Register dotnetup with BAR for channel-based publishing

[dsplaisted]

Register dotnetup with BAR for channel-based publishing

Adds Build Asset Registry (BAR) registration to every non-PR dotnetup build, on top of the existing pipeline-artifact publishing. This is the prerequisite for shipping the dotnetup standalone executables to anonymous-access blob storage (ci.dot.net/public/dotnetup/<SemVer>/) with stable aka.ms/dotnet/dotnetup/daily/<file> shortlinks.

Tracks #54254.

What this PR does

Adds a new publish_to_bar stage to .vsts-dnup-ci.yml that runs on every non-PR build of release/dnup. The stage is additive — it does not change anything about the existing dotnetup-standalone-* pipeline artifacts, which continue to be published exactly as today. It only:

1. Downloads each per-RID dotnetup-standalone-* pipeline artifact (8 RIDs) onto a Windows agent.
2. Stages all 16 binary + .sha512 files flat under BlobArtifacts/. This flat layout is required because Arcade's PublishArtifactsInManifestBase.DownloadFileAsync fetches source blobs by basename only when the promotion pipeline runs.
3. Generates a v3 MergedManifest.xml whose <Blob Id="dotnetup/<SemVer>/<file>" /> entries serve a dual purpose: the basename is the source path inside BlobArtifacts/, the full path is the destination layout under the channel's blob feed.
4. Calls Arcade's standard publish-build-assets.yml job, which registers the build with BAR.

A small MSBuild target (WriteDotnetupVersionFile in dotnetup.csproj) emits dotnetup.version.txt next to each published binary so the staging job has an authoritative source for the Arcade-composed $(Version) SemVer (no MSBuild file parsing in the pipeline).

End-to-end mechanics validated

Validated in two stages:

1. Experiment branch — promoted BAR build 314208 to General Testing (promotion build 2974290). All 16 binary/checksum assets landed at https://ci.dot.net/dev/dotnetup/0.1.3-preview.4.26263.3/... with HTTP 200 anonymous access.

2. This branch — BAR build 314269 (CI build 2974542) registered 17 assets at dotnetup/0.1.3-preview.4.26263.5/... — identical structure to the experiment build, confirming the cleanups (squashed history, dropped manual gate, robust version-file lookup) didn't regress anything. Channel attachment deferred until dotnet/arcade#16813 merges.

Asset list for build 314208:

File	Size
dotnetup-win-x64.exe	14.4 MB
dotnetup-win-arm64.exe	15.0 MB
dotnetup-linux-x64	14.1 MB
dotnetup-linux-arm64	14.6 MB
dotnetup-linux-musl-x64	14.1 MB
dotnetup-linux-musl-arm64	14.6 MB
dotnetup-osx-x64	14.0 MB
dotnetup-osx-arm64	13.3 MB

(Plus matching .sha512 checksums.)

Companion changes

This PR is the fourth in a coordinated series:

#	Change	Status
1	maestro-configuration#61048 — create dotnetup Daily channel	✅ merged
2	dotnet/arcade#16813 — register channel publishing config (feeds + aka.ms patterns)	open
3	maestro-configuration#61053 — default-channel mapping for dotnet/sdk@release/dnup → dotnetup Daily	open
4	This PR	open

If this PR merges before the arcade and default-channel-mapping PRs above, every CI build will register with BAR but no automatic publishing will happen — manual darc add-build-to-channel is the workaround. Once all four are merged, every CI build of release/dnup will auto-publish to ci.dot.net/public/dotnetup/<SemVer>/ and refresh the aka.ms/dotnet/dotnetup/daily/<file> shortlinks.

What's intentionally NOT in this PR

• NuGet package routing through BAR (per Matt Mitchell's defense-in-depth recommendation): keeping the existing 1ES.PublishNuget@1 direct-push of Microsoft.Dotnet.Installation for now. Including it here would mean either a publishing gap (if direct push is removed before automatic promotion is wired up) or double-publish (if both run simultaneously). Better as a follow-up PR sequenced after auto-promotion is confirmed working end-to-end.
• Switching the get-dotnetup.{sh,ps1} install scripts to anonymous URLs: the current scripts use az to download pipeline artifacts. Once builds are flowing to ci.dot.net/public/dotnetup/... and aka.ms/dotnet/dotnetup/daily/... links are live, those scripts can drop the az requirement. Follow-up PR.
• v4 publishing pipeline migration — Matt offered to do this post-merge for ~20min savings on the staging job.

[Copilot]

Pull request overview

Adds Build Asset Registry (BAR) registration for non-PR release/dnup dotnetup builds by staging standalone executables/checksums into the expected BlobArtifacts/ layout, generating a v3 MergedManifest.xml, and invoking Arcade’s standard publish-build-assets job so Maestro can later promote/upload to channel-based blob feeds.

Changes:

• Emit dotnetup.version.txt during dotnet publish so pipelines can consume the Arcade-computed $(Version) without parsing MSBuild files.
• Include dotnetup.version.txt in each per-RID dotnetup-standalone-* pipeline artifact (Windows + Unix staging).
• Add a new staging + BAR-registration job template and wire it into .vsts-dnup-ci.yml as a publish_to_bar stage for non-PR builds.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/Installer/dotnetup/dotnetup.csproj	Adds an MSBuild target to write dotnetup.version.txt into the publish output.
eng/pipelines/templates/jobs/dotnetup/dotnetup-publish-to-bar.yml	New job template that downloads per-RID standalone artifacts, stages a flat BlobArtifacts/ layout, generates MergedManifest.xml, and runs Arcade BAR registration.
eng/pipelines/templates/jobs/dotnetup/dotnetup-executables.yml	Updates per-RID staging to include dotnetup.version.txt in the standalone artifacts used by BAR staging.
.vsts-dnup-ci.yml	Adds the publish_to_bar stage (non-PR) that depends on all per-RID executable stages and runs the BAR registration template.

[dsplaisted]

Marking draft while we evaluate an alternative approach. Per Matt's feedback on the email thread, exploring switching dotnetup to use standard Arcade primitives (build.cmd -pack -sign -publish with /p:Projects=dotnetup.slnf) instead of the bespoke pipeline this PR builds on. Will pick this back up depending on how that exploration goes.