Skip release branches for same-milestone Skia updates

[mattleibow]

Description

Make the merge-skia-update landing helper compare the parent PR's base and head chrome_milestone values before preserving a release line. Previously, every Skia update targeting main derived and offered to create a release branch, including same-milestone bug-fix syncs such as m153 → m153.

Same-milestone updates now exit without checking or creating release refs. Real milestone bumps still derive the previous release/A.B.x line from the base commit, and the push path rechecks the parent head SHA before writing refs. Later merge guidance and post-merge verification now consistently use the resolved parent base branch, so servicing updates do not incorrectly refer to main.

Related issues

N/A.

Required skia PR

None.

Areas affected

• Managed API (binding/)
• Native / C API (externals/skia/src/c, include/c)
• Generated P/Invoke bindings
• Native dependency or Skia update (libpng, HarfBuzz, FreeType, zlib, milestone bump, …)
• Views & integrations (MAUI, Uno, WPF, WinUI, Blazor, …)
• Rendering output / visual behavior
• Performance
• Tests
• Build, packaging, or CI
• Documentation or samples

Changes

None — automation-only; no public API or observable product behavior changes.

Testing

• Added a merge-skia-update behavioral eval for same-milestone updates targeting main.
• Updated the merge-handoff eval to require CI guidance for the resolved parent base branch rather than assuming main.
• Ran the updated helper against mono/SkiaSharp [skia-sync] Merge upstream chrome/m153 bug fixes #4927 (main → skia-sync/m153); it reported Same-milestone sync: m153 -> m153 and created no refs.
• Parsed the updated PowerShell script and eval JSON, and audited the skill for remaining hard-coded post-merge main assumptions.

Checklist

• Tests added or updated (if omitted, explain why above)
• Changes above lists all public API and behavioral changes (or "None.")
• New/changed public API? N/A — no public API changes
• Native change? N/A — no native changes

[github-actions]

📦 Try the packages from this PR

Warning

Do not run these scripts without first reviewing the code in this PR.

Step 1 — Download the packages

bash / macOS / Linux:

curl -fsSL https://raw.githubusercontent.com/mono/SkiaSharp/main/scripts/get-skiasharp-pr.sh | bash -s -- 4948

PowerShell / Windows:

iex "& { $(irm https://raw.githubusercontent.com/mono/SkiaSharp/main/scripts/get-skiasharp-pr.ps1) } 4948"

Step 2 — Add the local NuGet source

dotnet nuget add source ~/.skiasharp/hives/pr-4948/packages --name skiasharp-pr-4948

More options

Option	Description
--successful-only / -SuccessfulOnly	Only use successful builds
--force / -Force	Overwrite previously downloaded packages
--list / -List	List available artifacts without downloading
--build-id ID / -BuildId ID	Download from a specific build

Or download manually from Azure Pipelines — look for the nuget artifact on the build for this PR.

Remove the source when you're done:

dotnet nuget remove source skiasharp-pr-4948

[github-actions]

📊 SkiaSharp benchmarks — PR #4948

⭐ this PR (full source build) vs 🌙 nightly · Linux · Windows · macOS

Informational only — this never blocks the PR. 🟢 faster / less allocation · 🔴 slower / more allocation; moves under 5% are hidden as noise.

⏱️ Times are raw BenchmarkDotNet means, and the ⭐ PR and baseline legs run on separate CI runners, so microbenchmarks can swing run-to-run — treat small time deltas as noise. Allocations are deterministic and the reliable signal. The interactive perf-dashboard (linked below) applies smoothing for the trend view.

Highlights

⏱️ Time — 🔴 1 slower · 🟢 1 faster

• 🔴 ColorParseBenchmark.Parse(Iterations: 1000) · macOS · 69.25 µs → 78.62 µs (+14%)
• 🟢 ColorParseBenchmark.Parse(Iterations: 1000) · Windows · 75.54 µs → 67.22 µs (-11%)

Full per-OS benchmark deltas

Windows

⏱️ Time (vs 🌙 nightly 4.152.0-nightly.26431.1)

Benchmark	baseline	this PR	Δ
ColorParseBenchmark.Parse(Iterations: 1000)	75.54 µs	67.22 µs	🟢 -11%

macOS

⏱️ Time (vs 🌙 nightly 4.152.0-nightly.26431.1)

Benchmark	baseline	this PR	Δ
ColorParseBenchmark.Parse(Iterations: 1000)	69.25 µs	78.62 µs	🔴 +14%

📈 Full interactive perf-dashboard & run details →

[github-actions]

📖 Documentation Preview

The documentation for this PR has been deployed and is available at:

🔗 View Staging Site
🔗 View Staging Docs
🔗 View Staging Gallery (Blazor)
🔗 View Staging Gallery (Uno Platform)
🔗 View Staging SkiaFiddle

This preview will be updated automatically when you push new commits to this PR.

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