Subject: Backports from master.

Use ``git cherry-pick -x SHA1''.

The ChangeLog hunk (which failed to apply) goes into ChangeLog.SHA1.

After ``tg update'' (and possibly dealing with merge conflicts), check which
can be removed:

    $ for c in ChangeLog.???*; do sha1=$(expr "$c" : 'ChangeLog.\(.*\)') && git rev-list HEAD | grep -q "$sha1" && echo "$sha1 has been merged"; done

Check this, and remove the ChangeLog.SHA1.

If there are no backports, ``git diff baseline'' must only show the .top*
files on t/master_backports.