEqual(expectedHunkLines, h) {
+		t.Errorf("expected hunk header: %+v, but got: %+v", expectedHunkLines, h)
+	}
+}
+
 func TestStrCircBuf(t *testing.T) {
 	tests := []struct {
 		name string