ci/github-script/prepare: init from actions/get-merge-commit

This just moves the code over to ci/github-script to make it easy to
test and iterate on locally.

The name `prepare` is chosen, because the script will be extended with
the other steps from "PR / prepare" next.

.github/actions/get-merge-commit/action.yml

@@ -35,50 +35,11 @@ runs:
       uses: actions/github-script@60a0d83039c74a4aee543508d2ffcb1c3799cdea # v7.0.1
       with:
         script: |
-          for (const retryInterval of [5, 10, 20, 40, 80]) {
-            console.log("Checking whether the pull request can be merged...")
-            const prInfo = (await github.rest.pulls.get({
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              pull_number: context.payload.pull_request.number
-            })).data
-
-            if (prInfo.state != 'open') throw new Error ("PR is not open anymore.")
-
-            if (prInfo.mergeable == null) {
-              console.log(`GitHub is still computing whether this PR can be merged, waiting ${retryInterval} seconds before trying again...`)
-              await new Promise(resolve => setTimeout(resolve, retryInterval * 1000))
-              continue
-            }
-
-            let mergedSha, targetSha
-
-            if (prInfo.mergeable) {
-              console.log("The PR can be merged.")
-
-              mergedSha = prInfo.merge_commit_sha
-              targetSha = (await github.rest.repos.getCommit({
-                owner: context.repo.owner,
-                repo: context.repo.repo,
-                ref: prInfo.merge_commit_sha
-              })).data.parents[0].sha
-            } else {
-              console.log("The PR has a merge conflict.")
-
-              mergedSha = prInfo.head.sha
-              targetSha = (await github.rest.repos.compareCommitsWithBasehead({
-                owner: context.repo.owner,
-                repo: context.repo.repo,
-                basehead: `${prInfo.base.sha}...${prInfo.head.sha}`
-              })).data.merge_base_commit.sha
-            }
-
-            console.log(`Checking the commits:\nmerged:${mergedSha}\ntarget:${targetSha}`)
-            core.setOutput('mergedSha', mergedSha)
-            core.setOutput('targetSha', targetSha)
-            return
-          }
-          throw new Error("Not retrying anymore. It's likely that GitHub is having internal issues: check https://www.githubstatus.com.")
+          require('./ci/github-script/prepare.js')({
+            github,
+            context,
+            core,
+          })
 
     - if: inputs.merged-as-untrusted && (inputs.mergedSha || steps.commits.outputs.mergedSha)
       # Would be great to do the checkouts in git worktrees of the existing spare checkout instead,

.github/workflows/codeowners-v2.yml

@@ -53,7 +53,9 @@ jobs:
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
         with:
-          sparse-checkout: .github/actions
+          sparse-checkout: |
+            .github/actions
+            ci/github-script
       - name: Check if the PR can be merged and checkout the merge and target commits
         uses: ./.github/actions/get-merge-commit
         with:

.github/workflows/pr.yml

@@ -34,6 +34,7 @@ jobs:
         with:
           sparse-checkout: |
             .github/actions
+            ci/github-script
             ci/supportedBranches.js
             ci/supportedSystems.json
       - name: Check if the PR can be merged and get the test merge commit

ci/github-script/prepare.js

@@ -0,0 +1,46 @@
+module.exports = async function ({ github, context, core }) {
+  for (const retryInterval of [5, 10, 20, 40, 80]) {
+    console.log("Checking whether the pull request can be merged...")
+    const prInfo = (await github.rest.pulls.get({
+      owner: context.repo.owner,
+      repo: context.repo.repo,
+      pull_number: context.payload.pull_request.number
+    })).data
+
+    if (prInfo.state != 'open') throw new Error ("PR is not open anymore.")
+
+    if (prInfo.mergeable == null) {
+      console.log(`GitHub is still computing whether this PR can be merged, waiting ${retryInterval} seconds before trying again...`)
+      await new Promise(resolve => setTimeout(resolve, retryInterval * 1000))
+      continue
+    }
+
+    let mergedSha, targetSha
+
+    if (prInfo.mergeable) {
+      console.log("The PR can be merged.")
+
+      mergedSha = prInfo.merge_commit_sha
+      targetSha = (await github.rest.repos.getCommit({
+        owner: context.repo.owner,
+        repo: context.repo.repo,
+        ref: prInfo.merge_commit_sha
+      })).data.parents[0].sha
+    } else {
+      console.log("The PR has a merge conflict.")
+
+      mergedSha = prInfo.head.sha
+      targetSha = (await github.rest.repos.compareCommitsWithBasehead({
+        owner: context.repo.owner,
+        repo: context.repo.repo,
+        basehead: `${prInfo.base.sha}...${prInfo.head.sha}`
+      })).data.merge_base_commit.sha
+    }
+
+    console.log(`Checking the commits:\nmerged:${mergedSha}\ntarget:${targetSha}`)
+    core.setOutput('mergedSha', mergedSha)
+    core.setOutput('targetSha', targetSha)
+    return
+  }
+  throw new Error("Not retrying anymore. It's likely that GitHub is having internal issues: check https://www.githubstatus.com.")
+}

ci/github-script/run

@@ -39,6 +39,17 @@ async function run(action, owner, repo, pull_number, dry = true) {
   })
 }
 
+program
+  .command('prepare')
+  .description('Prepare relevant information of a pull request.')
+  .argument('<owner>', 'Owner of the GitHub repository to check (Example: NixOS)')
+  .argument('<repo>', 'Name of the GitHub repository to check (Example: nixpkgs)')
+  .argument('<pr>', 'Number of the Pull Request to check')
+  .action(async (owner, repo, pr) => {
+    const prepare = (await import('./prepare.js')).default
+    run(prepare, owner, repo, pr)
+  })
+
 program
   .command('commits')
   .description('Check commit structure of a pull request.')