Merge branch 'fs/ssh-signing-key-lifetime'

"git merge $signed_tag" started to drop the tag message from the
default merge message it uses by accident, which has been corrected.

* fs/ssh-signing-key-lifetime:
  fmt-merge-msg: prevent use-after-free with signed tags

diff --cc fmt-merge-msg.c
Simple merge

diff --cc t/t6200-fmt-merge-msg.sh
Simple merge