diff --git a/lib/git/base.rb b/lib/git/base.rb
index 93dcf16e..1b826ccb 100644
--- a/lib/git/base.rb
+++ b/lib/git/base.rb
@@ -69,10 +69,28 @@ def self.root_of_worktree(working_dir)
       status = nil
 
       git_cmd = "#{Git::Base.config.binary_path} -c core.quotePath=true -c color.ui=false rev-parse --show-toplevel 2>&1"
-      result, status = Open3.capture2(git_cmd, chdir: File.expand_path(working_dir))
-      result = result.chomp
+
+      # Option 1 using IO.popen
+      #
+      # IO.popen(git_cmd, chdir: working_dir) do |io|
+      #   status = Process.wait2(io.pid).last
+      #   result = io.read.chomp
+      # end
+
+      # Option 2 using Open3.popen2
+      #
+      # Open3.popen2(git_cmd, chdir: working_dir) do |stdin, stdout, wait_thr|
+      #   status = wait_thr.value
+      #   result = stdout.read.chomp
+      # end
+
+      # Option 3 using Open3.capture3
+      #
+      stdout_s, stderr_s, status = Open3.capture3(git_cmd, chdir: working_dir)
+      result = stdout_s.chomp
 
       raise ArgumentError, "'#{working_dir}' is not in a git working tree" unless status.success?
+
       result
     end
 
diff --git a/lib/git/lib.rb b/lib/git/lib.rb
index 86c34a85..453776c6 100644
--- a/lib/git/lib.rb
+++ b/lib/git/lib.rb
@@ -3,12 +3,11 @@
 require 'tempfile'
 require 'zlib'
 require 'open3'
+require 'stringio'
 
 module Git
   class Lib
 
-    @@semaphore = Mutex.new
-
     # The path to the Git working copy.  The default is '"./.git"'.
     #
     # @return [Pathname] the path to the Git working copy.
@@ -442,10 +441,7 @@ def worktree_prune
     def list_files(ref_dir)
       dir = File.join(@git_dir, 'refs', ref_dir)
       files = []
-      begin
-        files = Dir.glob('**/*', base: dir).select { |f| File.file?(File.join(dir, f)) }
-      rescue
-      end
+      files = Dir.glob(File.join(dir, '**/*')).select { |f| File.file?(f) } rescue nil
       files
     end
 
@@ -1146,41 +1142,14 @@ def command_lines(cmd, *opts, chdir: nil)
       op.split("\n")
     end
 
-    # Takes the current git's system ENV variables and store them.
-    def store_git_system_env_variables
-      @git_system_env_variables = {}
-      ENV_VARIABLE_NAMES.each do |env_variable_name|
-        @git_system_env_variables[env_variable_name] = ENV[env_variable_name]
-      end
-    end
-
-    # Takes the previously stored git's ENV variables and set them again on ENV.
-    def restore_git_system_env_variables
-      ENV_VARIABLE_NAMES.each do |env_variable_name|
-        ENV[env_variable_name] = @git_system_env_variables[env_variable_name]
-      end
-    end
-
-    # Sets git's ENV variables to the custom values for the current instance.
-    def set_custom_git_env_variables
-      ENV['GIT_DIR'] = @git_dir
-      ENV['GIT_WORK_TREE'] = @git_work_dir
-      ENV['GIT_INDEX_FILE'] = @git_index_file
-      ENV['GIT_SSH'] = Git::Base.config.git_ssh
-    end
-
-    # Runs a block inside an environment with customized ENV variables.
-    # It restores the ENV after execution.
-    #
-    # @param [Proc] block block to be executed within the customized environment
-    def with_custom_env_variables(&block)
-      @@semaphore.synchronize do
-        store_git_system_env_variables()
-        set_custom_git_env_variables()
-        return block.call()
-      end
-    ensure
-      restore_git_system_env_variables()
+    # git's ENV variables for the current instance.
+    def custom_git_env_variables
+      {
+        'GIT_DIR' => @git_dir,
+        'GIT_WORK_TREE' => @git_work_dir,
+        'GIT_INDEX_FILE' => @git_index_file,
+        'GIT_SSH' => Git::Base.config.git_ssh,
+      }
     end
 
     def command(*cmd, redirect: '', chomp: true, chdir: nil, &block)
@@ -1200,18 +1169,7 @@ def command(*cmd, redirect: '', chomp: true, chdir: nil, &block)
 
       git_cmd = "#{Git::Base.config.binary_path} #{global_opts} #{escaped_cmd} #{redirect} 2>&1"
 
-      output = nil
-
-      command_thread = nil;
-
-      status = nil
-
-      with_custom_env_variables do
-        command_thread = Thread.new do
-          output, status = run_command(git_cmd, chdir, &block)
-        end
-        command_thread.join
-      end
+      output, status = run_command(git_cmd, chdir, &block)
 
       @logger.info(git_cmd)
       @logger.debug(output)
@@ -1298,9 +1256,20 @@ def run_command(git_cmd, chdir=nil, &block)
       opts = {}
       opts[:chdir] = File.expand_path(chdir) if chdir
 
-      Open3.popen2(git_cmd, opts) do |stdin, stdout, wait_thr|
-        [block.call(stdout), wait_thr.value]
-      end
+      # Option 1 using IO.popen
+      #
+      # [IO.popen(custom_git_env_variables, git_cmd, opts, &block), $?]
+
+      # Option 2 using Open3.popen2
+      #
+      # Open3.popen2(custom_git_env_variables, git_cmd, opts) do |stdin, stdout, wait_thr|
+      #   [block.call(stdout), wait_thr.value]
+      # end
+
+      # Option 3 using Open3.capture3
+      #
+      stdout_s, stderr_s, status = Open3.capture3(custom_git_env_variables, git_cmd, opts)
+      [block.call(StringIO.new(stdout_s)), status]
     end
 
     def escape(s)