With-Editor tries very hard to locate a suitable
executable, and then sets option
accordingly. In very rare cases this fails. When it does fail, then
the most likely reason is that someone found yet another way to
package Emacs (most likely on macOS) without putting the executable on
$PATH, and we have to add another kludge to find it anyway.
If you are having problems using
with-editor, e.g. you cannot commit
in Magit, then please open a new issue at
https://github.com/magit/with-editor/issues and provide information
about your Emacs installation. Most importantly how did you install
Emacs and what is the output of
M-x with-editor-debug RET.