Merge branch 'jc/maint-sane-execvp-notdir'

"git foo" errored out with "Not a directory" when the user had a non
directory on $PATH, and worse yet it masked an alias "foo" to run.

* jc/maint-sane-execvp-notdir:
sane_execvp(): ignore non-directory on $PATH

diff --cc run-command.c
Simple merge