git commit --amend fails

[gegles]

When trying to amend a commit, I see the following error:

Traceback (most recent call last):
  File "/Users/gegles/Workspaces/fasp.io/cmake/git-cmake-format/git-cmake-format.py", line 114, in <module>
    if not isFormattable(FileName):
  File "/Users/gegles/Workspaces/fasp.io/cmake/git-cmake-format/git-cmake-format.py", line 43, in isFormattable
    if '' != Dir and '' != os.path.commonprefix([os.path.relpath(File), os.path.relpath(Dir)]):
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/posixpath.py", line 428, in relpath
    raise ValueError("no path specified")
ValueError: no path specified

Probably need to support the script running with no actual files changed..

[kbenzie]

I tried reproducing this in a simple test repo with the following steps on macOS
but was unsuccessful:

• git init
• Create CMakeLists.txt

  cmake_minimum_required(VERSION 3.4.3 FATAL_ERROR)
  project(check)
  add_subdirectory(git-cmake-format)
  add_executable(check check.cpp)

• Create check.cpp

  int main() { return 0; }

• git commit -m 'Add check executable'
• git commit --amend <- worked as expected

Since this does not reproduce the circumstances which caused your error, is
there anything you can see which I have missed in order to be able to reproduce
your failure?