db.c: implemented incremental migration

In the past, normal migration was possible only if the actual
schema version differed from the version used in DB by 1. For
example, if DB uses an old version 3 and you need to use it
with the code written for version 5, the check_db_revision()
will convert it to 4 and DB will still use incompatible schema
version during Osmo-NITB running time. After next run it will
be converted to version 5.

This patch replaces a set of 'else-if' checks by a 'switch'
without 'break' statements between 'case' labels (waterfall).
It makes you able to migrate from current version to the
latest despite any difference between them.

Change-Id: Ia9c2aa86f96b88ad8a710d0a23879ce219bc82dc
Reviewed-on: https://gerrit.osmocom.org/62
Tested-by: Jenkins Builder
Reviewed-by: Holger Freyther <holger@freyther.de>

0 files changed, 0 insertions, 0 deletions