manual: improve sqlite section

Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

docs/offlineimap.txt

@@ -198,7 +198,7 @@ monthly folders, and ignore every folder that is more than 2-3 months old,
 this lets me only inspect a fraction of my Mails on every sync. If you haven't
 done this yet, do it :). See the folderfilter section in offlineimap.conf.
 
-3. The cache.
+3. The sqlite cache.
 +
 OfflineImap caches the state of the synchronisation to e.g. be able to determine
 if a mail has been added or deleted on either side.
@@ -206,14 +206,14 @@ if a mail has been added or deleted on either side.
 The historical status cache is a plain text file that writes out the complete
 file for each single new message (or even changed flag) to a temporary file. If
 you have plenty of files in a folder, this is a few hundred kilo to megabytes
-for each mail and is bound to make things slow. The default status cache uses
-sqlite. This saves plenty of disk activity. The sqlite engine and the Python
-sqlite module must installed. See the status_backend = plain setting in the
-offlineimap.conf.
+for each mail and is bound to make things slow. The latest default status cache
+is sqlite. This saves plenty of disk activity. The sqlite engine and the Python
+sqlite module must be installed. Enable the 'status_backend = plain' setting in
+'offlineimap.conf' for legacy compatibility with versions prior to '6.4.0'.
 +
 If you switch the backend from plain to sqlite, you may want to delete the old
-cache directory in <metadata>/Account-<account>/LocalStatus manually once
-you are sure that things work.
+cache directory in '<metadata>/Account-<account>/LocalStatus' manually (the
+sqlite cache stands in the 'LocalStatus-sqlite' folder).
 
 4. Use quick sync.
 +
@@ -233,37 +233,6 @@ you can set this to True. If you set it to False, you lose some of that
 safety, trading it for speed.
 
 
-Upgrading from plain text to SQLite cache format
-------------------------------------------------
-
-OfflineImap uses a cache to store the last known status of mails (flags etc).
-
-Historically that has meant plain text files, but recently we introduced
-sqlite-based cache, which helps with performance and CPU usage on large
-folders.  Here is how to upgrade existing plain text cache installations to
-sqlite based one:
-
-1. Sync to make sure things are reasonably similar.
-
-2. Change the account section to "status_backend = sqlite".
-
-3. Run a new sync.
-+
-This will convert your plain text cache to an sqlite cache (but leave
-the old plain text cache around for easy reverting). This must be quick and
-not involve any mail up/downloading.
-
-4. See if it works! :-)
-
-5. If it does not work, go back to the old version or set "status_backend = plain"
-
-6. Delete the old text cache files.
-
-Once you are sure it works, you can delete the
-~/.offlineimap/Account-foo/LocalStatus folder (the new cache will be in the
-LocalStatus-sqlite folder)
-
-
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