Merge branch 'ds/maintenance-on-windows-fix'

Windows updates.

* ds/maintenance-on-windows-fix:
  git maintenance: avoid console window in scheduled tasks on Windows
  win32: add a helper to run `git.exe` without a foreground window

diff --cc Makefile
Simple merge

diff --cc builtin/gc.c
Simple merge

diff --cc contrib/buildsystems/CMakeLists.txt
Simple merge