Merge branch 'mk/show-s-no-extra-blank-line-for-merges' into maint

"git show -s" (i.e. show log message only) used to incorrectly emit
an extra blank line after a merge commit.

* mk/show-s-no-extra-blank-line-for-merges:
git-show: fix 'git show -s' to not add extra terminator after merge commit

diff --cc combine-diff.c
Simple merge