Merge branch 'origin/master'

For a short while, we had two tracks: the `master` one, based on
v2.19.2, and the `rebase-to-v2.20.0-rc<N>` one, following the -rc
versions of v2.20.0.

Since we forward-ported all changes from `master` to the -rc track (or
backported them in the other direction), at this point we have all of
`origin/master` already, and can continue the merging rebase to v2.20.0
based on the `rebase-to-v2.20.0-rc<N>` track (which has a lot of the
merge conflicts resolved already).

So let's just merge in the commit history of `master`, without changing
the tree (i.e. with `-s ours`, just like the fake merge starting the
merging rebase). That way, the new `master` will fast-forward from the
old `master`.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho