Add parameter to control version script (#23)

* Add version script

* Run build

Co-authored-by: mitchellhamilton <mitchell@hamil.town>

README.md

@@ -64,7 +64,6 @@ jobs:
           # This makes Actions fetch all Git history so that Changesets can generate changelogs with the correct commits
           fetch-depth: 0
 
-
       - name: Setup Node.js 12.x
         uses: actions/setup-node@master
         with:
@@ -82,3 +81,44 @@ jobs:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
           NPM_TOKEN: ${{ secrets.NPM_TOKEN }}
 ```
+
+### With version script
+
+If you need to add additional logic to the version command, you can do so by using a version script.
+
+If the version script is present, this action will run that script instead of `changeset version`, so please make sure that your script calls `changeset version` at some point. All the changes made by the script will be included in the PR.
+
+```yml
+name: Release
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  release:
+    name: Release
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@master
+        with:
+          fetch-depth: 0
+
+      - name: Setup Node.js 12.x
+        uses: actions/setup-node@master
+        with:
+          node-version: 12.x
+
+      - name: Install Dependencies
+        run: yarn
+
+      - name: Create Release Pull Request
+        uses: changesets/action@master
+        with:
+          # this expects you to have a npm script called version that runs some logic and then calls `changeset version`.
+          version: yarn version
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+```

index.ts

@@ -59,6 +59,7 @@ import readChangesets from "@changesets/read";
   let hasChangesets = changesets.length !== 0;
 
   let publishScript = core.getInput("publish");
+  let versionScript = core.getInput("version");
 
   if (!hasChangesets && !publishScript) {
     console.log("No changesets found");
@@ -164,6 +165,11 @@ import readChangesets from "@changesets/read";
     }
 
     await exec("git", ["reset", "--hard", github.context.sha]);
+   
+    if (versionScript) {
+      let [versionCommand, ...versionArgs] = versionScript.split(/\s+/);
+      await exec(versionCommand, versionArgs);
+    } else {
       let changesetsCliPkgJson = await fs.readJson(
         path.join("node_modules", "@changesets", "cli", "package.json")
       );
@@ -171,6 +177,8 @@ import readChangesets from "@changesets/read";
         ? "bump"
         : "version";
       await exec("node", ["./node_modules/@changesets/cli/bin.js", cmd]);
+    }
+
     let searchQuery = `repo:${repo}+state:open+head:${versionBranch}+base:${branch}`;
     let searchResultPromise = octokit.search.issuesAndPullRequests({
       q: searchQuery