Implement -u/--update so creation times can be used on all remotes - #226

docs/content/docs.md

@@ -457,6 +457,25 @@ of timeouts or bigger if you have lots of bandwidth and a fast remote.
 
 The default is to run 4 file transfers in parallel.
 
+### -u, --update ###
+
+This forces rclone to skip any files which exist on the destination
+and have a modified time that is newer than the source file.
+
+If an existing destination file has a modification time equal (within
+the computed modify window precision) to the source file's, it will be
+updated if the sizes are different.
+
+On remotes which don't support mod time directly the time checked will
+be the uploaded time.  This means that if uploading to one of these
+remoes, rclone will skip any files which exist on the destination and
+have an uploaded time that is newer than the modification time of the
+source file.
+
+This can be useful when transferring to a remote which doesn't support
+mod times directly as it is more accurate than a `--size-only` check
+and faster than using `--checksum`.
+
 ### -v, --verbose ###
 
 If you set this flag, rclone will become very verbose telling you

fs/config.go

@@ -81,6 +81,7 @@ var (
 	deleteDuring    = pflag.BoolP("delete-during", "", false, "When synchronizing, delete files during transfer (default)")
 	deleteAfter     = pflag.BoolP("delete-after", "", false, "When synchronizing, delete files on destination after transfering")
 	lowLevelRetries = pflag.IntP("low-level-retries", "", 10, "Number of low level retries to do.")
+	updateOlder     = pflag.BoolP("update", "u", false, "Skip files that are newer on the destination.")
 	bwLimit         SizeSuffix
 
 	// Key to use for password en/decryption.
@@ -199,6 +200,7 @@ type ConfigInfo struct {
 	DeleteDuring       bool // Delete during checking/transfer
 	DeleteAfter        bool // Delete after successful transfer.
 	LowLevelRetries    int
+	UpdateOlder        bool // Skip files that are newer on the destination
 }
 
 // Transport returns an http.RoundTripper with the correct timeouts
@@ -288,6 +290,7 @@ func LoadConfig() {
 	Config.DumpBodies = *dumpBodies
 	Config.InsecureSkipVerify = *skipVerify
 	Config.LowLevelRetries = *lowLevelRetries
+	Config.UpdateOlder = *updateOlder
 
 	ConfigPath = *configFile
 

fs/operations.go

@@ -306,10 +306,38 @@ func checkOne(pair ObjectPair, out ObjectPairChan) {
 		Debug(src, "Destination exists, skipping")
 		return
 	}
-	// Check to see if changed or not
-	if Equal(src, dst) {
-		Debug(src, "Unchanged skipping")
-		return
+	// If UpdateOlder is in effect, skip if dst is newer than src
+	if Config.UpdateOlder {
+		srcModTime := src.ModTime()
+		dstModTime := dst.ModTime()
+		dt := dstModTime.Sub(srcModTime)
+		// If have a mutually agreed precision then use that
+		modifyWindow := Config.ModifyWindow
+		if modifyWindow == ModTimeNotSupported {
+			// Otherwise use 1 second as a safe default as
+			// the resolution of the time a file was
+			// uploaded.
+			modifyWindow = time.Second
+		}
+		switch {
+		case dt >= modifyWindow:
+			Debug(src, "Destination is newer than source, skipping")
+			return
+		case dt <= -modifyWindow:
+			Debug(src, "Destination is older than source, transferring")
+		default:
+			if src.Size() == dst.Size() {
+				Debug(src, "Destination mod time is within %v of source and sizes identical, skipping", modifyWindow)
+				return
+			}
+			Debug(src, "Destination mod time is within %v of source but sizes differ, transferring", modifyWindow)
+		}
+	} else {
+		// Check to see if changed or not
+		if Equal(src, dst) {
+			Debug(src, "Unchanged skipping")
+			return
+		}
 	}
 	out <- pair
 }

fs/operations_test.go

@@ -692,6 +692,40 @@ func TestSyncWithExcludeAndDeleteExcluded(t *testing.T) {
 	fstest.CheckItems(t, r.flocal, file2)
 }
 
+// Test with UpdateOlder set
+func TestSyncWithUpdateOlder(t *testing.T) {
+	r := NewRun(t)
+	defer r.Finalise()
+	t2plus := t2.Add(time.Second / 2)
+	t2minus := t2.Add(time.Second / 2)
+	oneF := r.WriteFile("one", "one", t1)
+	twoF := r.WriteFile("two", "two", t3)
+	threeF := r.WriteFile("three", "three", t2)
+	fourF := r.WriteFile("four", "four", t2)
+	fiveF := r.WriteFile("five", "five", t2)
+	fstest.CheckItems(t, r.flocal, oneF, twoF, threeF, fourF, fiveF)
+	oneO := r.WriteObject("one", "ONE", t2)
+	twoO := r.WriteObject("two", "TWO", t2)
+	threeO := r.WriteObject("three", "THREE", t2plus)
+	fourO := r.WriteObject("four", "FOURFOUR", t2minus)
+	fstest.CheckItems(t, r.fremote, oneO, twoO, threeO, fourO)
+
+	fs.Config.UpdateOlder = true
+	oldModifyWindow := fs.Config.ModifyWindow
+	fs.Config.ModifyWindow = fs.ModTimeNotSupported
+	defer func() {
+		fs.Config.UpdateOlder = false
+		fs.Config.ModifyWindow = oldModifyWindow
+	}()
+
+	fs.Stats.ResetCounters()
+	err := fs.Sync(r.fremote, r.flocal)
+	if err != nil {
+		t.Fatalf("Sync failed: %v", err)
+	}
+	fstest.CheckItems(t, r.fremote, oneO, twoF, threeO, fourF, fiveF)
+}
+
 // Test a server side move if possible, or the backup path if not
 func TestServerSideMove(t *testing.T) {
 	r := NewRun(t)