[BUG] Cannot just install cog anymore

cwrau

**Describe the bug** Before v4 one could use this action to just install cog to be used later by specifying `check: false`, now `command` is required. **To Reproduce** **Expected behavior** There should be a possibility to just install cog without running it, maybe a `install-only: true` flag? **Additional context** Current workaround is setting `command: help`...

joshua-clayton

I tried the latest with install-only. My cog commands failed because the git user.name and user.email are not set. I've opened a PR to fix this, and in the meantime, I'm using command: "--version"