Suggest extracting prerelease tag resolution into a testable function for #1657

[Copilot]

PR #1657 fixes the prerelease channel of copilot-cli by replacing git ls-remote | tail -1 with a sort -V pipeline. Review feedback asks that the pipeline be moved into a function and covered by a regression test.

This PR is advisory only — no repository changes were committed. Recommended changes for #1657:

• Extract resolve_prerelease_version() in src/copilot-cli/install.sh that reads git ls-remote --tags output from stdin (for tests) or runs it against a repo URL passed as $1 (for production), then pipes through awk | sed | grep -E '^v[0-9]+\.[0-9]+\.[0-9]+(-[0-9]+)?$' | sort -V | tail -n1.
• Update the prerelease branch of install_using_github to call resolve_prerelease_version "https://github.com/github/copilot-cli".
• Add test/copilot-cli/scenarios.json registering a resolve_prerelease_version scenario on mcr.microsoft.com/devcontainers/base:ubuntu.
• Add test/copilot-cli/resolve_prerelease_version.sh that sources only the function (via awk '/^resolve_prerelease_version\(\)/,/^}$/' + eval, avoiding the installer's root check) and asserts ordering against a hermetic fixture covering the regression cases:
  • v1.0.45 > v1.0.9 (the original bug).
  • v1.0.45-10 > v1.0.45-2 (numeric prerelease suffix).
  • Peeled refs (^{}) and non-vX.Y.Z tags are filtered out.

Function snippet:

resolve_prerelease_version() {
    local repo_url="${1:-}"
    if [ -n "${repo_url}" ]; then
        git ls-remote --tags "${repo_url}"
    else
        cat
    fi \
      | awk '{print $2}' | sed 's|refs/tags/||' \
      | grep -E '^v[0-9]+\.[0-9]+\.[0-9]+(-[0-9]+)?$' \
      | sort -V | tail -n1
}

Run locally with:

devcontainer features test -f copilot-cli \
  --skip-autogenerated --filter "resolve_prerelease_version" .

Stdin-driven design keeps the regression test hermetic (no network) and pins both the lexicographic-sort bug and the prerelease-suffix ordering against future regressions.

Original prompt

Check the comment here #1657 (comment) and suggest solution. Provide code snippets

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