In commit 509a624 (filter-repo: fix issue with pruning of empty commits,
2019-10-03), it was noted that when the first parent is pruned away,
then we need to generate a corrected list of file changes relative to
the new first parent. Unfortunately, we did not apply our set of file
filters to that new list of file changes, causing us to possibly
introduce many unwanted files from the second parent into the history.
The testcase added at the time was rather lax and totally missed this
problem (which possibly exacerbated the original bug being fixed rather
than helping). Tighten the testcase, and fix the error by filtering the
generated list of file changes.
Signed-off-by: Elijah Newren <newren@gmail.com>
a9a93d9d83