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

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

__test__/input-helper.test.ts

@@ -79,6 +79,7 @@ describe('input-helper tests', () => {
     expect(settings.clean).toBe(true)
     expect(settings.commit).toBeTruthy()
     expect(settings.commit).toBe('1234567890123456789012345678901234567890')
+    expect(settings.filter).toBe(undefined)
     expect(settings.sparseCheckout).toBe(undefined)
     expect(settings.sparseCheckoutConeMode).toBe(true)
     expect(settings.fetchDepth).toBe(1)