Have touch in test fixture fall back to portable format

For each edge-of-range `touch`, if at first it fails, try it
rounded to the nearest *more extreme* value in seconds, which some
implementations will accept and clip it at or near the most
extreme value in the range that it was going for.

See GitoxideLabs#1491.

Author: EliahKagan

gix-index/tests/fixtures/file_metadata.sh

@@ -1,7 +1,9 @@
 #!/usr/bin/env bash
 set -eu -o pipefail
 
-# The largest-possible date for Ext4, nanos are special there, but ont usually on other filesystems
-touch -d "2446-05-10 22:38:55.111111111" future
-# The smallest-possible date for Ext4, nanos are special there, but ont usually on other filesystems
-touch -d "1901-12-13 20:45:52.222222222" past
+# Attempt to create files with the latest and earliest possible dates for ext4. Nanoseconds are
+# special there, but not usually on other filesystems. In some touch implementations, the format
+# may be rejected. So if a command fails, we try again with a more extreme date that is out of
+# range, because some implementations will clip it to the edge of the range (but they may fail).
+touch -d '2446-05-10 22:38:55.111111111' future || touch -d '2446-05-11 22:38:56' future
+touch -d '1901-12-13 20:45:52.222222222' past || touch -d '1901-12-13 20:45:52' past