+(e.g. "glass" or "honey"), but is designed to tolerate and
+accept parallel Xapian database modifications from
+L<public-inbox-watch(1)>, L<public-inbox-mda(1)>,
+L<public-inbox-learn(1)>, and L<public-inbox-index(1)>.
+
+This command is rarely used, as Xapian DB formats rarely
+change.
+
+=head1 OPTIONS
+
+=over
+
+=item --all
+
+Copy all inboxes configured in ~/.public-inbox/config.
+This is an alternative to specifying individual inboxes directories
+on the command-line.
+
+=item -c
+
+=item --compact
+
+In addition to performing the copy operation, run L<xapian-compact(1)>
+on each Xapian shard after copying but before finalizing it.
+Compared to the cost of copying a Xapian database, compacting a
+Xapian database takes only around 5% of the time required to copy.
+
+Compared to L<public-inbox-compact(1)>, use of this option is
+preferable for gigantic inboxes where the coarse-grained lock
+currently required for L<public-inbox-compact(1)> can cause
+the compaction to take hours at-a-time.
+
+=item -R N
+
+=item --reshard=N
+
+Reshard the Xapian database on a L<v2|public-inbox-v2-format(5)>
+inbox to C<N> shards . Since L<xapian-compact(1)> is not suitable
+for merging, users can rely on this switch to reshard the
+existing Xapian database(s) to any positive value of C<N>.
+
+This is useful in case the Xapian DB was created with too few or
+too many shards given the capabilities of the current hardware.
+
+=item --blocksize
+
+=item --no-full
+
+=item --fuller
+
+These options are passed directly to L<xapian-compact(1)> when
+used with C<--compact>.