[PATCH] doc: extindex: note the use of `newsgroup' entries

[PATCH] doc: extindex: note the use of `newsgroup' entries

[Eric Wong]

We'll also be using this for -cindex for associating inboxes
to coderepos.
---
 coderepo <=> inbox association is proving tricky and slow :<
 and xapian-delve + quest CLI tools aren't enough...

 Documentation/public-inbox-extindex.pod | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/public-inbox-extindex.pod b/Documentation/public-inbox-extindex.pod
index 66e04060..a5f699c5 100644
--- a/Documentation/public-inbox-extindex.pod
+++ b/Documentation/public-inbox-extindex.pod
@@ -93,6 +93,12 @@ Putting an C<extindex> entry in the config allows L<PublicInbox::WWW>.
 You can have any number of C<extentry.$NAME> sections where C<$NAME>
 is something other than C<all> to display a union of several inboxes.
 
+It is strongly recommended any public inboxes indexed by this command
+have a stable C<publicinbox.$NAME.newsgroup> entry (regardless of
+the presence of an NNTP or IMAP server).  Otherwise, public-inbox-extindex
+will use C<publicinbox.$NAME.inboxdir> as an internal key which can
+cause needless reindexing and require L<--gc> if inboxes are relocated.
+
 See L<public-inbox-config(5)> for more details.
 
 =head1 ENVIRONMENT