Start the merging-rebase to v2.26.0

When merging the PR that replaces the Azure Pipeline with a GitHub
workflow, we had to resolve merge conflicts (actually, those merge
conflicts were resolved _in_ the PR's commits). Part of the merge
conflicts come from our README modifications, part of them come from our
BusyBox patches.

To avoid having to resolve them every time the `ever-green.sh` script is
used by the automated builds that rebase Git for Windows' `master` onto
Git's four integration branches, let's reorder the patches (and modify
some) to still yield the exact same tree, but with a cleaner commit
history.

This commit starts the rebase of a6da52b to adf6396efeb4

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>