This can be used to keep both in sync in the period between
initial migration and eventual obsolence.
Note only non-obsoleted, migrated preferences are tracked.
We don't want to resync preferences that have been
obsoleted (reset). That would nullify the whole idea
of making them obsolete for future removal.
This commit only adds the mapping, synching will follow in a future
commit.
'deprecate' is technically a noop. It serves to remind maintainers
the 'deprecated' preference is to be obsoleted in the next major
release.
'obsolete' goes one step further in that it will cause gnucash to reset
the preference, effectively clearing the value stored in the preferences
backend. This is the final phase of a preference. Following this it
will be completely removed from the GSettings schema in the next
major release.
Notes
* 'deprecate' and 'migrate' are related. Both are a reminder the
preference is to be obsoleted in the next major release. 'deprecate'
does only that though while 'migrate' will also trigger a copy of
the old value to a new location in the databse.
* This commit readds a couple of preferences that had been removed
in the past to be able to properly obsolete them (and to test
the obsoleting code)
This commit mostly changes descriptions and variable names to
use the more generic terms 'transformations' or 'conversions'.
'migration' is only one possible transform, future commits will
add others.
There are no functional changes in this commit other than
a logic inversion in parse_one_release_node. It now checks
for nodes named 'migrate' rather than for nodes not named
'migrate' (the code is adapted accordingly to match this
logic change).
This makes sure all schema changes are in effect before
the first consumer can query them. For example this will
prevent a one-time re-occurrence of the tip of the day dialog
the first time the new migrations are run.
The rules for migration are read from an xml file. This file was
prepared in a previous commit. Future settings 'data model' changes can
reuse this code by simply adding migration rules in the xml file.
This replaces the hardcoded rules that were currently in place to
migrate a few settings from 2.6 and older to 3.0. These rules are no
longer meaningful as we require users to migrate from one major release
series to the immediate next one. So by the time the new migration rules
in this commit are applied by users they should already have run gnucash
3.x at least once. That run should have taken care of the pre-3.0
migration actions.
This was ported from GConf, but GSettings doesn't work that way.
Settings locations are defined at compile time and can't be
relocated at run time (unless you make all of the settings
explicitly relocatable. That however is not how GSettings is meant to be
used.)
