~/mongo $ cat dump/test/caf%C3%A9s.bson | ./mongodb-4.2.0-rc2/bin/mongorestore
-u kayadmin -p abc123 --authenticationDatabase=admin --db test --collection
cafes -
2019-07-08T14:28:52.937-0400	the --db and --collection args should only be used
when restoring from a BSON file. Other uses are deprecated and will not exist in
the future; use --nsInclude instead
2019-07-08T14:28:52.938-0400	setting up a collection to be read from standard
input
2019-07-08T14:28:52.938-0400	restoring to existing collection test.cafes without
dropping
2019-07-08T14:28:52.938-0400	restoring test.cafes from -
2019-07-08T14:28:53.002-0400	no indexes to restore
2019-07-08T14:28:53.002-0400	finished restoring test.cafes (2 documents, 0
failures)
2019-07-08T14:28:53.002-0400	2 document(s) restored successfully. 0 document(s)
failed to restore.

But, the following examples don't seem to work:

cat dump/test/caf%C3%A9s.bson | ./mongodb-4.2.0-rc2/bin/mongorestore -u kayadmin
-p abc123 --authenticationDatabase=admin --nsInclude test.cafe -
2019-07-08T14:42:35.814-0400	Failed: cannot restore from stdin without a
specified collection
2019-07-08T14:42:35.815-0400	0 document(s) restored successfully. 0 document(s)
failed to restore.


 
~/mongo $ ./mongodb-4.2.0-rc2/bin/mongodump --port 27018 -u kayadmin -p abc123
--authenticationDatabase=admin --db test --collection cafés |
./mongodb-4.2.0-rc2/bin/mongorestore -u kayadmin --authenticationDatabase=admin
-p abc123 --db=test --collection cafes -  
2019-07-08T14:25:15.159-0400	the --db and --collection args should only be used
when restoring from a BSON file. Other uses are deprecated and will not exist in
the future; use --nsInclude instead
2019-07-08T14:25:15.159-0400	setting up a collection to be read from standard
input
2019-07-08T14:25:15.159-0400	writing test.cafés to 
2019-07-08T14:25:15.160-0400	done dumping test.cafés (2 documents)
2019-07-08T14:25:15.194-0400	restoring test.cafes from -
2019-07-08T14:25:15.265-0400	no indexes to restore
2019-07-08T14:25:15.265-0400	finished restoring test.cafes (0 documents, 0
failures)
2019-07-08T14:25:15.265-0400	0 document(s) restored successfully. 0 document(s)
failed to restore.


~/mongo $ ./mongodb-4.2.0-rc2/bin/mongodump --port 27018 -u kayadmin -p abc123
--authenticationDatabase=admin --db test --collection cafés |
./mongodb-4.2.0-rc2/bin/mongorestore -u kayadmin -p abc123
--authenticationDatabase=admin --nsInclude test.cafés - 
2019-07-08T14:25:32.192-0400	Failed: cannot restore from stdin without a
specified collection
2019-07-08T14:25:32.192-0400	0 document(s) restored successfully. 0 document(s)
failed to restore.
2019-07-08T14:25:32.193-0400	writing test.cafés to 
2019-07-08T14:25:32.194-0400	done dumping test.cafés (2 documents)