Better UX for generating primary keys using bespoke inputs for hash files

[PaulRBerg]

Problem

Generating the primary key is a little difficult when a lot of files need to be hashed. Here's an example from our repo:

key: foo-${{ hashFiles('yarn.lock') }}-${{ hashFiles('/**/*.{js,json,jsx,ts,tsx}') }}

That's a rather verbose line of code.

Solution

Since the vast majority of users need to use hashFiles, enable a new input parameter called key-hash-files (name TBD) that allows users to specify paths an an array, e.g.

- uses: "actions/cache@v4"
      id: "cache-step"
      with:
          key-prefix: "foo-"
          key-hash-files:
              - `yarn.lock`
              - `/**/*.{js,json,jsx,ts,tsx}`

And then, each input in the array would be passed as an input to hashFiles, and the resulting hash would be added to the key name. Each hash would be prefixed by -.