There is a problem when a user job adds too many dependency jars in their command line. The HADOOP_CLASSPATH part can be addressed, including using wildcards (*). But the same cannot be done with the -libjars argument. Today it takes only fully specified file paths.
We may want to consider supporting wildcards as a way to help users in this situation. The idea is to handle it the same way the JVM does it: * expands to the list of jars in that directory. It does not traverse into any child directory.
Also, it probably would be a good idea to do it only for libjars (i.e. don't do it for -files and -archives).