Expand path variables for sync destination (#18)

Expand path variables for sync destination

Running commands like cdc_rsync C:\assets\* host:~/assets -vr would create a directory called ~assets. This CL expands path variables properly.

cdc_rsync_server/cdc_rsync_server.cc

@@ -303,7 +303,7 @@ absl::Status CdcRsyncServer::HandleSetOptions() {
   existing_ = request.existing();
   copy_dest_ = request.copy_dest();
 
-  // (internal): Support \ instead of / in destination folders.
+  // Support \ instead of / in destination folders.
   path::FixPathSeparators(&destination_);
   path::EnsureEndsWithPathSeparator(&destination_);
   if (!copy_dest_.empty()) {
@@ -311,6 +311,13 @@ absl::Status CdcRsyncServer::HandleSetOptions() {
     path::EnsureEndsWithPathSeparator(&copy_dest_);
   }
 
+  // Expand e.g. ~.
+  status = path::ExpandPathVariables(&destination_);
+  if (!status.ok()) {
+    return WrapStatus(status, "Failed to expand destination '%s'",
+                      destination_);
+  }
+
   assert(path_filter_.IsEmpty());
   for (int n = 0; n < request.filter_rules_size(); ++n) {
     std::string fixed_pattern = request.filter_rules(n).pattern();