Prerelease fix (#215 GITHUB_REF override) is ineffective — GITHUB_REF is reserved; use IGNORE_GITHUB_REF

[ptr727]

Summary

The fix for #213 (PR #215) restores the develop leg's prerelease tag by overriding GITHUB_REF in the nbgv step env:. This does not work. GITHUB_REF is a GitHub-reserved variable that a step-level env: cannot reliably override — the runner re-injects the dispatch ref. NBGV's GitHub Actions cloud-build provider reads GITHUB_REF for BuildingRef, so on a publish dispatched from main the develop leg is still classified as the public ref and publishes a clean (stable) version.

Evidence (CI)

First real publish after #215 landed in a derived repo — the develop leg's nbgv step:

GITHUB_REF: refs/heads/develop      # the step-env override (as configured)
"BuildingRef": "refs/heads/main"    # NBGV still saw the dispatch ref
"PublicRelease": true
"SemVer2": "1.4.2"                   # clean, no -g suffix

The validate-release gate correctly blocked the publish (so no bad package shipped), but the develop prerelease leg never publishes.

Root cause

GITHUB_REF is reserved; overriding it via step env: is unsupported (GitHub: "Setting an environment variable with the GITHUB_ prefix may result in unexpected behavior"). NBGV reads it for BuildingRef:

// src/NerdBank.GitVersioning/CloudBuildServices/GitHubActions.cs
private static string BuildingRef => IgnoreGitHubRef ? null : Environment.GetEnvironmentVariable("GITHUB_REF");
private static bool IgnoreGitHubRef => string.Equals(Environment.GetEnvironmentVariable("IGNORE_GITHUB_REF"), "true", StringComparison.OrdinalIgnoreCase);

Fix

NBGV versions from the checked-out branch; its cloud provider only overrides that with GITHUB_REF. Each matrix leg already checks out its own branch (Switched to a new branch 'develop'). Set NBGV's own IGNORE_GITHUB_REF=true so it ignores the CI ref and uses the checked-out branch:

      - name: Run Nerdbank.GitVersioning tool step
        id: nbgv
        uses: dotnet/nbgv@master
        env:
          IGNORE_GITHUB_REF: true

Drop the branch input/threading added to get-version-task.yml and its callers for the (ineffective) GITHUB_REF override; the validate-release entry gate stays as the backstop.

Verified (CI probe, real dotnet/nbgv action)

checkout	IGNORE_GITHUB_REF	PublicRelease	SemVer2
develop	true	False	1.4.2-g14f645dfd9
main	true	True	1.4.3
main	false	False	1.4.3-g… (reproduces the bug)

Supersedes #215. Found in a derived repo's first real publish + a CI probe.

[ptr727]

Fixed on develop via #222 (36f7eeb): NBGV IGNORE_GITHUB_REF (supersedes the ineffective #215 GITHUB_REF override; validate-release gate retained as backstop). Ships on the next develop → main release.

[ptr727]

Important refinement — IGNORE_GITHUB_REF=true alone is insufficient; it must be paired with re-adding the branch input and a git checkout -B <branch> step.

Reason: with IGNORE_GITHUB_REF, NBGV versions from the checked-out git branch. build-nugetlibrary (and any caller pinning to a commit SHA) checks out a detached HEAD, where NBGV sees no branch and classifies every leg as prerelease — so the main leg builds a X.Y.Z-g<sha> package that mismatches its clean X.Y.Z release tag.

Verified with the nbgv tool:

state	result
detached at main SHA + IGNORE_GITHUB_REF	PublicRelease=False, 1.4.3-gef05e9edc1 (wrong)
detached + IGNORE_GITHUB_REF + git checkout -B main	PublicRelease=True, 1.4.3 (correct)

Complete fix

get-version-task.yml: keep the branch input; after checkout, force a local branch so NBGV sees the logical branch from a detached SHA:

      - name: Checkout code step
        uses: actions/checkout@... 
        with:
          ref: ${{ inputs.ref }}
          fetch-depth: 0

      - name: Pin logical branch step
        if: ${{ inputs.branch != '' }}
        env:
          BRANCH: ${{ inputs.branch }}
        run: git checkout -B "$BRANCH"

      - name: Run Nerdbank.GitVersioning tool step
        id: nbgv
        uses: dotnet/nbgv@master
        env:
          IGNORE_GITHUB_REF: true

Thread branch to both get-version callers (build-release-task and build-nugetlibrary-task).

CI-verified (detached build-nugetlibrary path)

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

(The cleaner long-term alternative is to compute the version once and thread it into build-nugetlibrary rather than recomputing on a detached checkout — that removes the dual-get-version divergence entirely.)