esp-idf: Fail to install on mac OS (IDFGH-1808)

Using latest master(a7e8d87d3e5ccc9e5ffcd701a1bac587ba4f43ea), install.sh fails with:

$ ./install.sh
Installing ESP-IDF tools
Installing tools: xtensa-esp32-elf, esp32ulp-elf, openocd-esp32
Skipping xtensa-esp32-elf@esp32-2019r1-8.2.0 (already installed)
Skipping esp32ulp-elf@2.28.51.20170517 (already installed)
Skipping openocd-esp32@v0.10.0-esp32-20190708 (already installed)
Installing Python environment and packages
fatal: The empty string is not a valid path
Traceback (most recent call last):
  File "/Users/cyril/esp/esp-idf/tools/idf_tools.py", line 1317, in <module>
    main(sys.argv[1:])
  File "/Users/cyril/esp/esp-idf/tools/idf_tools.py", line 1313, in main
    action_func(args)
  File "/Users/cyril/esp/esp-idf/tools/idf_tools.py", line 1112, in action_install_python_env
    idf_python_env_path, _, virtualenv_python = get_python_env_path()
  File "/Users/cyril/esp/esp-idf/tools/idf_tools.py", line 813, in get_python_env_path
    idf_version_str = subprocess.check_output(['git', '--work-tree=', global_idf_path, 'describe', '--tags'], cwd=global_idf_path, env=os.environ).decode()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 223, in check_output
    raise CalledProcessError(retcode, cmd, output=output)
subprocess.CalledProcessError: Command '['git', '--work-tree=', '/Users/cyril/esp/esp-idf', 'describe', '--tags']' returned non-zero exit status 128

Please notice that -C is not a valid command for git (you need the generic --work-tree=). I’ve replaced ${IDF_PATH}/tools/idf_tools.py with this:

diff --git a/tools/idf_tools.py b/tools/idf_tools.py
index 3d23412..ef292cf 100755
--- a/tools/idf_tools.py
+++ b/tools/idf_tools.py
@@ -810,7 +810,7 @@ def get_python_env_path():
         with open(version_file_path, "r") as version_file:
             idf_version_str = version_file.read()
     else:
-        idf_version_str = subprocess.check_output(['git', '-C', global_idf_path, 'describe', '--tags'], cwd=global_idf_path, env=os.environ).decode()
+        idf_version_str = subprocess.check_output(['git', '--work-tree=' + global_idf_path, 'describe', '--tags'], cwd=global_idf_path, env=os.environ).decode()
     match = re.match(r'^v([0-9]+\.[0-9]+).*', idf_version_str)
     idf_version = match.group(1)

And it passed.