Pandoc is kind of neat but why not just use markdown?
markdown input.md > output.html
It is a personal preference but I would rather know one tool they is more versatile (especially for such a task)
Why would you want to constantly recompile documents every time you make an edit to them? Why would you want to juggle two files for every document you produce?
For what it's worth, this is the problem GitLab Pages solves. A simple "git push" to a properly to figured repo will rebuild and redeploy your static site, the actual html output doesnt go into the repo.
This is for people who don't want to setup and manage a deployment pipeline hooked up to a git source code repo.