feat: treat non-seekable files as pipes (#2309)

Previously, attempting to read from a pipe would result in an error:
'not a regular file', disallowing use of files like /dev/stdin or
/dev/fd/3, named fifos, sockets, etc.

The tools already understand how to (try to) read from non-regular
files, so this change attempts to do so when the input is not seek-able
(the "regular file" capability that's in use here).

Additionally, this adds a test for the new behavior using a bash
herestring and process substitution (the latter of which shows up in
argv as something like `/dev/fd/NN`). Since bash isn't commonly
installed on Windows, this change also introduces a new capability to
filter tests to specific platforms (sorry).

0 files changed, 0 insertions, 0 deletions