When opening a nonexistent file with nano, it likely consists of only a
name without any path component, and thus without any slash. So when a
file regex checks for a slash, it should check also for start-of-string.
This fixes https://savannah.gnu.org/bugs/?65591.
Problem existed for the Makefile since version 2.9.8, commit 22663f8a,
and for .profile since version 3.0, commit 4a268678 (but earlier, nano
did not recognize .profile files at all).
c02aec557c