command line arguments

Nobody has claimed this yet.

The original Lua hostlist has a slightly different set of command line arguments. This is taken from the help text on quartz (`hostlist -h`):

```
Usage: hostlist [OPTION]... [HOSTLIST]...

-h, --help Display this message.
-q, --quiet Quiet output (exit non-zero if empty hostlist).
-d, --delimiters=S Set output delimiter (default = ",")
-c, --count Print the number of hosts
-s, --size=N Output at most N hosts (-N for last N hosts)
-e, --expand Expand host list instead of collapsing
-n, --nth=N Output the host at index N (-N to index from end)
-u, --union Union of all HOSTLIST arguments
-m, --minus Subtract all HOSTLIST args from first HOSTLIST
-i, --intersection Intersection of all HOSTLIST args
-x, --exclude Exclude all HOSTLIST args from first HOSTLIST
-X, --xor Symmetric difference of all HOSTLIST args
-R, --remove=N Remove only N occurrences of args from HOSTLIST
-S, --sort Return sorted HOSTLIST
-f, --filter=CODE Map Lua CODE over all hosts in result HOSTLIST
-F, --find=HOST Output position of HOST in result HOSTLIST
(exits non-zero if host not found)

An arbitrary number of HOSTLIST arguments are supported for all
operations. The default operation is to concatenate all HOSTLIST args.
```

Note that capital S is sort, lowercase s is size.

We should either maintain identical commands as lua-hostlist or clearly document where py-hostlist is different.

Start by comparing py-hostlist's command-line help and behavior with the lua-hostlist help text shown from quartz. Identify which options differ, then confirm whether the intended outcome is command parity or documentation of differences; done means the chosen behavior or documentation covers the listed arguments, including the lowercase and uppercase size/sort distinction.

Written by the indexing model from the issue text.