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Split recipes at . surrounded by whitespace instead of any .

Johannes Truschnigg requested to merge colo/partman-auto-raid:enable-dots-in-extra-args into master

Without this patch, it is impossible to pass in EXTRA_ARGS to mdadm during array creation that choose any md-specific superblock/metadata format other than 0.90 or 1.2, because any "." character (ASCII 0x2e) will be used to split the list of recipes.

As of mdadm 4.2 (Debian bookworm), the -e/--metadata option is implemented and documented as follows:

-e, --metadata= Declare the style of RAID metadata (superblock) to be used. The default is 1.2 for --create, and to guess for other op‐ erations. The default can be overridden by setting the metadata value for the CREATE keyword in mdadm.conf.

 Options are:

 0, 0.90
        Use the original 0.90 format superblock.  This  for‐
        [...]

 1, 1.0, 1.1, 1.2 default
        Use  the  new version-1 format superblock.  This has
        fewer restrictions.  It can easily be moved  between
        hosts with different endian-ness, and a recovery op‐
        eration can be checkpointed and restarted.  The dif‐
        ferent  sub-versions store the superblock at differ‐
        ent locations on the device, either at the end  (for
        1.0),  at  the  start (for 1.1) or 4K from the start
        (for 1.2).  "1" is equivalent to "1.2" (the commonly
        preferred 1.x format).  "default" is  equivalent  to
        "1.2".

Hence, the following pre-seed stanza should be fit to create a RAID1 array with a version 1.0 md superblock on /dev/sd[ab]1:

d-i partman-auto-raid/recipe string
1 2 0 fat32 - /dev/sda1#/dev/sdb1 # --metadata=1.0 .
1 2 0 lvm - /dev/sda2#/dev/sdb2 .

Without this patch, partman-auto-raid fails to properly split the provided recipe into its intended two parts, and will end up with three broken individual recipes (with one gratuitous split in the middle of "1.0") instead.

Superblock versions other than 0.90 and 1.2 can be useful under various circumstances, such as when trying to provide ESP (EFI System Partition) redundancy without any specific userland tricks to copy data from one "primary" ESP to any others.

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