There's a steady trickle of patches that need to be ported to the beta and stable branch. Only a few people are even aware of the process, but this is actually something anybody can do.
When somebody identifies a PR that should be backported to beta they tag it
That means they want one of the teams to evaluate whether the patch should be
backported. It is also suggested applying the
I-nominated and and a
T- (team) tag
as appropriate: that'll really get their attention. Anybody with triage access
is free to make these tags. Backports are mostly done to fix regressions. If the
team thinks it should be backported they'll then additionally tag it
At that point the PR is ready to be backported. So the list of patches ready for
a backport is those tagged
So now somebody needs to go through those PR's and cherry-pick their commits to
the beta branch. Those cherry-picks are then submitted as a PR against the
beta branch, with a title started with
[beta] (so reviewers can see its
specialness). The OP of that PR should contain links to all the PRs being
backported. Here's an example.
Anybody can make these PRs!
After that a reviewer needs to verify that the backport looks correct, that it's
submitted to the beta branch, and then approve via
@bors: r+. Finally, they
need to follow the links to the original PRs and remove the
tag (people forget to do this a lot). This last step indicates that the
backport has been completed, so the
have three states.
If, on the other hand, a backport is declined the
beta-nominated label is
removed, closing the procedure.
Backports to the stable branch work exactly the same as beta ones, labels have
just a slightly different name:
stable-nominated identifies a PR to be
discussed for a backport and
stable-accepted is a PR accepted for
backport. Declined stable nomination will have the
T-release will decide on a case by case basis if a stable backport will
warrant a point (.patch) release (f.e. release a
The procedure for backporting fixes to Cargo is similar but slightly more
extended than the
rust-lang/rust repo's procedure. Currently there aren't
backport tags in the Cargo repository, but you'll initiate the backport process
by commenting on an associated PR, requesting a backport. Once a Cargo team
member has approved the backport to happen you're good to start sending PRs!
First you'll send a PR to the
rust-1.21.0branch of Cargo (replace 1.21 with the current rustc beta version number). Like with
rust-lang/rustyou'll prefix the title of your PR with
[beta]and ensure it's flagged as going to beta.
Next a Cargo reviewer will
@bors: r+the PR and put it into the queue. Eventually bors will automatically merge the PR (when tests are passing) to the appropriate Cargo branch.
Finally you'll send a PR to the
betabranch, updating the Cargo submodule. The Cargo submodule should be updated to the tip of the
rust-1.21.0branch (the branch your Cargo PR was merged to). As like before, ensure you've got
[beta]in the PR title.
After that's all said and done the Cargo change is ready to get scheduled onto the beta release!