sequencer: strip CR from the todo script

sequencer: strip CR from the todo script

It is not unheard of that editors on Windows write CR/LF even if the
file originally had only LF. This is particularly awkward for exec lines
of a rebase -i todo sheet. Take for example the insn "exec echo": The
shell script parser splits at the LF and leaves the CR attached to
"echo", which leads to the unknown command "echo\r".

Work around that by stripping CR when reading the todo commands, as we
already do for LF.

This happens to fix t9903.14 and .15 in MSYS1 environments (with the
rebase--helper patches based on this patch series): the todo script
constructed in such a setup contains CR/LF thanks to MSYS1 runtime's
cleverness.

Based on a report and a patch by Johannes Sixt.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>