Fix intermittent test failures

The testReCecksumming test succeeded only by mistake, and only most
of the time: the checksummer would see that there is a .checksums
file with cached checksums, see that the timestamps matched, and
would fail to re-checksum the files.

Test properly that files are re-checksummed, and make sure that the
checksummer has no .checksums file for a reason to procrastinate.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Use Checksummer correctly in the UpdaterTest

By removing the file containing its cached checksums before running it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Let Maven 'install' ij-updater-core before running the integration test

To allow for "mvn verify" to pass, ij-updater-core needs to be found by
the integration test even if it is not locally installed (and neither
available from Maven Central...). Therefore, we need to run the
'install' goal of the invoker plugin.

While at it, log a bit more verbosely.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Another microscoff time tax

In instances where still-locked files are about to become unused,
Windows makes this a problem: it refuses to delete them. Typically you
work around this by calling File#deleteOnExit. But if you have to delete
directories recursively, no such easy way is available. So we have to
make it available.

I wish we would get something back in return for having to spend so much
time to work around design flaws in Windows for a change.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Use the newly introduced deleteRecursivelyAtLeastOnExit in test cleanups

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge branch 'windows-fix'

This fixes the test breakages on Windows pointed out by Jenkins'
ImageJ-windows job which were introduced by the integration tests for
the uploader auto-install feature of the updater.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge branch 'fix-updater-tests'

This branch fixes the intermittent test failures due to sloppy use of
the Checksummer in the updater tests.

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