Bash shell detection was originally disabled in #1823 due to problems
with /bin/bash on macOS.
Apple distributes their own patched version of Bash 3.2 on macOS that
disables the POSIX-style $ENV-based startup path:
e5397a7e74/bash-3.2/shell.c (L1112-L1114)
This means we're unable to perform our automatic shell integration
sequence in this specific environment. Standard Bash 3.2 works fine.
Knowing this, we can re-enable bash shell detection by default unless
we're running "/bin/bash" on Darwin. We can safely assume that's the
unsupported Bash executable because /bin is non-writable on modern macOS
installations due to System Integrity Protection.
macOS users can either manually source our shell integration script
(which otherwise works fine with Apple's Bash) or install a standard
version of Bash from Homebrew or elsewhere.
For now, bash integration must be explicitly enabled (by setting
`shell-integration = bash`). Our automatic shell integration requires
bash version 4 or later, and systems like macOS continue to ship bash
version 3 by default. This approach avoids the cost of performing a
runtime version check.
Fish automatic integration taken as an example.
Just like fish, Elvish checks `XDG_DATA_DIRS` for its modules.
Thus, Fish integration in zig is reused, and integration in
Elvish now removes `GHOSTTY_FISH_XDG_DIR` environment variable
on launch.
