operations: implement --partial-suffix to control extension of temporary file names

docs/content/docs.md

@@ -1278,8 +1278,9 @@ flag set) such as:
 - sftp
 
 Without `--inplace` (the default) rclone will first upload to a
-temporary file with an extension like this where `XXXXXX` represents a
-random string.
+temporary file with an extension like this, where `XXXXXX` represents a
+random string and `.partial` is [--partial-suffix](#partial-suffix) value
+(`.partial` by default).
 
     original-file-name.XXXXXX.partial
 
@@ -1726,6 +1727,15 @@ If you want perfect ordering then you will need to specify
 [--check-first](#check-first) which will find all the files which need
 transferring first before transferring any.
 
+### --partial-suffix {#partial-suffix}
+
+When [--inplace](#inplace) is not used, it causes rclone to use
+the `--partial-suffix` as suffix for temporary files.
+
+Suffix length limit is 16 characters.
+
+The default is `.partial`.
+
 ### --password-command SpaceSepList ###
 
 This flag supplies a program which should supply the config password

fs/config.go

@@ -148,6 +148,7 @@ type ConfigInfo struct {
 	TerminalColorMode          TerminalColorMode
 	DefaultTime                Time // time that directories with no time should display
 	Inplace                    bool // Download directly to destination file instead of atomic download to temp/rename
+	PartialSuffix              string
 }
 
 // NewConfig creates a new config with everything set to the default
@@ -192,6 +193,7 @@ func NewConfig() *ConfigInfo {
 	c.FsCacheExpireInterval = 60 * time.Second
 	c.KvLockTime = 1 * time.Second
 	c.DefaultTime = Time(time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC))
+	c.PartialSuffix = ".partial"
 
 	// Perform a simple check for debug flags to enable debug logging during the flag initialization
 	for argIndex, arg := range os.Args {

fs/config/configflags/configflags.go

@@ -38,6 +38,7 @@ var (
 	downloadHeaders []string
 	headers         []string
 	metadataSet     []string
+	partialSuffix   string
 )
 
 // AddFlags adds the non filing system specific flags to the command
@@ -148,6 +149,7 @@ func AddFlags(ci *fs.ConfigInfo, flagSet *pflag.FlagSet) {
 	flags.FVarP(flagSet, &ci.TerminalColorMode, "color", "", "When to show colors (and other ANSI codes) AUTO|NEVER|ALWAYS", "Config")
 	flags.FVarP(flagSet, &ci.DefaultTime, "default-time", "", "Time to show if modtime is unknown for files and directories", "Config,Listing")
 	flags.BoolVarP(flagSet, &ci.Inplace, "inplace", "", ci.Inplace, "Download directly to destination file instead of atomic download to temp/rename", "Copy")
+	flags.StringVarP(flagSet, &partialSuffix, "partial-suffix", "", ci.PartialSuffix, "Add partial-suffix to temporary file name when --inplace is not used", "Copy")
 }
 
 // ParseHeaders converts the strings passed in via the header flags into HTTPOptions
@@ -322,6 +324,11 @@ func SetFlags(ci *fs.ConfigInfo) {
 	multiThreadStreamsFlag := pflag.Lookup("multi-thread-streams")
 	ci.MultiThreadSet = multiThreadStreamsFlag != nil && multiThreadStreamsFlag.Changed
 
+	if len(partialSuffix) > 16 {
+		log.Fatalf("--partial-suffix: Expecting suffix length not greater than %d but got %d", 16, len(partialSuffix))
+	}
+	ci.PartialSuffix = partialSuffix
+
 	// Make sure some values are > 0
 	nonZero := func(pi *int) {
 		if *pi <= 0 {

fs/operations/operations.go

@@ -359,9 +359,13 @@ func Copy(ctx context.Context, f fs.Fs, dst fs.Object, remote string, src fs.Obj
 		remotePartial = remote
 	)
 	if !ci.Inplace && f.Features().Move != nil && f.Features().PartialUploads && !strings.HasSuffix(remote, ".rclonelink") {
+		if len(ci.PartialSuffix) > 16 {
+			return nil, fmt.Errorf("expecting length of --partial-suffix to be not greater than %d but got %d", 16, len(ci.PartialSuffix))
+		}
+
 		// Avoid making the leaf name longer if it's already lengthy to avoid
 		// trouble with file name length limits.
-		suffix := "." + random.String(8) + ".partial"
+		suffix := "." + random.String(8) + ci.PartialSuffix
 		base := path.Base(remotePartial)
 		if len(base) > 100 {
 			remotePartial = remotePartial[:len(remotePartial)-len(suffix)] + suffix