Fix support for requesting a custom media type

[timrogers]

This action supports passing a custom mediaType, but this doesn't actually work. The action receives a string, but octokit/endpoint.js [expects][1] to be passed an object with format and/or previews keys.

Trying to pass a mediaType value as suggested in the action.yml leads to a Cannot read property 'map' of undefined error which comes from [endpoint.js's merge function][2] which is assuming that the passed mediaType will be an object with properties.

This fixes the issue by taking the value passed in as mediaType and sending it to endpoint.js as mediaType.format.

There are other potential approaches we could take to this, for example:

• supporting a more basic accept option instead for a raw header
• accepting mediaTypeFormat and mediaTypePreviews (or similar)

Fixes https://github.com/octokit/request-action/issues/175.

[1]: https://github.com/octokit/endpoint.js#endpointroute-options-or-endpointoptions [2]: https://github.com/octokit/endpoint.js/blob/8266fc12765e94cb966d5104a375631b4efb0dbf/src/merge.ts#L35-L37

[gr2m]

You can pass mediaType like this

          mediaType: | # The | is significant!
            format: raw

I'd suggest we add an example to the README instead of doing the code change?

[timrogers]

You can pass mediaType like this

          mediaType: | # The | is significant!
            format: raw

I'd suggest we add an example to the README instead of doing the code change?

Interesting! I didn't know you could pass an object using that format. Let's update the README as you suggest.

[gr2m]

I didn't know you could pass an object using that format

it only works because of the way we read out the parameters in this action, it's not a built-in GitHub Actions feature.