Create dev18.0.x branch checklist

[drewnoakes]

• Identify base commit for new branch
  • According to the schedule, main snapped to rel/d18.0 on 22 August 2025 at 12PM PDT
  • Last completed Project System insertion PR: https://dev.azure.com/devdiv/DevDiv/_git/VS/pullrequest/664018
  • Last inserted GitHub PR: Fixes default value for runningUnderDebugger #9742
  • Merge commit of that PR: 0fc481a
• Create branch on GitHub at that commit
  • https://github.com/dotnet/project-system/tree/dev18.0.x
• For branches not matching dev* or feature/* (usually we skip these)
  • Update the pull-request.yml (via pr) to support PR builds
  • Update the official.yml (via trigger) to have signed builds the new branch
• Update version.json (via "version") to match the version of VS, if needed
  • In new branch: https://github.com/dotnet/project-system/blob/dev18.0.x/version.json ([dev18.0.x] Update version from 17.14 to 18.0 #9752)
  • In main: https://github.com/dotnet/project-system/blob/main/version.json (Update version from 17.14 to 18.0 #9751)
• In the new branch, update the "Build VS Bootstrapper" task in build-official-release.yml and set channelName to match the VS insertion branch.
  • E.g., for VS main the channelName is "int.main"; for rel/d17.8 it would be "int.d17.8"; etc.
• To run manual insertions, use the DotNet-Project-System pipeline. Enter the GitHub branch as Branch/tag, the VS branch as VS Insertion Branch Name, and check Create VS Insertion PR.
• Update Policy Service milestone tracking

[drewnoakes]

On hold. This checklist works well for upgrades within the 17.x family, but isn't sufficient for 17->18.