t7527: add case-insensitve test for FSMonitor
The FSMonitor client code trusts the spelling of the pathnames in the FSEvents received from the FSMonitor daemon. On case-insensitive file systems, these OBSERVED pathnames may be spelled differently than the EXPECTED pathnames listed in the .git/index. This causes a miss when using `index_name_pos()` which expects the given case to be correct. When this happens, the FSMonitor client code does not update the state of the CE_FSMONITOR_VALID bit when refreshing the index (and before starting to scan the worktree). This results in modified files NOT being reported by `git status` when there is a discrepancy in the case-spelling of a tracked file's pathname. This commit contains a (rather contrived) test case to demonstrate this. A later commit in this series will update the FSMonitor client code to recognize these discrepancies and update the CE_ bit accordingly. Signed-off-by: Jeff Hostetler <jeffhostetler@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>