doc: glossary: add a reference for "epoch"

It comes up often enough and we need to ensure it's not
confused with IMAP "slices".

diff --git a/Documentation/public-inbox-glossary.pod b/Documentation/public-inbox-glossary.pod
index f17f2d28709a0641b39c7a14d25b5e546dcc02a6..710098c8c11510803b62f08a1cfcdf3784bd342c 100644 (file)
--- a/Documentation/public-inbox-glossary.pod
+++ b/Documentation/public-inbox-glossary.pod
@@ -67,6 +67,11 @@ rather than the newsgroup name since public-facing JMAP will be
 part of the PSGI code and not need a separate daemon like
 L<public-inbox-nntpd(1)> or L<public-inbox-imapd(1)>
 
+=item epoch
+
+A git repository used for blob storage.  See
+L<public-inbox-v2-format(5)/GIT EPOCHS>.
+
 =item keywords, (IMAP|Maildir) flags, mbox Status + X-Status
 
 Private, per-message keywords or flags as described in RFC 8621