C<--jobs=0> is accepted as of public-inbox 1.6.0 (PENDING)
to disable parallel indexing.
-If the inbox has not been indexed, C<JOBS - 1> shards
-will be created (one job is always needed for indexing
+If the inbox has not been indexed or initialized, C<JOBS - 1>
+shards will be created (one job is always needed for indexing
the overview and article number mapping).
Default: the number of existing Xapian shards