Add support for parsing header timestamps without fractional seconds.

We need to use a different layout string for parsing and printing,
since we only want to change the parsing behavior (not printing
behavior).

Add test for it.

Resolves #17.

diff/diff.go

@@ -59,10 +59,15 @@ var (
 
 const hunkHeader = "@@ -%d,%d +%d,%d @@"
 
-// diffTimeFormat is the time format string for unified diff file
-// header timestamps. See
-// http://www.gnu.org/software/diffutils/manual/html_node/Detailed-Unified.html.
-const diffTimeFormat = "2006-01-02 15:04:05.000000000 -0700"
+// diffTimeParseLayout is the layout used to parse the time in unified diff file
+// header timestamps.
+// See https://www.gnu.org/software/diffutils/manual/html_node/Detailed-Unified.html.
+const diffTimeParseLayout = "2006-01-02 15:04:05 -0700"
+
+// 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.
+const diffTimeFormatLayout = "2006-01-02 15:04:05.000000000 -0700"
 
 func (s *Stat) add(o Stat) {
 	s.Added += o.Added

diff/diff_test.go

@@ -108,6 +108,15 @@ func TestParseFileDiffHeaders(t *testing.T) {
 				NewTime:  &pbtypes.Timestamp{Seconds: 1255273950},
 			},
 		},
+		{
+			filename: "sample_file_no_fractional_seconds.diff",
+			wantDiff: &FileDiff{
+				OrigName: "goyaml.go",
+				OrigTime: &pbtypes.Timestamp{Seconds: 1322164040},
+				NewName:  "goyaml.go",
+				NewTime:  &pbtypes.Timestamp{Seconds: 1322486679},
+			},
+		},
 		{
 			filename: "sample_file_extended.diff",
 			wantDiff: &FileDiff{

diff/parse.go

@@ -267,7 +267,7 @@ func (r *FileDiffReader) readOneFileHeader(prefix []byte) (filename string, time
 	filename = parts[0]
 	if len(parts) == 2 {
 		// Timestamp is optional, but this header has it.
-		ts, err := time.Parse(diffTimeFormat, parts[1])
+		ts, err := time.Parse(diffTimeParseLayout, parts[1])
 		if err != nil {
 			return "", nil, err
 		}

diff/print.go

@@ -71,7 +71,7 @@ func printFileHeader(w io.Writer, prefix string, filename string, timestamp *tim
 		return err
 	}
 	if timestamp != nil {
-		if _, err := fmt.Fprint(w, "\t", timestamp.Format(diffTimeFormat)); err != nil {
+		if _, err := fmt.Fprint(w, "\t", timestamp.Format(diffTimeFormatLayout)); err != nil {
 			return err
 		}
 	}

diff/testdata/sample_file_no_fractional_seconds.diff

@@ -0,0 +1,11 @@
+--- goyaml.go	2011-11-24 19:47:20 +0000
++++ goyaml.go	2011-11-28 13:24:39 +0000
+@@ -256,7 +256,7 @@
+ 	switch v.Kind() {
+ 	case reflect.String:
+ 		return len(v.String()) == 0
+-	case reflect.Interface:
++	case reflect.Interface, reflect.Ptr:
+ 		return v.IsNil()
+ 	case reflect.Slice:
+ 		return v.Len() == 0