Profile Reversion

[grumpfish]

Please provide a feature to revert back to a previous profile after it has been "upgraded" by allowing a new version to Firefox to be installed.

In a corporate area where machine images are restored overnight the version of Firefox is reverted.  Even having turned off all the automatic update features, an accidental click on the update button renders Firefox unusable from the next day because it won't start with a newer profile than the version running without creating a new one and losing all shortcuts & stored passwords, until such time as the corporate IT team update the image version.

[Jon]

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[SamB]

Psychic debugging tells me that IT may want to use the DisableAppUpdate policy instead of the AppAutoUpdate policy.

This could be a good feature, though; the tricky part is that profiles can be arbitrarily large, and you really don't want to do something that could suddenly fill the disk up without user oversight.

It does not seem that it would be particularly tricky to actually backup the profile before upgrading it; the code that checks version compatibility to avoid corrupting newer profiles starts at https://searchfox.org/mozilla-central/rev/02841791400cf7cf5760c0cfaf31f5d772624253/toolkit/xre/nsApp...: this seems to be exactly when where you'd want to do such a backup, since it already has the versions and knows how to compare them, and in order to actually prevent profile corruption, it already runs before anything else that would write to the profile.