As of bug 685559, comment 5, we now have a migration infrastructure on master, which allows to modify any config file in any way (very flexible, because it relies on regular expressions and not specific format).

commit 78b2778357fadd9dcfff5962cc79204b5c8bf0ef
Author: Jehan <jehan@girinstud.io>
Date:   Wed Dec 12 15:30:31 2012 +0900

    config: migration infrastructure to update configuration files.

    This is a generic system based off regular expressions so it can be used
    for any configuration file.
    Some of the use cases would be for instance to clean out outdated custom
    actions (hence remove some loading burden), or rename them (so that
    users don't lose their customization if we rename actions), etc.

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One of the conclusion is that we can update action names or groups for instance, without any risk of having angry users who would lose their customization, because we can now migrate their custom accelerator to the new action name.

We can also clean out old actions that we deleted, hence preventing them from cluttering config files with dozen of useless actions, and possibly having these lines out of the loading way.

And we can do other stuff that anyone may think of, involving updating any of the other configuration files.

I opened this ticket to discuss this. I am myself noted a few inconsistencies:

1/ view-close closes an image view. But file-close-all closes all image views. Shouldn't it be renamed to view-close-all for consistency?

2/ And why does the quit action is file-quit?! This has nothing file-related.

3/ Also all the dock-* actions are loaded but they are not available from UI and
customizable only by editing directly the menurc by hand. If we actually
consider they are not relevant anymore, why not delete them?

...