use showFileAtRef instead of readFileBase64

src/create-pull-request.ts

@@ -211,6 +211,7 @@ export async function createPullRequest(inputs: Inputs): Promise<void> {
         const stashed = await git.stashPush(['--include-untracked'])
         await git.checkout(inputs.branch)
         const pushSignedCommitsResult = await ghBranch.pushSignedCommits(
+          git,
           result.branchCommits,
           result.baseCommit,
           repoPath,

src/github-helper.ts

@@ -1,6 +1,6 @@
 import * as core from '@actions/core'
 import {Inputs} from './create-pull-request'
-import {Commit} from './git-command-manager'
+import {Commit, GitCommandManager} from './git-command-manager'
 import {Octokit, OctokitOptions, throttleOptions} from './octokit-client'
 import pLimit from 'p-limit'
 import * as utils from './utils'
@@ -220,6 +220,7 @@ export class GitHubHelper {
   }
 
   async pushSignedCommits(
+    git: GitCommandManager,
     branchCommits: Commit[],
     baseCommit: Commit,
     repoPath: string,
@@ -233,6 +234,7 @@ export class GitHubHelper {
     }
     for (const commit of branchCommits) {
       headCommit = await this.createCommit(
+        git,
         commit,
         headCommit,
         repoPath,
@@ -244,6 +246,7 @@ export class GitHubHelper {
   }
 
   private async createCommit(
+    git: GitCommandManager,
     commit: Commit,
     parentCommit: CommitResponse,
     repoPath: string,
@@ -272,7 +275,7 @@ export class GitHubHelper {
                 const {data: blob} = await blobCreationLimit(() =>
                   this.octokit.rest.git.createBlob({
                     ...repository,
-                    content: utils.readFileBase64([repoPath, path]),
+                    content: git.showFileAtRef(commit.sha, path),
                     encoding: 'base64'
                   })
                 )