cp: Add tests involving sparse files.

[des]

Summary

Sponsored by: Klara, Inc.

[des]

As noted in D38191, our cp(1) transparently and unconditionally preserves holes when copying sparse files.

[des]

Remove test cases that make no sense without the -S option.

[des]

Pick nit in sparse_only_hole case.

[rmacklem]

I'm afraid I know nothing about the testing framework,
so I can't help with this one.

Good to see it being done though.

[markj]

Seems ok, though these tests might fail if run on unusual filesystems like msdosfs. I think we can address that later if it ever comes up though.

bin/cp/tests/cp_test.sh

314

Since these seem to be alphabetically sorted, the sparse tests should come before standalone_Pflag.

[des]

Order tests lexicographically.