Implement gitea-pr merge

bin/gitea-pr

@@ -132,7 +132,24 @@ case "$subcommand" in
         echo "$json" | jq -r '.[] | select(.body != "") | "[\(.user.login) @ \(.submitted_at) — \(.state)]\n\(.body)\n"'
         ;;
     merge)
-        echo "merge: not yet implemented" >&2
-        exit 1
+        pr_number="${1:-}"
+        if [ -z "$pr_number" ]; then
+            echo "Usage: gitea-pr merge PR_NUMBER" >&2
+            exit 1
+        fi
+
+        response=$(curl -sS -w '\n%{http_code}' -X POST "${GITEA_API}/repos/${owner}/${repo}/pulls/${pr_number}/merge" \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            -H "Content-Type: application/json" \
+            -d '{"Do": "merge"}')
+        http_code=$(echo "$response" | tail -1)
+        json=$(echo "$response" | sed '$d')
+
+        if [ "$http_code" -lt 200 ] || [ "$http_code" -ge 300 ]; then
+            echo "Failed to merge PR #${pr_number} (HTTP $http_code):" >&2
+            echo "$json" >&2
+            exit 1
+        fi
+        echo "Merged PR #${pr_number}"
         ;;
 esac