Add support for partial checkout filters (#1396)

* added filter option & tests

* added build file

* fix test oversight

* added exit 1

* updated docs to specify override

* undo unneeded readme change

* set to undefined rather than empty string

* run git config in correct di

---------

Co-authored-by: Cory Miller <13227161+cory-miller@users.noreply.github.com>

__test__/git-auth-helper.test.ts

@@ -802,6 +802,7 @@ async function setup(testName: string): Promise<void> {
     authToken: 'some auth token',
     clean: true,
     commit: '',
+    filter: undefined,
     sparseCheckout: [],
     sparseCheckoutConeMode: true,
     fetchDepth: 1,