Partition map rewriter

[boredzo]

There are two cases in which impluse may need to make changes to a partition map:

• The volume needs to change size (#29). In this case, the partition length for the corresponding partition needs to change, as do the start block numbers for any and all subsequent partitions.
• The original partition map is in the IM4 format (#23). Just as modern macOS can't read original HFS, it can't read IM4 partition maps either. So, just as impluse exists to convert HFS volumes to HFS+, it should also convert IM4 partition maps to IM5.

[boredzo]

One thing that may be important/necessary is including a driver in the rewritten partition map.

My default inclination is to transfer any and all drivers from the original partition map. When it's an IM5 partition map and we're just resizing a partition, that should be fine. When it's an IM4 partition map, that may get trickier—a driver included in an IM4 partition map might try to read the disk's partition map, and panic (or, worse, corrupt data) if the partition map is in a different format.

[boredzo]

One consequence of this is that the converter should not simply copy any bytes before and after the volume. Those should be left to the partition map copier/rewriter to copy anything not in a partition or in a non-HFS partition.

Also part of this work: Finally deciding what impluse does for multiple HFS partitions. My guess is going to be to convert all HFS partitions by default, maybe with an option like --only-partition[s] that specifies one or more partitions by either order in the partition map, partition name, or volume name.

Possible optional syntax: <partition type>:<partition/volume name>. Like, Apple_HFS:Macintosh HD. Dunno if there's a need for that.

Also, partition: and volume: prefixes before partition/volume names, with p: and v: accepted as synonyms. So the partition-spec syntax would be (?P<partition_type>[^:]+:)?(?P<key_prefix>(?:partition|p|volume|v):)?(?P<name>.+). Valid partition-specs would include Macintosh HD, v:Macintosh HD, Apple_HFS:Macintosh HD, and the fully-qualified Apple_HFS:v:Macintosh HD.