1237778 - Create obsolescence markers for changesets landed by Lando

Status: RESOLVED WONTFIX

(Conduit Graveyard :: Transplant, defect, P3)

Description

[Gregory Szorc [:gps]]

I love hitting the autoland button from MozReview. What I don't like is the original changesets persisting in my local Mercurial repos. I wish they'd "disappear" automagically whenever I pulled down the autolanded/rebased changesets.

We could get this magical disappearing behavior if we produced obsolscence markers for autolanded changesets.

I'd like to see Autoland produce obsolscence markers for rebased changesets. This will require enabling obsolescence on hg.mozilla.org (currently it can be enabled for user repos only).

Obsolsecence markers still don't scale to infinity. So, we can't have everyone pushing obsolsecence markers to every repo on hg.mozilla.org, especially mozilla-central. We also probably don't want to mark changesets in the repo as obsolete, as this can result in wonkiness which I don't want to inflict on Mozillians just yet.

What we can do is enable the pushing of obsolescence markers when the push user is autoland. And, we can have a push hook verify that new obsolscence markers don't obsolete changesets in the repo. In other words, we'll only create markers whose source was an unpublished changeset from MozReview (or wherever).

Before we commit to this, I'll probably want to talk to some Mercurial devs about the implications of this, since obsolescence is still somewhat in flux and there could be fallout from the proposed implementation above.

Comment 1

[Dan Minor [:dminor]]

I agree having the original changesets around is annoying.

One problem I've had in the past in Autoland, is that if I pull from the MozReview repo, rebase the changesets, and subsequently hit an error pushing to the destination repository and retry from MozReview, hg doesn't want to let me pull the changesets from MozReview from again because they're still in Autoland's repository, just hidden because of the rebase. I didn't find a good way of cleaning this up (admittedly, I think I just tried stripping the offending changesets and then gave up) so I ended up disabling obsolescence on Autoland.

Comment 2

[Gregory Szorc [:gps]]

We may have to do something like delete the obsolsecence markers from the autoland repo after every rebase. If you delete the obsolsecence markers, the changesets should become unhidden.