Support Apple Diff timestamps

diff/diff.go

@@ -120,6 +120,10 @@ const onlyInMessage = "Only in %s: %s\n"
 // See https://www.gnu.org/software/diffutils/manual/html_node/Detailed-Unified.html.
 const diffTimeParseLayout = "2006-01-02 15:04:05 -0700"
 
+// Apple's diff is based on freebsd diff, which uses a timestamp format that does
+// not include the timezone offset.
+const diffTimeParseWithoutTZLayout = "2006-01-02 15:04:05"
+
 // diffTimeFormatLayout is the layout used to format (i.e., print) the time in unified diff file
 // header timestamps.
 // See https://www.gnu.org/software/diffutils/manual/html_node/Detailed-Unified.html.

diff/diff_test.go

@@ -850,12 +850,14 @@ func TestParseFileDiffAndPrintFileDiff(t *testing.T) {
 
 func TestParseMultiFileDiffAndPrintMultiFileDiff(t *testing.T) {
 	tests := []struct {
-		filename      string
-		wantParseErr  error
-		wantFileDiffs int // How many instances of diff.FileDiff are expected.
+		filename        string
+		wantParseErr    error
+		wantFileDiffs   int    // How many instances of diff.FileDiff are expected.
+		wantOutFileName string // If non-empty, the name of the file containing the expected output.
 	}{
 		{filename: "sample_multi_file.diff", wantFileDiffs: 2},
 		{filename: "sample_multi_file_single.diff", wantFileDiffs: 1},
+		{filename: "sample_multi_file_single_apple_in.diff", wantFileDiffs: 1, wantOutFileName: "sample_multi_file_single_apple_out.diff"},
 		{filename: "sample_multi_file_new.diff", wantFileDiffs: 3},
 		{filename: "sample_multi_file_deleted.diff", wantFileDiffs: 3},
 		{filename: "sample_multi_file_rename.diff", wantFileDiffs: 3},
@@ -892,6 +894,12 @@ func TestParseMultiFileDiffAndPrintMultiFileDiff(t *testing.T) {
 		if err != nil {
 			t.Errorf("%s: PrintMultiFileDiff: %s", test.filename, err)
 		}
+		if test.wantOutFileName != "" {
+			diffData, err = ioutil.ReadFile(filepath.Join("testdata", test.wantOutFileName))
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
 		if !bytes.Equal(printed, diffData) {
 			t.Errorf("%s: printed multi-file diff != original multi-file diff\n\n# PrintMultiFileDiff output - Original:\n%s", test.filename, cmp.Diff(diffData, printed))
 		}

diff/parse.go

@@ -254,7 +254,6 @@ func (r *FileDiffReader) ReadFileHeaders() (origName, newName string, origTimest
 				"", nil, nil, nil
 		}
 	}
-
 	origName, origTimestamp, err = r.readOneFileHeader([]byte("--- "))
 	if err != nil {
 		return "", "", nil, nil, err
@@ -307,10 +306,16 @@ func (r *FileDiffReader) readOneFileHeader(prefix []byte) (filename string, time
 	parts := strings.SplitN(trimmedLine, "\t", 2)
 	filename = parts[0]
 	if len(parts) == 2 {
+		var ts time.Time
 		// Timestamp is optional, but this header has it.
-		ts, err := time.Parse(diffTimeParseLayout, parts[1])
+		ts, err = time.Parse(diffTimeParseLayout, parts[1])
 		if err != nil {
-			return "", nil, err
+			var err1 error
+			ts, err1 = time.Parse(diffTimeParseWithoutTZLayout, parts[1])
+			if err1 != nil {
+				return "", nil, err
+			}
+			err = nil
 		}
 		timestamp = &ts
 	}

diff/testdata/sample_multi_file_single_apple_in.diff

@@ -0,0 +1,29 @@
+diff -u a/oldname1 b/newname1
+--- oldname1	2009-10-11 15:12:20
++++ newname1	2009-10-11 15:12:30
+@@ -1,3 +1,9 @@
++This is an important
++notice! It should
++therefore be located at
++the beginning of this
++document!
++
+ This part of the
+ document has stayed the
+ same from version to
+@@ -5,16 +11,10 @@
+ be shown if it doesn't
+ change.  Otherwise, that
+ would not be helping to
+-compress the size of the
+-changes.
+-
+-This paragraph contains
+-text that is outdated.
+-It will be deleted in the
+-near future.
++compress anything.
+
+ It is important to spell
+-check this dokument. On
++check this document. On

diff/testdata/sample_multi_file_single_apple_out.diff

@@ -0,0 +1,29 @@
+diff -u a/oldname1 b/newname1
+--- oldname1	2009-10-11 15:12:20.000000000 +0000
++++ newname1	2009-10-11 15:12:30.000000000 +0000
+@@ -1,3 +1,9 @@
++This is an important
++notice! It should
++therefore be located at
++the beginning of this
++document!
++
+ This part of the
+ document has stayed the
+ same from version to
+@@ -5,16 +11,10 @@
+ be shown if it doesn't
+ change.  Otherwise, that
+ would not be helping to
+-compress the size of the
+-changes.
+-
+-This paragraph contains
+-text that is outdated.
+-It will be deleted in the
+-near future.
++compress anything.
+
+ It is important to spell
+-check this dokument. On
++check this document. On