improve steps for the beta promotion

Author: pietroalbini

src/release/process.md

@@ -49,38 +49,24 @@ RUSTUP_DIST_SERVER=https://dev-static.rust-lang.org rustup update stable
 
 ## Promote master to beta (T-2 days, Tuesday)
 
-We need to find out the parent commit in which the PR opened last Monday merged.
-
-Go to that PR, and find the "bors merged commit $SHA into rust-lang:master at the bottom.
-
-Locally, run `` export BRANCH_POINT=`git rev-parse $SHA^` `` in the rust-lang/rust
-checkout. This should be bors-authored merge into master of the PR before the
-version bump merged.
-
-Create a new branch on `rust-lang/cargo` for the new beta. Here, `rust-lang` is
-the remote for https://github.com/rust-lang/rust.git. Replace `YY` with the
-minor version of master. First determine the branch point for cargo in
-`rust-lang/rust`, and then create a new branch:
+Gather the relevant information and push the new Cargo branch:
 
 ```sh
-cd rust
-git fetch rust-lang
+git fetch git@github.com:rust-lang/rust
+BRANCH_POINT=`git log --merges --first-parent --format="%P" -1 master -- src/version | awk '{print($1)}'`
 NEW_BETA_VERSION=`git show $BRANCH_POINT:src/version`
 CARGO_SHA=`git rev-parse $BRANCH_POINT:src/tools/cargo`
+
 cd src/tools/cargo
 git branch rust-$NEW_BETA_VERSION $CARGO_SHA
-git push origin rust-$NEW_BETA_VERSION
+git push git@github.com:rust-lang/cargo rust-$NEW_BETA_VERSION
 ```
 
-You'll need to temporarily disable branch protection on GitHub to push the new
-branch.
-
 Temporarily disable banch protection on GitHub for the `beta` branch of the Rust
 repo. Promote rust-lang/rust's master branch to beta as with yesterday:
 
 ```sh
-$ git fetch rust-lang
-$ git push rust-lang $BRANCH_POINT:beta -f
+git push git@github.com:rust-lang/rust $BRANCH_POINT:beta -f
 ```
 
 Re-enable branch protection on GitHub. Send a PR to the freshly created beta