Cleanup the handling of --strategy-option now that we no longer need to
support "--preserve-merges" and properly quote the argument when saving
it to disc.

A hopefully final re-roll to fix a memory leak I spotted in V3.

Changes since V3:
 - Fixed a memory leak added in V3. The array returned by
   split_cmdline() is allocated on the heap so we need to fee it. The
   array elements come from the string passed to split_cmdline() so do
   not need to be individually freed.

Changes since V2:

 - Added Elijah's Reviewed-by: trailer.
 - Fixed a typo in patch 4 spotted by Elijah.

Changes since V1:

I've rebased these patches onto 'master' to avoid conflicts with
'sg/parse-options-h-initializers' in the new patch 2 (this series
depends on 'ab/fix-strategy-opts-parsing' but that has now been merged
to master).

Patch 1 - Unchanged.

Patch 2 - New patch to store the merge strategy options in an "struct
          strvec". This patch also introduces a new macro OPT_STRVEC()
          to collect options into an "struct strvec".

Patch 3 - Small simplification due to the changes in patch 2.

Patch 4 - Moved the code to quote a list so it can split by
          split_cmdline() into a new function quote_cmdline() as
	  suggested by Elijah.

Patch 5 - Reworded the commit message as suggested by Elijah.


Version: 4
Message-ID: <cover.1681117706.git.phillip.wood@dunelm.org.uk>
Submitted-As: https://lore.kernel.org/git/cover.1681117706.git.phillip.wood%40dunelm.org.uk