It would be nice if setup-node understood an .nvmrc file (even if it does not use nvm under the hood, the idea is the node-version is just the contents of the file).

If GitHub Actions as a whole could read the contents of a file as part of an expression, I could do something like

uses: setup-node@v1
with:
  node-version: {{ contents(.nvmrc) }}

But I don't know where to log that type of feature request!

Perhaps '.nvmrc' could be used as a special placeholder, so that:

uses: setup-node@v1
with:
  node-version: '.nvmrc'

Instructs this action to read the contents and treat the contents as the desired version?