Allow to provide custom LHCI config

[szimek]

This PR introduces changes that allow one to provide a partial custom LHCI config that gets merged with the default one provided in entrypoint.sh file and fixes #20.

It's a bit of a wip, but I wanted to get some feedback first. Things that are missing:

• make the path configurable (the default is set to .lighthouserc.yml)
• update README.md file
• update Dockerfile to use the updated base image, once it's published

It's also possible to overwrite some of the other inputs (e.g. LHCI scores) with this config, which might be a bit confusing.

I tested it with act and it works. I also pushed the new base Docker image that includes yq to szimek/lighthouse-ci-action:1.1.0.

[charlespwd]

I think I'd just use .lighthouserc.yml as default since that's the default for LHCI. Probably better for us to handle this complexity. Would make our code slightly more complicated, but we're taking that complexity away from the devs.

Maybe something like:

default_config="$(mktemp XXXXX.yml)"
cat <<- EOF > $default_config
  ...
EOF

if [[ -f ".lighthouserc.yml" ]]; then
  yq eval-all '...' $default_config .lighthouserc.yml > .lighthouserc.yml.tmp
  mv .lighthouserc.yml.tmp .lighthouserc.yml
else
  mv $default_config .lighthouserc.yml
else

[szimek]

Much better!

I'd just make sure that it's clearly explained in the README that it doesn't have to be the complete config.

[charlespwd]

It's also possible to overwrite some of the other inputs (e.g. LHCI scores) with this config, which might be a bit confusing.

I think that's OK. If you're overwriting them, then it's really on you :P.

I think we can fix that with some kind of "Advanced Usage" docs that shows the default configuration and how you can change that.

[szimek]

@charlespwd I've just pushed an updated version.

One thing that I found a bit confusing is the default value for inputs in action.yml - I thought that when the default value is set, it will cause the respective environment variable to be set up with this default value. It looks like it's not the case, though.

Anyway, while working on it, I realized that one can overwrite any LHCI configuration setting with environment variables, so it's already possible to modify the default upload config with:

jobs:
  lhci:
    name: Lighthouse
    runs-on: ubuntu-latest
    steps:
       - name: Lighthouse
         ...
         env:
           LHCI_UPLOAD__TARGET: lhci
           LHCI_UPLOAD__SERVER_BASE_URL: ...
           LHCI_UPLOAD__TOKEN: ...
           LHCI_UPLOAD__BASIC_AUTH__USERNAME: ...
           LHCI_UPLOAD__BASIC_AUTH__PASSWORD: ...

Maybe it's not very convenient, but possible.