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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Hi all,</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">The self-upgrade feature was introduced on March 20 [1], and there has been very little feedback so far, yet I have been told it raises some concerns so let me summarise the (simple) idea behind it and how it's expected to work. Note that it opens the gate for self-upgrades but the feature in itself doesn't trigger any new behaviour. I've more recently been adding version-checks [2] and a companion opam self-upgrade package [3].</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">* At startup, as soon as possible, OPAM checks if there is an 'opam' exe and 'opam.version' file in OPAMROOT.</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">* If the version is newer than current, OPAM exec()s it.</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">* We pass information through the environment to make sure that only happens once.</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">* You can bypass it with OPAMNOSELFUPGRADE=1 or --no-self-upgrade</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">* Information about what happens is present in several places to avoid surprises:</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"> - at the beginning of the debug log</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"> - in `opam config report`</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;"> - as a warning if the system version is not a release</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">* This is opt-in: the idea is to provide the opam and opam.version files through an opam package, that the user explicitely installs [3]. The package should explain what happens to the user (eg. via descr and post-messages).</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">* It can already be tested with `opam pin opam-bin git://github.com/ocaml/opam`. You need a recent version.</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">* It follows that upgrades may come through the opam-repository, or git if pinned.</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">I've attempted to make this as fool-proof as possible, and put good grounds first to enable further fixes within the opam package. The worst scenario I can think of is that your opam-self package is removed (failed to build, upgrade interrupted, or whatever reason). We then fallback to the system OPAM, that should still work ; if the repo format changed in the meantime, opam will advertise that it needs a newer version at startup, and you'll need to go through another channel to get it back. Annoying but not a critical failure, and we could mitigate this eg. with a backup advertised in the post_messages.</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">This feature has long been asked for [4] and I do think it is a useful one, if done right: it makes deployment of new versions faster and easier, helps people try out bleeding-edge versions if they want to, and generally makes upgrading easier for the user. Besides, people are expecting it.</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Cheers,</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">Louis</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">PS: I'm currently going through the bug-tracker and preparing a 1.2.0-beta</p>
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<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">[1] https://github.com/ocaml/opam/pull/1257</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">[2] https://github.com/ocaml/opam/pull/1440</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">[3] https://github.com/ocaml/opam/pull/1467</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px; -qt-user-state:0;">[4] https://github.com/ocaml/opam/issues/528</p>
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