change macOS /bin/sh from /bin/bash to /bin/dash

gistfile1.txt

sh is a POSIX-compliant command interpreter (shell).  It is implemented
by re-execing as either bash(1), dash(1), or zsh(1) as determined by the
symbolic link located at /private/var/select/sh.  If
/private/var/select/sh does not exist or does not point to a valid shell,
sh will use one of the supported shells.
     
$ ls -l /private/var/select
total 0
lrwxr-xr-x 1 root wheel 9 Jan 23 09:47 sh -> /bin/dash
lrwxr-xr-x 1 root wheel 9 Dec  2 06:37 sh.ori -> /bin/bash