utils/git_repository: use Pathname.pwd if no repo specified

Library/Homebrew/test/utils/git_repository_spec.rb

@@ -20,6 +20,10 @@ describe Utils do
     it "returns the revision at HEAD" do
       expect(described_class.git_head(HOMEBREW_CACHE)).to eq(head_revision)
       expect(described_class.git_head(HOMEBREW_CACHE, length: 5)).to eq(head_revision[0...5])
+      HOMEBREW_CACHE.cd do
+        expect(described_class.git_head).to eq(head_revision)
+        expect(described_class.git_head(length: 5)).to eq(head_revision[0...5])
+      end
     end
   end
 
@@ -27,6 +31,10 @@ describe Utils do
     it "returns the short revision at HEAD" do
       expect(described_class.git_short_head(HOMEBREW_CACHE)).to eq(short_head_revision)
       expect(described_class.git_short_head(HOMEBREW_CACHE, length: 5)).to eq(head_revision[0...5])
+      HOMEBREW_CACHE.cd do
+        expect(described_class.git_short_head).to eq(short_head_revision)
+        expect(described_class.git_short_head(length: 5)).to eq(head_revision[0...5])
+      end
     end
   end
 end

Library/Homebrew/utils/git_repository.rb

@@ -7,7 +7,7 @@ module Utils
   sig do
     params(repo: T.any(String, Pathname), length: T.nilable(Integer), safe: T::Boolean).returns(T.nilable(String))
   end
-  def self.git_head(repo, length: nil, safe: true)
+  def self.git_head(repo = Pathname.pwd, length: nil, safe: true)
     return git_short_head(repo, length: length) if length.present?
 
     repo = Pathname(repo).extend(GitRepositoryExtension)
@@ -17,7 +17,7 @@ module Utils
   sig do
     params(repo: T.any(String, Pathname), length: T.nilable(Integer), safe: T::Boolean).returns(T.nilable(String))
   end
-  def self.git_short_head(repo, length: nil, safe: true)
+  def self.git_short_head(repo = Pathname.pwd, length: nil, safe: true)
     repo = Pathname(repo).extend(GitRepositoryExtension)
     repo.git_short_head(length: length, safe: safe)
   end