[co19] Document how co19 rolls are done.

Change-Id: Ie0fecc0ca5c17f0a875988fe90c1b12f6052a975
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/107290
Reviewed-by: Alexander Thomas <athom@google.com>

DEPS

@@ -36,6 +36,8 @@ vars = {
   "chromium_git": "https://chromium.googlesource.com",
   "fuchsia_git": "https://fuchsia.googlesource.com",
 
+  # co19 is a cipd package. Use tests/co19_2/update.sh to update this hash.
+  # It requires access to the dart-build-access group, which EngProd has.
   "co19_2_rev": "d2c051f7537e6fe47c8ccf0bd7a7e84b02010a2a",
 
   # As Flutter does, we use Fuchsia's GN and Clang toolchain. These revision

tests/co19_2/update.sh

@@ -0,0 +1,71 @@
+#!/usr/bin/env bash
+# Uploads a new version of the co19 CIPD packages.
+# This script requires access to the dart-build-access group, which EngProd has.
+
+set -e
+set -x
+
+if [ ! -e tests/co19_2 ]; then
+  echo "$0: error: Run this script at the root of the Dart SDK" >&2
+  exit 1
+fi
+
+# Find the latest co19 commit.
+rm -rf tests/co19_2/src.git
+git clone https://dart.googlesource.com/co19 tests/co19_2/src.git
+CO19=tests/co19_2/src.git
+OLD=$(gclient getdep --var=co19_2_rev)
+NEW=$(cd $CO19 && git fetch origin && git rev-parse origin/master)
+
+git fetch origin
+git branch cl-co19-roll-co19-to-$NEW origin/master
+git checkout cl-co19-roll-co19-to-$NEW
+
+# Build a cipd package of the commit.
+BUILD_ID=$(bb add \
+              -commit https://dart.googlesource.com/co19/+/$NEW \
+              -json \
+              dart/ci/co19-roller \
+             | jq '.id' \
+             | tr -d '"')
+bb collect -interval 10s $BUILD_ID
+
+# Update DEPS:
+gclient setdep --var=co19_2_rev=$NEW
+
+# Make a nice commit. Don't include the '#' character to avoid referencing Dart
+# SDK issues.
+git commit DEPS -m \
+  "$(printf "[co19] Roll co19 to $NEW\n\n" &&
+     cd $CO19 &&
+     git log --date='format:%Y-%m-%d' --pretty='format:%ad %ae %s' \
+       $OLD..$NEW | tr -d '#')"
+
+rm -rf tests/co19_2/src.git
+
+GIT_EDITOR=true git cl upload
+ISSUE=$(git config --get branch.cl-co19-roll-co19-to-$NEW.gerritissue)
+
+BUILDERS=$(jq '.builder_configurations|
+                map(select(.steps|
+                           any(.arguments|
+                               select(.!=null)|
+                               any(.=="co19_2"))))|
+                map(.builders)|
+                flatten|
+                sort' \
+                tools/bots/test_matrix.json \
+             | tr -d '[",]')
+
+git cl try -B luci.dart.try $(for BUILDER in $BUILDERS; do echo -b $BUILDER-try; done)
+
+git cl web
+
+set +x
+cat << EOF
+
+Wait for the builders to finish. If any failed, pre-approve them:
+
+  tools/sdks/dart-sdk/bin/dart tools/approve_results.dart \
+    -p https://dart-review.googlesource.com/c/sdk/+/$ISSUE
+EOF