[PATCH v2] t0021: make sure clean filter runs

In t0021.15 one of the things we are checking is that the clean filter is run when checking out empty-branch. The clean filter needs to be run to make sure there are no modifications on the file system for the test.r file, and thus it isn't dangerous to overwrite it.

However in the current test setup it is not always necessary to run the clean filter, and thus the test sometimes fails, as debug.log isn't written.

This happens when test.r has an older mtime than the index itself. That mtime is also recorded as stat data for test.r in the index, and based on the heuristic we're using for index entries, git correctly assumes this file is up-to-date.

Usually this test succeeds because the mtime of test.r is the same as the mtime of the index. In this case test.r is racily clean, so git actually checks the contents, for which the clean filter is run.

Fix the test by updating the mtime of test.r, so git is forced to check the contents of the file, and the clean filter is run as the test expects.

Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
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v2 adds the comment as suggested by Szeder.

Junio: I saw this is marked as "merged to 'next'" in the What's
cooking, so if it got merged already I'm fine with just keeping v1,
but otherwise I think adding the comment would be nice.

 t/t0021-conversion.sh | 3 +++
 1 file changed, 3 insertions(+)