+It does not affect threading unless C<--rethread> is
+used.
+
+=item --all
+
+Index all inboxes configured in ~/.public-inbox/config.
+This is an alternative to specifying individual inboxes directories
+on the command-line.
+
+=item --rethread
+
+Regenerate internal THREADID and message thread associations
+when reindexing.
+
+This fixes some bugs in older versions of public-inbox. While
+it is possible to use this without C<--reindex>, it makes little
+sense to do so.
+
+Available in public-inbox 1.6.0+.
+
+=item --prune
+
+Run L<git-gc(1)> to prune and expire reflogs if discontiguous history
+is detected. This is intended to be used in mirrors after running
+L<public-inbox-edit(1)> or L<public-inbox-purge(1)> to ensure data
+is expunged from mirrors.
+
+Available since public-inbox 1.2.0.
+
+=item --max-size SIZE
+
+Sets or overrides L</publicinbox.indexMaxSize> on a
+per-invocation basis. See L</publicinbox.indexMaxSize>
+below.
+
+Available since public-inbox 1.5.0.
+
+=item --batch-size SIZE
+
+Sets or overrides L</publicinbox.indexBatchSize> on a
+per-invocation basis. See L</publicinbox.indexBatchSize>
+below.
+
+When using rotational storage but abundant RAM, using a large
+value (e.g. C<500m>) with C<--sequential-shard> can
+significantly speed up and reduce fragmentation during the
+initial index and full C<--reindex> invocations (but not
+incremental updates).
+
+Available in public-inbox 1.6.0+.
+
+=item --no-fsync
+
+Disables L<fsync(2)> and L<fdatasync(2)> operations on SQLite
+and Xapian. This is only effective with Xapian 1.4+. This is
+primarily intended for systems with low RAM and the small
+(default) C<--batch-size=1m>. Users of large C<--batch-size>
+may even find disabling L<fdatasync(2)> causes too much dirty
+data to accumulate, resulting on latency spikes from writeback.
+
+Available in public-inbox 1.6.0+.
+
+=item --sequential-shard
+
+Sets or overrides L</publicinbox.indexSequentialShard> on a
+per-invocation basis. See L</publicinbox.indexSequentialShard>
+below.
+
+Available in public-inbox 1.6.0+.
+
+=item --skip-docdata
+
+Stop storing document data in Xapian on an existing inbox.
+
+See L<public-inbox-init(1)/--skip-docdata> for description and caveats.
+
+Available in public-inbox 1.6.0+.
+
+=item -E EXTINDEX
+
+=item --update-extindex=EXTINDEX
+
+Update the given external index (L<public-inbox-extindex-format(5)>.
+Either the configured section name (e.g. C<all>) or a directory name
+may be specified.
+
+Defaults to C<all> if C<[extindex "all"]> is configured,
+otherwise no external indices are updated.
+
+May be specified multiple times in rare cases where multiple
+external indices are configured.
+
+=item --no-update-extindex
+
+Do not update the C<all> external index by default. This negates
+all uses of C<-E> / C<--update-extindex=> on the command-line.
+
+=item --since=DATESTRING
+
+=item --after=DATESTRING
+
+=item --until=DATESTRING
+
+=item --before=DATESTRING
+
+Passed directly to L<git-log(1)> to limit changes for C<--reindex>