How to get access token for a github app installed in a different organization?

[harshtrivedi134]

I am currently working on developing a GitHub workflow utilizing Octokit. My goal is to synchronize files from one repository, Repo A (hosted on github.com), to another repository, Repo B (hosted on GitHub Enterprise). These repositories belong to different organizations.

The workflow is running within Repo A, and I am attempting to obtain the access token of the GitHub App installed in the organization of Repo B. My question is: How can I achieve this using the app-client?
Thank you in advance for your help!

[gr2m]

If you know the repository, you can use the GET /repos/{owner}/{repo}/installation endpoint

const { data: installationRepoA } = await app.octokit.request("GET /repos/{owner}/{repo}/installation", { owner: ownerA, repo: repoA })
const { data: installationRepoB } = await app.octokit.request("GET /repos/{owner}/{repo}/installation", { owner: ownerB, repo: repoB })

const installactionOctokitA = await app.getInstallationOctokit(installationRepoA.id)
const installactionOctokitB = await app.getInstallationOctokit(installationRepoA.id)

// use `installactionOctokitA` to read the source file, and `installactionOctokitB` to write the target file

[harshtrivedi134]

Thanks! @gr2m
So basiscaly the default app would only provide pre-authenticated client for current repository & org where the workflow/action is running ?

const { App } = require('octokit');
const app = new App({ appId, privateKey });
const octokit = await app.getInstallationOctokit(installationId);

[gr2m]

no the app instance can authenticate as any of its installations, it doesn't matter where the code is run. You can also use the create-github-app-token action for this use case if you like: https://github.com/actions/create-github-app-token#create-a-token-for-all-repositories-in-another-owners-installation

[harshtrivedi134]

I was trying out the create-github-app-token I think it defaults to the https://api.github.com/users/{owner}/installation api. In my case it is github enterprise and the HOSTNAME would be different. I was wondering whether there would be an input to this action that would allow us to override baseUrl but I don't think such attribute exists.

[gr2m]

It's not yet implemented, we'd need to add something like this: https://github.com/tibdex/github-app-token/blob/3eb77c7243b85c65e84acfa93fdbac02fb6bd532/action.yml#L8C1-L10C35. I thought we had an open issue for it but doesn't look like it

If you could create an issue and explain your use that'd be fabulous, I can look into it this week

[harshtrivedi134]

@gr2m Awesome! I have created an issue - #2569 actions/create-github-app-token#77
Looking forward to it!