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>

action.yml

@@ -53,10 +53,15 @@ inputs:
   clean:
     description: 'Whether to execute `git clean -ffdx && git reset --hard HEAD` before fetching'
     default: true
+  filter:
+    description: >
+      Partially clone against a given filter.
+      Overrides sparse-checkout if set.
+    default: null
   sparse-checkout:
     description: >
       Do a sparse checkout on given patterns.
-      Each pattern should be separated with new lines
+      Each pattern should be separated with new lines.
     default: null
   sparse-checkout-cone-mode:
     description: >