Review catch (argus): most of the pre-existing script body picked up ~14
leading spaces it never had, because replacing an inline `optionalString`
with a named binding changed what the formatter treated as the block's
base indent. Functionally invisible — nix strips the minimum common
indentation and bash ignores the rest — but it made the diff read as
"reindented everything, incidentally added a block" instead of "added a
block".
Net diff on this file is now 231 insertions and 2 deletions.
3de7a4a1b1