set $ATHENA_USER everywhere

[geofft]

There are not-particularly-pathological circumstances under which $ATHENA_USER is unset for an account it is ordinarily set for. Since it's easier to use a single environment variable where we want an Athena username instead of making sure everything is capable of understanding the ${ATHENA_USER:-$USER} syntax (cf. #413), we should consider being more aggressive about setting $ATHENA_USER, either by doing it in different dotfiles or in PAM somehow.

(Besides, as #553 points out, ${ATHENA_USER:-$USER} is sometimes wrong; there are local accounts that don't actually have an Athena user that corresponds to them.)

As a specific example of when this might fail to be set:

dr-wily:~ geofft$ ssh kid 'echo $ATHENA_USER'

dr-wily:~ geofft$ ssh kid
[...]
kid-icarus:~ geofft$ echo $ATHENA_USER
geofft

So, for instance, X-forwarded applications without a shell around them won't see $ATHENA_USER (consider ssh kid thunderbird for instance), but they will if I start them from a shell, which is confusingly inconsistent.

[broder]

The reason we use ${ATHENA_USER:-$USER} everywhere is that we don't and shouldn't require you to have bash-config/tcsh-config installed in order for any of our config packages to work.