Use positional argument instead of deprecated --prompt flag #453

Summary

The Gemini CLI has deprecated the --prompt (-p) flag in favor of positional arguments. This action currently uses:

gemini --yolo --prompt "${PROMPT}" --output-format json

This produces a deprecation warning in CI logs:

The --prompt (-p) flag has been deprecated and will be removed in a future version. Please use a positional argument for your prompt. See gemini --help for more information.

Suggested Fix

Change the CLI invocation to use a positional argument:

gemini --yolo --output-format json "${PROMPT}"

Or pipe via stdin if multiline prompts are a concern:

echo "${PROMPT}" | gemini --yolo --output-format json

Impact

• Currently: Warning noise in CI logs
• Future: Will break when the flag is removed

Environment

• Action version: v0.1.20
• Gemini CLI: latest (as of 2026-01-29)