git/workflows: Checkout code from fork for pr checks.

Signed-off-by: Andrew Clemons <andrew.clemons@gmail.com>

Signed-off-by: Willy Sudiarto Raharjo <willysr@slackbuilds.org>

.github/workflows/ci.yml

@@ -29,11 +29,13 @@ jobs:
         with:
           fetch-depth: 2
           ref: ${{ github.head_ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
 
       - name: Get slackbuild directories which have changes.
         id: changed-dirs
         uses: tj-actions/changed-files@c860b5c47fa71f461da850094ef2f6e3d6514e44 # v38.1.3
         with:
+          base_sha: ${{ github.event.pull_request.base.sha }}
           dir_names: true
           dir_names_exclude_current_dir: true
           dir_names_max_depth: 2
@@ -71,6 +73,7 @@ jobs:
       - uses: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744 # v3.6.0
         with:
           ref: ${{ github.head_ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
 
       - name: Run sbolint
         run: |