Suppress shell session exit messages on macOS

[dscorbett]

Fixes #91.

[mosabua]

That seems fine to me .. although is it really only the Apple terminal that is affected .. what it other console like iterm is used?

[dscorbett]

On macOS, /etc/bashrc ends with [ -r "/etc/bashrc_$TERM_PROGRAM" ] && . "/etc/bashrc_$TERM_PROGRAM". In iTerm and iTerm2, TERM_PROGRAM is iTerm.app. Only /etc/bashrc_Apple_Terminal exists by default, which is the file responsible for these session termination messages. I checked for specifically [ "$TERM_PROGRAM" = "Apple_Terminal" ] because that is the only terminal where I could reproduce the problem. On the other hand, I suppose it is safe enough to (re)define shell_session_save unconditionally. I’ll push that change shortly.

[mosabua]

Does that have any negative effects on Linux ?

[dscorbett]

I tried it on Linux without any difference in behavior. shell_session_save is a macOS thing; I don’t think it is used on Linux. Even if it is, its effect is highly limited in scope, since _realpath is only ever called in a subshell.

[mosabua]

Excellent .. I am good with this then. @juven ?