Stuff worth explaining
This file provides prompt_command function that is executed by the shell just before displaying PS1 (which the function sets). The result is a colored shell prompt.
Note that the clock is not real-time. It updates after your shell command finishes (e.g. after you press enter). That's sufficient if you want to know how long your db backup took, for example.
There are two implementations of mercurial prompt: using a separate mercurial extension hg-prompt, and a fallback implementation in pure bash.
The screenshot shows the former in action:
Pure bash implementation currently lags behind in features.
Mercurial and Git support is disabled for root, thus two colored dashes.
This file contains aliases. Currently, the only alias that is not exactly self-explanatory is whatsopen. In short, it's an alternative to sockstat from FreeBSD. It shows listening (TCP) applications, like netstat -ntlp, but with a handy difference. It additionally shows users, so instead of this:
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 127.0.0.1:5984 0.0.0.0:* LISTEN 30617/beam.smp
you get this:
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME beam.smp 30617 couchdb 16u IPv4 7652760 0t0 TCP 127.0.0.1:5984 (LISTEN)
See? It's much easier to guess what beam.smp is when you know couchdb owns it. And it's much, much easier to understand what python2 is doing there when its owner is my-django-site-user or something.