docs: Removed ambiguity from copy command docs

Switched from talking about "unchanged" files to "identical" files.

I found out the hard way that the rclone copy will overwrite newer files.
Looking at posts in the rclone forum, this is a common experience.

The docs for copy have referred to "unchanged" files.
This is ambiguous because it intuitively introduces a sense
of chronology, but chronology is irrelevant.
Rclone only "cares" about difference, not change.

cmd/copy/copy.go

@@ -23,12 +23,12 @@ func init() {
 
 var commandDefinition = &cobra.Command{
 	Use:   "copy source:path dest:path",
-	Short: `Copy files from source to dest, skipping already copied.`,
+	Short: `Copy files from source to dest, skipping identical files.`,
 	// Note: "|" will be replaced by backticks below
 	Long: strings.ReplaceAll(`
-Copy the source to the destination.  Doesn't transfer
+Copy the source to the destination.  Does not transfer files that are
-unchanged files, testing by size and modification time or
+identical on source and destination, testing by size and modification
-MD5SUM.  Doesn't delete files from the destination.
+time or MD5SUM.  Doesn't delete files from the destination.
 
 Note that it is always the contents of the directory that is synced,
 not the directory so when source:path is a directory, it's the

cmd/copyto/copyto.go

@@ -15,7 +15,7 @@ func init() {
 
 var commandDefinition = &cobra.Command{
 	Use:   "copyto source:path dest:path",
-	Short: `Copy files from source to dest, skipping already copied.`,
+	Short: `Copy files from source to dest, skipping identical files.`,
 	Long: `
 If source:path is a file or directory then it copies it to a file or
 directory named dest:path.
@@ -39,9 +39,9 @@ This will:
         copy it to dst, overwriting existing files if they exist
         see copy command for full details
 
-This doesn't transfer unchanged files, testing by size and
+This doesn't transfer files that are identical on src and dst, testing
-modification time or MD5SUM.  It doesn't delete files from the
+by size and modification time or MD5SUM.  It doesn't delete files from
-destination.
+the destination.
 
 **Note**: Use the ` + "`-P`" + `/` + "`--progress`" + ` flag to view real-time transfer statistics
 `,

cmd/moveto/moveto.go

@@ -39,9 +39,9 @@ This will:
         move it to dst, overwriting existing files if they exist
         see move command for full details
 
-This doesn't transfer unchanged files, testing by size and
+This doesn't transfer files that are identical on src and dst, testing
-modification time or MD5SUM.  src will be deleted on successful
+by size and modification time or MD5SUM.  src will be deleted on
-transfer.
+successful transfer.
 
 **Important**: Since this can cause data loss, test first with the
 ` + "`--dry-run` or the `--interactive`/`-i`" + ` flag.

cmd/sync/sync.go

@@ -25,10 +25,10 @@ var commandDefinition = &cobra.Command{
 	Short: `Make source and dest identical, modifying destination only.`,
 	Long: `
 Sync the source to the destination, changing the destination
-only.  Doesn't transfer unchanged files, testing by size and
+only.  Doesn't transfer files that are identical on source and
-modification time or MD5SUM.  Destination is updated to match
+destination, testing by size and modification time or MD5SUM.
-source, including deleting files if necessary (except duplicate
+Destination is updated to match source, including deleting files
-objects, see below).
+if necessary (except duplicate objects, see below).
 
 **Important**: Since this can cause data loss, test first with the
 ` + "`--dry-run` or the `--interactive`/`-i`" + ` flag.