Merge branch 'pw/rebase-i-squash-number-fix'

When "git rebase -i" is told to squash two or more commits into
one, it labeled the log message for each commit with its number.
It correctly called the first one "1st commit", but the next one
was "commit #1", which was off-by-one.  This has been corrected.

* pw/rebase-i-squash-number-fix:
rebase -i: fix numbering in squash message

diff --cc sequencer.c
Simple merge

diff --cc t/t3418-rebase-continue.sh
Simple merge