doc: add some notes around -xcpdb / -edit / -purge

These rarely-used commands have some caveats that needed
expanding on.

3 files changed, 41 insertions, 2 deletions

diff --git a/Documentation/public-inbox-edit.pod b/Documentation/public-inbox-edit.pod
index c64b4da8..3853fa9c 100644
--- a/Documentation/public-inbox-edit.pod
+++ b/Documentation/public-inbox-edit.pod
@@ -91,6 +91,20 @@ See L<public-inbox-config(5)>
 
 Only L<v2|public-inbox-v2-format(5)> repositories are supported.
 
+This is safe to run while normal inbox writing tools
+(L<public-inbox-mda(1)>, L<public-inbox-watch(1)>,
+L<public-inbox-learn(1)>) are active.
+
+Running this in parallel with L<public-inbox-xcpdb(1)> or
+C<"public-inbox-index --reindex"> can lead to errors or
+edited data remaining indexed.
+
+Incremental L<public-inbox-index(1)> (without C<--reindex>)
+is fine.
+
+Keep in mind this is a last resort, as it will be distruptive
+to anyone using L<git(1)> to mirror the inbox being edited.
+
 =head1 CONTACT
 
 Feedback welcome via plain-text mail to L<mailto:meta@public-inbox.org>
diff --git a/Documentation/public-inbox-purge.pod b/Documentation/public-inbox-purge.pod
index 56a3f95a..e20e18df 100644
--- a/Documentation/public-inbox-purge.pod
+++ b/Documentation/public-inbox-purge.pod
@@ -51,6 +51,20 @@ See L<public-inbox-config(5)>
 
 Only L<public-inbox-v2-format(5)> inboxes are supported.
 
+This is safe to run while normal inbox writing tools
+(L<public-inbox-mda(1)>, L<public-inbox-watch(1)>,
+L<public-inbox-learn(1)>) are active.
+
+Running this in parallel with L<public-inbox-xcpdb(1)> or
+C<"public-inbox-index --reindex"> can lead to errors or
+purged data remaining indexed.
+
+Incremental L<public-inbox-index(1)> (without C<--reindex>)
+is fine.
+
+Keep in mind this is a last resort, as it will be distruptive
+to anyone using L<git(1)> to mirror the inbox being purged.
+
 =head1 CONTACT
 
 Feedback welcome via plain-text mail to L<mailto:meta@public-inbox.org>
diff --git a/Documentation/public-inbox-xcpdb.pod b/Documentation/public-inbox-xcpdb.pod
index 89eed079..2ed4c582 100644
--- a/Documentation/public-inbox-xcpdb.pod
+++ b/Documentation/public-inbox-xcpdb.pod
@@ -11,8 +11,9 @@ public-inbox-xcpdb - upgrade Xapian DB formats
 public-inbox-xcpdb is similar to L<copydatabase(1)> for
 upgrading to the latest database format supported by Xapian
 (e.g. "glass" or "honey"), but is designed to tolerate and
-recover from Xapian database modifications from
-L<public-inbox-watch(1)> or L<public-inbox-mda(1)>.
+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)>.
 
 =head1 OPTIONS
 
@@ -80,6 +81,16 @@ used by public-inbox, NOT users upgrading public-inbox itself.
 In particular, it DOES NOT upgrade the schema used by the
 PSGI search interface (see L<public-inbox-index(1)>).
 
+=head1 LIMITATIONS
+
+Do not use L<public-inbox-purge(1)> or L<public-inbox-edit(1)>
+while this is running; old (purged or edited data) may show up.
+
+Normal invocations L<public-inbox-index(1)> can safely run
+while this is running, too.  However, reindexing via the
+L<public-inbox-index(1)/--reindex> switch will be a waste of
+computing resources.
+
 =head1 CONTACT
 
 Feedback welcome via plain-text mail to L<mailto:meta@public-inbox.org>