Start the merging-rebase to junio/maint

This commit starts the rebase of d3c269f to 49981d8

In keeping with the fine tradition of making major changes and
immediately going offline for a few weeks, this merging rebase updates
Git for Windows' master branch to the current `maint` of upstream Git.

Please note that we rease to maint instead of master because it is
very likely that v2.10.1 will be released before v2.11.0.

We use this opportunity to update the 'jh/status-v2-porcelain',
'cat-file-filters' and 'interactive-rebase' branches to the latest
iterations.

While at it, we also squash the GitHub issue template patches into
a single one.

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

Author: dscho