On Windows, there are two kinds of executables, console ones and
non-console ones. Git's executables are all console ones.

When launching the former e.g. in a scheduled task, a CMD window pops
up. This is not what we want for the tasks installed via the `git
maintenance` command.

To work around this, let's introduce `headless-git.exe`, which is a
non-console program that does _not_ pop up any window. All it does is to
re-launch `git.exe`, suppressing that console window, passing through
all command-line arguments as-are.

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

We just introduced a helper to avoid showing a console window when the
scheduled task runs `git.exe`. Let's actually use it.

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

This check verifies that the ODB matches what we supplied, but there are
some subtleties around Windows path names that can cause inexact matches
to be logically the same. Since this check is really intended only for
debugging and development purposes, let's remove it for now as a quick
workaround.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>