b2: Enable mod time syncing - fixes #348

b2/b2.go

@@ -615,7 +615,7 @@ func (f *Fs) Rmdir() error {
 
 // Precision of the remote
 func (f *Fs) Precision() time.Duration {
-	return fs.ModTimeNotSupported
+	return time.Second
 }
 
 // deleteByID deletes a file version given Name and ID

docs/content/b2.md

@@ -96,9 +96,10 @@ The modified time is stored as metadata on the object as
 in the Backblaze standard.  Other tools should be able to use this as
 a modified time.
 
-Modified times are set on upload, read on download and shown in
-listings.  They are not used in syncing as unfortunately B2 doesn't
-have an API method to set them independently of doing an upload.
+Modified times are used in syncing and are fully supported except in
+the case of updating a modification time on an existing object.  In
+this case the object will be uploaded again as B2 doesn't have an API
+method to set the modification time independent of doing an upload.
 
 ### SHA1 checksums ###
 
@@ -124,6 +125,3 @@ the old versions will be deleted.
 Here are [some notes I made on the backblaze
 API](https://gist.github.com/ncw/166dabf352b399f1cc1c) while
 integrating it with rclone which detail the changes I'd like to see.
-With a couple of small tweaks Backblaze could enable rclone to not
-make a temporary copy of files when doing cloud to cloud copies and
-fully support modification times.

docs/content/overview.md

@@ -25,7 +25,7 @@ Here is an overview of the major features of each cloud storage system.
 | Amazon Cloud Drive     | MD5     | No      | Yes              | No              |
 | Microsoft One Drive    | SHA1    | Yes     | Yes              | No              |
 | Hubic                  | MD5     | Yes     | No               | No              |
-| Backblaze B2           | SHA1    | Partial | No               | No              |
+| Backblaze B2           | SHA1    | Yes     | No               | No              |
 | Yandex Disk            | MD5     | Yes     | No               | No              |
 | The local filesystem   | All     | Yes     | Depends          | No              |
 
@@ -49,9 +49,6 @@ default, though the MD5SUM can be checked with the `--checksum` flag.
 All cloud storage systems support some kind of date on the object and
 these will be set when transferring from the cloud storage system.
 
-Backblaze B2 preserves file modification times on files uploaded and
-downloaded, but doesn't use them to decide which objects to sync.
-
 ### Case Insensitive ###
 
 If a cloud storage systems is case sensitive then it is possible to
@@ -78,4 +75,5 @@ systems.
 If a cloud storage system allows duplicate files then it can have two
 objects with the same name.
 
-This confuses rclone greatly when syncing.
+This confuses rclone greatly when syncing - use the `rclone dedupe`
+command to rename or remove duplicates.

fs/operations.go

@@ -146,7 +146,10 @@ func Equal(src, dst Object) bool {
 		// Size and hash the same but mtime different so update the
 		// mtime of the dst object here
 		err := dst.SetModTime(srcModTime)
-		if err != nil {
+		if err == ErrorCantSetModTime {
+			Debug(src, "src and dst identical but can't set mod time without re-uploading")
+			return false
+		} else if err != nil {
 			Stats.Error()
 			ErrorLog(dst, "Failed to read set modification time: %s", err)
 		}

fstest/fstests/fstests.go

@@ -497,7 +497,13 @@ func TestObjectSetModTime(t *testing.T) {
 	skipIfNotOk(t)
 	newModTime := fstest.Time("2011-12-13T14:15:16.999999999Z")
 	obj := findObject(t, file1.Path)
-	obj.SetModTime(newModTime)
+	err := obj.SetModTime(newModTime)
+	if err == fs.ErrorCantSetModTime {
+		t.Log(err)
+		return
+	} else if err != nil {
+		t.Fatal(err)
+	}
 	file1.ModTime = newModTime
 	file1.CheckModTime(t, obj, obj.ModTime(), remote.Precision())
 	// And make a new object and read it from there too