Add a utility method that can be used to align data to the next "grain"
which is currently defined as 1 MiB -- the default used by sfdisk.
Add corresponding tests.
The method assert.GreaterOrEqual(t, a, b) asserts that a >= b,
but the arguments were (expected, actual), which is the wrong
way around since we want to assure that the actual size is at
least the expected size, i.e. actual >= expected and thus the
argument should be (actual, expected).
The partition table size (pt.Size) is in sectors while our checks and
customizations are in bytes, so we need to convert when comparing.
Co-Authored-By: Achilleas Koutsou <achilleas@koutsou.net>
Modify the signature of `CreatePartitionTable` so that it is
possible to return errors from the function. This is not yet
used, but will be in the near future. Change all call sites
accordingly: in most cases we can just bubble up the error.
Pass the `basePartitionTable` argument of `CreatePartitionTable`.
Now that we clone the partition table at the beginning of the
method there is no need to pass a copy of the partition table.
