monline

I don't know about earlier releases, but ICS has a bash shell in /system/bin. If you start a shell through ADB (eg. ./adb shell), it'll start /system/bin/sh as a shell which is a symlink to bash. Unfortunately ADB does not add the -l option to the shell's commandline, thus the shell will not be a login shell and it'll not look for _any_ configuration files.

The good news is that you just have to execute the shell again with the -l switch (either sh -l or bash -l) and it'll read/execute a few config files. I've compiled strace to be able to get the list of actual pathes that bash looks in for config files.
These locations are:

Of course by default there's no $HOME variable defined. In that case bash looks in the root directory (the first four entries in the above list). But if you do set a $HOME, bash will look there (and not in the root dir).

To make your life easy, you could place your shell/environment settings in /etc/profile (aka. /system/etc/profile). And while you're at it, don't forget to set $HOME and $USER too. Both might come handy.

P.S.: to automate the full process, you could replace the /system/bin/sh symlink with a simple shell script.
Eg.
Or ...

P.S.2: the problem with bash was discussed quite extensively in a topic at xda-developers.com (although nobody got to the results that I've explained above), but unfortunately newly registered users are not allowed to comment in development related forums, so I couldn't share my findings there.

P.S.3: if for some reason your /system/bin/bash shell became setuid root (eg. RootLogger does that), then the bash started by ADB won't load /etc/profile because at this time the shell runs as the "shell" user and the config file is owned by root. However if right after ./adb shell you start a su -s /system/bin/bash -l root login shell, it'll load the config file's contents. The second variant of my /system/bin/sh replacement suggestions works around this problem too.