Implementing copilot skill for version tag management

.github/skills/sync-upstream-tags/SKILL.md

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+---
+name: sync-upstream-tags
+description: Compare local release tags with git/git tags and create+push each missing version tag in ascending order.
+---
+
+# Sync Upstream Git Release Tags
+
+Use this skill when you need to synchronize this repository's release tags with upstream Git releases.
+
+## Steps
+
+1. Identify the latest local semantic version tag (`X.Y.Z`) in this repository.
+2. Fetch upstream release tags from `https://github.com/git/git/tags`.
+3. Compute missing semantic version tags not present locally.
+4. Process missing tags in ascending version order (oldest to newest).
+5. For each missing tag, run:
+   - `git tag <version>`
+   - `git push origin <version>`
+6. Stop immediately if any command fails, and report which tag failed.
+
+## Run
+
+```bash
+bash .github/skills/sync-upstream-tags/scripts/sync-upstream-tags.sh
+```
+
+## Verify
+
+- [ ] Missing tags were handled from oldest to newest
+- [ ] Every created tag was pushed individually
+- [ ] No non-semver tags were created

.github/skills/sync-upstream-tags/scripts/sync-upstream-tags.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+UPSTREAM_REPO_URL="https://github.com/git/git.git"
+SEMVER_PATTERN='^[0-9]+\.[0-9]+\.[0-9]+$'
+
+mapfile -t local_tags < <(git tag --list | grep -E "$SEMVER_PATTERN" | sort -V || true)
+mapfile -t upstream_tags < <(
+  git ls-remote --tags --refs "$UPSTREAM_REPO_URL" \
+    | awk '{print $2}' \
+    | sed 's#refs/tags/##' \
+    | sed 's/^v//' \
+    | grep -E "$SEMVER_PATTERN" \
+    | sort -uV
+)
+
+latest_local_tag=""
+if ((${#local_tags[@]} > 0)); then
+  latest_local_tag="${local_tags[-1]}"
+fi
+
+printf 'Latest local semver tag: %s\n' "${latest_local_tag:-<none>}"
+
+declare -A local_tag_lookup=()
+for tag in "${local_tags[@]}"; do
+  local_tag_lookup["$tag"]=1
+done
+
+missing_tags=()
+for tag in "${upstream_tags[@]}"; do
+  if [[ -z "${local_tag_lookup[$tag]:-}" ]]; then
+    missing_tags+=("$tag")
+  fi
+done
+
+if ((${#missing_tags[@]} == 0)); then
+  echo "No missing upstream semver tags found."
+  exit 0
+fi
+
+printf 'Missing tags to create/push (%d): %s\n' "${#missing_tags[@]}" "${missing_tags[*]}"
+
+for tag in "${missing_tags[@]}"; do
+  echo "Creating tag: $tag"
+  git tag "$tag"
+
+  echo "Pushing tag: $tag"
+  git push origin "$tag"
+done
+
+echo "Tag synchronization complete."