Make git add work consistently with subdirectories (#473)

* Make git add work consistently with subdirectories

Currently, depending on your `commitMode`,
when running the action with `cwd` set to a subdirectory of a repo,
the action will either:

- `git-cli`: add the files changed in the subdirectory only
- `github-api`: add files changed anywhere in the repository

This commit brings github-api in line with git-cli,
so that it only adds files in the current working directory.

* Explicitly set `cwd` for all exec calls

* Avoid using `ExecOptions` from `@actions/exec`

* Rename type

* remove redundant `filter`

---------

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

src/run.ts

@@ -66,7 +66,7 @@ type PublishOptions = {
   octokit: Octokit;
   createGithubReleases: boolean;
   git: Git;
-  cwd?: string;
+  cwd: string;
 };
 
 type PublishedPackage = { name: string; version: string };
@@ -85,7 +85,7 @@ export async function runPublish({
   git,
   octokit,
   createGithubReleases,
-  cwd = process.cwd(),
+  cwd,
 }: PublishOptions): Promise<PublishResult> {
   let [publishCommand, ...publishArgs] = script.split(/\s+/);