Add branch date to index page

This helps teams plan for when we're close to cut off points, rather than
planning around the stable date (which is important only for backports, really).

Author: Mark-Simulacrum

js/index.js

@@ -7,12 +7,14 @@ const DATE_FORMAT = 'MMMM DD YYYY'
 const newReleases = Math.floor(moment.utc().diff(EPOCH_DATE, 'weeks') / 6)
 
 function addRelease (kind, incr, toolsWeek) {
-  const releaseNumber = EPOCH_RELEASE + newReleases + incr
-  const displayVersion = `1.${releaseNumber}`
-  const releaseDate = EPOCH_DATE.clone().add((newReleases + incr) * 6, 'weeks')
+  const releaseNumber = EPOCH_RELEASE + newReleases + incr;
+  const displayVersion = `1.${releaseNumber}`;
+  const releaseDate = EPOCH_DATE.clone().add((newReleases + incr) * 6, 'weeks');
+  const branchDate = EPOCH_DATE.clone().add((newReleases + incr) * 6, 'weeks').subtract(6, 'days');
 
   document.querySelector(`#${kind}-version`).textContent = displayVersion
   document.querySelector(`#${kind}-release-date`).textContent = `${releaseDate.format(DATE_FORMAT)} UTC`
+  document.querySelector(`#${kind}-branch-date`).textContent = `${branchDate.format(DATE_FORMAT)} UTC`
 
   if (toolsWeek) {
     const noBreakagesTo = releaseDate.clone().subtract(6, 'weeks').day(2)

src/README.md

@@ -9,7 +9,7 @@ file an issue or PR on the [Rust Forge GitHub].
 
 ### Help Wanted
 
-Want to contribute to Rust, but don't know where to start? Here's a list of 
+Want to contribute to Rust, but don't know where to start? Here's a list of
 `rust-lang` projects that have marked issues that need help and issues that are
 good first issues.
 
@@ -35,12 +35,15 @@ Avoid changing the "Current Release Versions" without also updating the selector
 in `js/index.js`.
 -->
 
-Channel    | Version | Will be stable on
------------|---------|------------------
-Stable     | <span id="stable-version"></span>  | <span id="stable-release-date"></span>
-Beta       | <span id="beta-version"></span>    | <span id="beta-release-date"></span>
-Nightly    | <span id="nightly-version"></span> | <span id="nightly-release-date"></span>
-Nightly +1 | <span id="next-version"></span>    | <span id="next-release-date"></span>
+Channel    | Version | Will be stable on | Will branch from master on |
+-----------|---------|-------------------|----------------------------|
+Stable     | <span id="stable-version"></span>  | <span id="stable-release-date"></span>  | <span id="stable-branch-date"></span>
+Beta       | <span id="beta-version"></span>    | <span id="beta-release-date"></span>    | <span id="beta-branch-date"></span>
+Nightly    | <span id="nightly-version"></span> | <span id="nightly-release-date"></span> | <span id="nightly-branch-date"></span>
+Nightly +1 | <span id="next-version"></span>    | <span id="next-release-date"></span>    | <span id="next-branch-date"></span>
+
+See the [release process](./release/process.md) documentation for details on
+what happens in the days leading up to a release.
 
 ### No Tools Breakage Week
 To ensure the beta release includes all the tools, no [tool breakages] are