Problem

The docs on mongostat say:

--host <hostname><:port>
...
To connect to a replica set, you can specify the replica set seed name, and a seed list of set members, in the following format:

<replica_set_name>/<hostname1><:port>,<hostname2:<port>,...

This does not work. Mongostat does not accept a replica set name + seed list in the usual connection string format.

Example

$ mongostat --host replset/capslock.local:27017,capslock.local:27018,capslock.local:27019

                            	insert  query update delete getmore command flushes mapped  vsize    res faults  locked db idx miss %     qr|qw   ar|aw  netIn netOut  conn     set repl       time 
        capslock.local:27018	    *0     *0     *0     *0       0     3|0       0   336m  3.15g     3m      0 local:0.0%          0       0|0     0|0   328b     3k     3 replset  SEC   09:54:24 
        capslock.local:27019	    *0     *0     *0     *0       0     3|0       0   336m  3.15g     3m      0 local:0.0%          0       0|0     0|0   328b     3k     3 replset  SEC   09:54:24 
replset/capslock.local:27017	socket exception [CONNECT_ERROR] for replset/capslock.local:27017

Reason

The runMany() function (see src/tools/stat.cpp:430) splits the host parameter just by "," with StringSplitter.

Expected behavior

When specifying a connection string with replica set name and seed list, it should properly connect to one of the seed nodes and discover the rest of the replica set (similar to --discover). If we don't want to duplicate this functionality, we should at least ignore the replica set name (i.e. strip it off the string before), then show the provided hosts in the seed list. But then we need to also change the docs to point to --discover instead for full replica set display.