fs/config/configflags: fix --compare-dest and --copy-dest help strings

from rsync manual:

--compare-dest=DIR
    This option instructs rsync to use DIR on the destination machine as an
    additional hierarchy to compare destination files against doing transfers
    (if the files are missing in the destination directory). If a file is found
    in DIR that is identical to the sender's file, the file will NOT be
    transferred to the destination directory. This is useful for creating
    a sparse backup of just files that have changed from an earlier backup.

--copy-dest=DIR
    This option behaves like --compare-dest, but rsync will also copy unchanged
     files found in DIR to the destination directory using a local copy.
      This is useful for doing transfers to a new destination while leaving
       existing files intact, and then doing a flash-cutover when all files
        have been successfully transferred.

fs/config/configflags/configflags.go

@@ -69,8 +69,8 @@ func AddFlags(flagSet *pflag.FlagSet) {
 	flags.BoolVarP(flagSet, &fs.Config.IgnoreCaseSync, "ignore-case-sync", "", fs.Config.IgnoreCaseSync, "Ignore case when synchronizing")
 	flags.BoolVarP(flagSet, &fs.Config.NoTraverse, "no-traverse", "", fs.Config.NoTraverse, "Don't traverse destination file system on copy.")
 	flags.BoolVarP(flagSet, &fs.Config.NoUpdateModTime, "no-update-modtime", "", fs.Config.NoUpdateModTime, "Don't update destination mod-time if files identical.")
-	flags.StringVarP(flagSet, &fs.Config.CompareDest, "compare-dest", "", fs.Config.CompareDest, "use DIR to server side copy flies from.")
-	flags.StringVarP(flagSet, &fs.Config.CopyDest, "copy-dest", "", fs.Config.CopyDest, "Compare dest to DIR also.")
+	flags.StringVarP(flagSet, &fs.Config.CompareDest, "compare-dest", "", fs.Config.CompareDest, "Include additional server-side path during comparison.")
+	flags.StringVarP(flagSet, &fs.Config.CopyDest, "copy-dest", "", fs.Config.CopyDest, "Implies --compare-dest but also copies files from path into destination.")
 	flags.StringVarP(flagSet, &fs.Config.BackupDir, "backup-dir", "", fs.Config.BackupDir, "Make backups into hierarchy based in DIR.")
 	flags.StringVarP(flagSet, &fs.Config.Suffix, "suffix", "", fs.Config.Suffix, "Suffix to add to changed files.")
 	flags.BoolVarP(flagSet, &fs.Config.SuffixKeepExtension, "suffix-keep-extension", "", fs.Config.SuffixKeepExtension, "Preserve the extension when using --suffix.")