learn repository retrycount configuration option

Allow retrying the download of messages more than twice.

Signed-off-by: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap.conf

@@ -1270,6 +1270,26 @@ remoteuser = username
 #"cvlc --play-and-stop --play-and-exit /path/to/sound/file.mp3 > /dev/null 2>&1")
 
 
+# This option stands in the [Repository RemoteExample] section. [TESTING]
+#
+# Operating under extreme network conditions (China) network connectivity
+# especially for SSL can be so bad and so slow that absolutely every possible
+# kind of connectivity error that can occur does occur.
+#
+# Rather than have offlineimap exit on errors it may be preferable to have it
+# simply retry fetching of messages dozens of times.  The alternative is to
+# restart offlineimap in a constant loop, which may involve using significant
+# CPU cycles (if the repository is large) to load up the UID database again.
+#
+# This option is best utilised in combination with socktimeout, which catches
+# instances of interference by e.g. the GFW at the TCP layer, as well as China
+# ISPs simply not coping.
+#
+# Default value: retrycount = 2
+#
+#retrycount = 2
+
+
 # This option stands in the [Repository RemoteExample] section.
 #
 # If offlineiamp is having troubles to download some UIDS, it's possible to get