postgresql-setup: fix upgrade bug with non-default unit names

We can't always use '$upgradefrom_id' as "default" previous
service name.  This broken in-place upgrades with
'--unit postgresqlPORT' (old style service files layout) or
'postgresql@port'.  Now, by default, use the same service name
for both older and newer PG stack.

While we are on it, make it a bit more automatic and pick
'postgresql92@second' as "older stack" if upgrading into unit
'postgresql93@second'.

Add new option --upgrade-from-unit which allows us to override
default decision.

* postgresql-setup.in: Set 'option_upgradefrom_unit' to hopefully
correct default.  Add new info message in case we are not
upgrading from differently named unit.
(USAGE_STRING): Document new --upgrade-from-unit option.
(service_configuration): Don't fork based on $mode and simply use
fourth parameter as 'service'.  Fix the debug message a bit.
(long_opts): Add new option upgrade-from-unit.
* NEWS: Document.

1 files changed, 9 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index d402ac2..989a308 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,14 @@
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+Bugfixes in 3.4 version
+
+* Fix upgrade for non-standard unit names with --unit option.
+
+* Add --upgrade-from-unit option which allows proper selection of
+  predecessor service name (when the default detection does not help).
+
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
 Bugfixes in 3.3 version
 
 * The PGPORT/PGOPTS/.. variables should be correctly forwarded down from