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<div class="moz-cite-prefix">On 02/07/2019 04:16, Geoff Lankow
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:7ed1e7f5-2f2a-9b01-87d0-0fdfa14e015b@thunderbird.net">
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<p>I digress. My point is: why do we have this thing at all? Is
there a good reason we want to go to these lengths, other than
Downgrading Is A Bad Idea™? It can be removed with <a
moz-do-not-send="true"
href="https://searchfox.org/comm-central/rev/679db3c87c1a356a66433d6c2adf6fca1f20789f/mail/moz.configure#75">a
one line config change</a>.</p>
</blockquote>
<p>For Firefox, the main point was to stop users "shooting
themselves in the foot". Various items, especially the databases,
can't easily be downgraded. For example, I'm pretty sure if you
downgrade from the latest Firefox to ESR 60, and you'll find all
your history gone, and potentially other things like passwords or
form history. Bookmarks generally get recovered as there's a
separate backup mechanism for that for other reasons.</p>
<p>This doesn't necessarily just happen from the latest to an older
release, but also from one version to the next.</p>
<p>Whilst I can understand that sometimes users might want to try a
downgrade to a previous version, before now, they just ran the
risk of loosing data. Now Firefox stops this happening.</p>
<p>From a developer perspective it is also nicer - what was once
basically "downgrades are nice but not really supported" is now a
definite "downgrades are not supported", which allows us to be
more flexible about what changes we do and when they occur. As an
example, previously we might have batched up downgrade affecting
items so that a set happened on one release - now we can spread
them out for whenever they are ready and it doesn't matter so
much.</p>
<p>For Thunderbird it is potentially worth keeping it, for some of
the core items such as passwords, but also in case there's changes
to the mail storage format, or other things (preferences?) that
might cause dataloss on a downgrade.</p>
<p>Mark<br>
</p>
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