Fix overlapping range passed to BufReadFifo in non-scrolling fifos

On the first read from a nonscrolling fifo, we insert after the buffer
contents (which is just "\n"), and later delete the redundant newline
(582c3c56b (Do not add trailing newline to non-scrolling fifo buffers,
2024-01-28)).  This deletion invalidates inserted ranges passed to
BufReadFifo. Fix that.

The test uses another fifo to pass ranges.  I guess it could use
"ui_out -until" as well but this seems simpler. The test script needs
a fd but 3 and 4 are already taken so use 5.  I didn't find a portable
way to check if it's already taken.

Fixes #5255

0 files changed, 0 insertions, 0 deletions