ci(macos): automatically determine default branch for homebrew formula (#2317)

.github/workflows/CI.yml

@@ -562,10 +562,12 @@ jobs:
             echo "This is a PUSH event"
             clone_url=${{ github.event.repository.clone_url }}
             branch="${{ github.ref_name }}"
+            default_branch="${{ github.event.repository.default_branch }}"
           else
             echo "This is a PR event"
             clone_url=${{ github.event.pull_request.head.repo.clone_url }}
             branch="${{ github.event.pull_request.head.ref }}"
+            default_branch="${{ github.event.pull_request.head.repo.default_branch }}"
           fi
           echo "Branch: ${branch}"
           echo "Clone URL: ${clone_url}"
@@ -575,6 +577,7 @@ jobs:
           cmake \
             -DGITHUB_BRANCH="${branch}" \
             -DGITHUB_CLONE_URL="${clone_url}" \
+            -DGITHUB_DEFAULT_BRANCH="${default_branch}" \
             -DSUNSHINE_CONFIGURE_HOMEBREW=ON \
             -DSUNSHINE_CONFIGURE_ONLY=ON \
             ..

packaging/macos/sunshine.rb

@@ -7,7 +7,7 @@ class @PROJECT_NAME@ < Formula
     tag: "@GITHUB_BRANCH@"
   version "@PROJECT_VERSION@"
   license all_of: ["GPL-3.0-only"]
-  head "@GITHUB_CLONE_URL@", branch: "nightly"
+  head "@GITHUB_CLONE_URL@", branch: "@GITHUB_DEFAULT_BRANCH@"
 
   depends_on "boost" => :build
   depends_on "cmake" => :build