Fix detached-SHA versioning: branch input + git checkout -B (completes IGNORE_GITHUB_REF)

[ptr727]

Problem (caught by Copilot on #199)

#198 switched to IGNORE_GITHUB_REF=true (NBGV versions from the checked-out branch) and dropped the branch input. But build-nugetlibrary checks out a pinned commit SHA (detached HEAD) to recompute the package version. On a detached HEAD NBGV sees no branch → classifies as prerelease → the main leg builds a 1.4.x-g<sha> package mismatching its clean 1.4.x release tag.

Verified with the nbgv tool: detached at main's commit + IGNORE_GITHUB_REF → PublicRelease=False, 1.4.3-gef05e9edc1.

Fix

Re-add the branch input and, after checkout, git checkout -B <branch> so NBGV sees the logical branch even from a detached SHA (keeping IGNORE_GITHUB_REF). Re-thread branch to both get-version callers.

Verified in CI (detached-SHA path via build-release-task smoke)

Built nupkg from the detached build-nugetlibrary checkout:

leg	built package
main	ptr727.LanguageTags.1.4.3.nupkg (clean ✅)
develop	ptr727.LanguageTags.1.4.4-gf2560a8e4c.nupkg (prerelease ✅)

Both legs now version correctly from a detached checkout, matching the release tag.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Updates the reusable GitHub Actions workflows to ensure Nerdbank.GitVersioning (NBGV) computes the correct public vs prerelease version even when a job checks out a pinned commit SHA (detached HEAD), which is critical for producing stable main packages that match release tags.

Changes:

• Re-introduces a branch input to get-version-task.yml and creates a local branch at HEAD (git checkout -B <branch>) when provided, so NBGV can classify versions correctly under IGNORE_GITHUB_REF=true.
• Threads the branch input through build-release-task.yml and build-nugetlibrary-task.yml when calling get-version-task.yml.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
.github/workflows/get-version-task.yml	Adds a branch input and pins a logical local branch in detached-SHA checkouts so NBGV version classification matches the intended branch.
.github/workflows/build-release-task.yml	Passes inputs.branch through to get-version-task.yml to keep version computation consistent for release builds.
.github/workflows/build-nugetlibrary-task.yml	Passes inputs.branch through to get-version-task.yml so pinned-SHA build jobs still version as main vs prerelease correctly.