Fixed situations in which cwd was specified as a relative path and used with (default) commitMode: git-cli (#486)

* fix: use latest ghcommit and fix cwd for git-cli

- `cwd` was not working correctly when commitMode was set to `git-cli`,
  as it was attempting to resolve the `cwd` twice.
  (This problem only occured when specifying a relative path for `cwd`.)
- Update `ghcommit`, and avoid calling `process.chdir()` to change the
  working directory. Instead, we now pass the `cwd` option everywhere.

fixes #475

* simplify

* Apply suggestions from code review

---------

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

package.json

@@ -33,7 +33,7 @@
     "@actions/core": "^1.11.1",
     "@actions/exec": "^1.1.1",
     "@actions/github": "^6.0.1",
-    "@changesets/ghcommit": "1.4.0",
+    "@changesets/ghcommit": "^2.0.0",
     "@changesets/pre": "^1.0.9",
     "@changesets/read": "^0.5.3",
     "@manypkg/get-packages": "^1.1.3",