Respect HEX_REPO_IDENTIFIER environment variable

The new variable allows users to opt-out of identification by setting
the value to anything other than `1` or `true`. It remains enabled by
default.

Author: sorentwo

lib/hex/http.ex

@@ -49,7 +49,7 @@ defmodule Hex.HTTP do
     default_headers = %{"user-agent" => user_agent()}
 
     default_headers
-    |> add_client_identifier_header()
+    |> add_repo_identifier_header()
     |> Map.merge(headers)
   end
 
@@ -273,8 +273,8 @@ defmodule Hex.HTTP do
     host
   end
 
-  defp add_client_identifier_header(headers) do
-    case Hex.Utils.client_identifier() do
+  defp add_repo_identifier_header(headers) do
+    case Hex.Utils.repo_identifier() do
       nil -> headers
       identifier -> Map.put(headers, "x-hex-repo-id", identifier)
     end

lib/hex/utils.ex

@@ -333,8 +333,9 @@ defmodule Hex.Utils do
 
   Returns `nil` if git is not available or the directory is not a git repository.
   """
-  def client_identifier do
-    with path when is_binary(path) <- System.find_executable("git"),
+  def repo_identifier do
+    with flag when flag in ["1", "true"] <- System.get_env("HEX_REPO_IDENTIFIER", "1"),
+         path when is_binary(path) <- System.find_executable("git"),
          {output, 0} <- System.cmd("git", ["rev-list", "--max-parents=0", "HEAD"]) do
       output
       |> String.trim()

test/hex/utils_test.exs

@@ -1,9 +1,9 @@
 defmodule Hex.UtilsTest do
   use ExUnit.Case
 
-  describe "client_identifier/0" do
+  describe "repo_identifier/0" do
     test "an identifier is included within a repository" do
-      assert Hex.Utils.client_identifier() =~ ~r/^[a-f0-9]{64}$/
+      assert Hex.Utils.repo_identifier() =~ ~r/^[a-f0-9]{64}$/
     end
 
     test "identifier is nil outside of a repository" do
@@ -18,10 +18,20 @@ defmodule Hex.UtilsTest do
       try do
         File.mkdir!(dir)
 
-        File.cd!(dir, fn -> refute Hex.Utils.client_identifier() end)
+        File.cd!(dir, fn -> refute Hex.Utils.repo_identifier() end)
       after
         File.rmdir(dir)
       end
     end
+
+    test "identifier is nil when disabled by an environment variable" do
+      System.put_env("HEX_REPO_IDENTIFIER", "0")
+      refute Hex.Utils.repo_identifier()
+
+      System.put_env("HEX_REPO_IDENTIFIER", "false")
+      refute Hex.Utils.repo_identifier()
+    after
+      System.delete_env("HEX_REPO_IDENTIFIER")
+    end
   end
 end