diff --git a/Library/Homebrew/test/utils/git_spec.rb b/Library/Homebrew/test/utils/git_spec.rb
new file mode 100644
index 0000000000..e511212f49
--- /dev/null
+++ b/Library/Homebrew/test/utils/git_spec.rb
@@ -0,0 +1,150 @@
+require "utils/git"
+
+describe Git do
+  before(:each) do
+    git = HOMEBREW_SHIMS_PATH/"scm/git"
+
+    HOMEBREW_CACHE.cd do
+      system git, "init"
+
+      File.open(file, "w") { |f| f.write("blah") }
+      system git, "add", HOMEBREW_CACHE/file
+      system git, "commit", "-m", "'File added'"
+      @h1 = `git rev-parse HEAD`
+
+      File.open(file, "w") { |f| f.write("brew") }
+      system git, "add", HOMEBREW_CACHE/file
+      system git, "commit", "-m", "'written to File'"
+      @h2 = `git rev-parse HEAD`
+    end
+  end
+
+  let(:file) { "blah.rb" }
+  let(:hash1) { @h1[0..6] }
+  let(:hash2) { @h2[0..6] }
+
+  describe "#last_revision_commit_of_file" do
+    it "gives last revision commit when before_commit is nil" do
+      expect(
+        described_class.last_revision_commit_of_file(HOMEBREW_CACHE, file),
+      ).to eq(hash1)
+    end
+
+    it "gives revision commit based on before_commit when it is not nil" do
+      expect(
+        described_class.last_revision_commit_of_file(HOMEBREW_CACHE,
+                                                    file,
+                                                    before_commit: hash2),
+      ).to eq(hash2)
+    end
+  end
+
+  describe "#last_revision_of_file" do
+    it "returns last revision of file" do
+      expect(
+        described_class.last_revision_of_file(HOMEBREW_CACHE,
+                                              HOMEBREW_CACHE/file),
+      ).to eq("blah")
+    end
+
+    it "returns last revision of file based on before_commit" do
+      expect(
+        described_class.last_revision_of_file(HOMEBREW_CACHE, HOMEBREW_CACHE/file,
+                                              before_commit: "0..3"),
+      ).to eq("brew")
+    end
+  end
+end
+
+describe Utils do
+  before(:each) do
+    described_class.clear_git_available_cache
+  end
+
+  describe "::git_available?" do
+    it "returns true if git --version command succeeds" do
+      expect(described_class.git_available?).to be_truthy
+    end
+
+    it "returns false if git --version command does not succeed" do
+      stub_const("HOMEBREW_SHIMS_PATH", HOMEBREW_PREFIX/"bin/shim")
+      expect(described_class.git_available?).to be_falsey
+    end
+  end
+
+  describe "::git_path" do
+    it "returns nil when git is not available" do
+      stub_const("HOMEBREW_SHIMS_PATH", HOMEBREW_PREFIX/"bin/shim")
+      expect(described_class.git_path).to eq(nil)
+    end
+
+    it "returns path of git when git is available" do
+      expect(described_class.git_path).to end_with("git")
+    end
+  end
+
+  describe "::git_version" do
+    it "returns nil when git is not available" do
+      stub_const("HOMEBREW_SHIMS_PATH", HOMEBREW_PREFIX/"bin/shim")
+      expect(described_class.git_path).to eq(nil)
+    end
+
+    it "returns version of git when git is available" do
+      expect(described_class.git_version).not_to be_nil
+    end
+  end
+
+  describe "::ensure_git_installed!" do
+    it "returns nil if git already available" do
+      expect(described_class.ensure_git_installed!).to be_nil
+    end
+
+    context "when git is not already available" do
+      before do
+        stub_const("HOMEBREW_SHIMS_PATH", HOMEBREW_PREFIX/"bin/shim")
+      end
+
+      it "can't install brewed git if homebrew/core is unavailable" do
+        allow_any_instance_of(Pathname).to receive(:directory?).and_return(false)
+        expect { described_class.ensure_git_installed! }.to raise_error("Git is unavailable")
+      end
+
+      it "raises error if can't install git" do
+        stub_const("HOMEBREW_BREW_FILE", HOMEBREW_PREFIX/"bin/brew")
+        expect { described_class.ensure_git_installed! }.to raise_error("Git is unavailable")
+      end
+
+      it "installs git" do
+        allow(Homebrew).to receive(:_system).with(any_args).and_return(true)
+        described_class.ensure_git_installed!
+      end
+    end
+  end
+
+  describe "::git_remote_exists" do
+    it "returns true when git is not available" do
+      stub_const("HOMEBREW_SHIMS_PATH", HOMEBREW_PREFIX/"bin/shim")
+      expect(described_class.git_remote_exists("blah")).to be_truthy
+    end
+
+    context "when git is available" do
+      it "returns true when git remote exists", :needs_network do
+        git = HOMEBREW_SHIMS_PATH/"scm/git"
+        url = "http://github.com/Homebrew/homebrew.github.io"
+        repo = HOMEBREW_CACHE/"hey"
+        repo.mkpath
+
+        repo.cd do
+          system git, "init"
+          system git, "remote", "add", "origin", url
+        end
+
+        expect(described_class.git_remote_exists(url)).to be_truthy
+      end
+
+      it "returns false when git remote does not exist" do
+        expect(described_class.git_remote_exists("blah")).to be_falsey
+      end
+    end
+  end
+end
diff --git a/Library/Homebrew/utils/git.rb b/Library/Homebrew/utils/git.rb
index 43d93b64ec..1fc01188cc 100644
--- a/Library/Homebrew/utils/git.rb
+++ b/Library/Homebrew/utils/git.rb
@@ -16,8 +16,7 @@ module Git
   def last_revision_of_file(repo, file, before_commit: nil)
     relative_file = Pathname(file).relative_path_from(repo)
 
-    commit_hash = last_revision_commit_of_file(repo, file, before_commit: before_commit)
-
+    commit_hash = last_revision_commit_of_file(repo, relative_file, before_commit: before_commit)
     out, = Open3.capture3(
       HOMEBREW_SHIMS_PATH/"scm/git", "-C", repo,
       "show", "#{commit_hash}:#{relative_file}"