This commit fixes an issue with themes on OS X which are sometimes
left in a partially broken environment with missing dependencies.
When a `BASH_IT_THEME` is active on OS X and has a
dynamic `PROMPT_COMMAND` which is not exported, and such
`PROMPT_COMMAND` is backed by shell functions which are not
exported either, and at the same time the theme is not
OS-X-aware (regarding `update_terminal_cwd`), and the
user launches a (non-login) interactive subshell from
the OS X Terminal, a `command not found` appears on every
command invocation.
The issue is caused by a regression in PR #514, which attempts to
inject `update_terminal_cwd` into the prompt. As a side effect, it
also escalates the exportedness of `PROMPT_COMMAND` while the
theme-specific backing functions (which power the dynamic prompt)
remain unexported.
The subshell cannot recover from this partially broken environment
because unlike in Linux, Bash-it on OS X is not invoked for non-login
subshells. The dependencies remain broken which leads to the error.
The fix is to preserve `PROMPT_COMMAND`’s exportedness on OS X,
leaving the individual theme responsible for consistently
exporting either all or nothing of its environment.
3f05d6b3fd