Problem:
`nvim -u NONE -d <(xxd one) <(xxd two)` has weird behavior.
Process substitution `<(...)` is a pipe and not a seekable file.
Test case:
cat /dev/random | head -c 10240 > one
cp one two
cat /dev/random | head -c 10240 >> two
nvim -u NONE -d <(xxd one) <(xxd two)
Solution:
Workaround the issue by skipping `nvim.difftool` if the 2 args are not
directories; fall-through to the builtin diff handling.
Signed-off-by: Tomas Slusny <slusnucky@gmail.com>
(cherry picked from commit 2fd2361a9d)
ed7acd1391
