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Repo.index.reset fails on windows #1630

Description

@suvayu

How to reproduce

  1. clone any repo
  2. edit a tracked file
  3. in python, try to reset with
    Repo().index.reset(working_tree=True)
    You will get a stack trace.

Step by step recipe:

$ git clone https://github.com/gitpython-developers/GitPython git-python
$ cd git-python
$ python -m venv --prompt git venv
$ .\venv\Scirpts\Activate.ps1  # or whatever script is appropriate for you
$ rm pyproject.toml  # make any edit
$ git status -sb
## main...origin/main
 D pyproject.toml
$ python
>>> from git import Repo
>>> repo.index.reset(working_tree=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\<user>\code\git-python\git\index\util.py", line 103, in check_default_index
    return func(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\<user>\code\git-python\git\index\base.py", line 1320, in reset
    new_inst = type(self).from_tree(self.repo, commit)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\<user>\code\git-python\git\index\base.py", line 367, in from_tree
    repo.git.read_tree(*arg_list, **kwargs)
  File "C:\Users\<user>\code\git-python\git\cmd.py", line 739, in <lambda>
    return lambda *args, **kwargs: self._call_process(name, *args, **kwargs)
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\user>\code\git-python\git\cmd.py", line 1312, in _call_process
    return self.execute(call, **exec_kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\<user>\code\git-python\git\cmd.py", line 1107, in execute
    raise GitCommandError(redacted_command, status, stderr_value, stdout_value)
git.exc.GitCommandError: Cmd('git') failed due to: exit code(128)
  cmdline: git read-tree --index-output=C:\Users\<user>\code\git-python\.git\tmpxnmxtmmu HEAD
  stderr: 'fatal: unable to write new index file'

Expectation

I was expecting the result would be the equivalent of git reset --hard HEAD. Am I doing something incorrectly here? I'm unfamiliar with Windows, so it's quite possible.

Activity

Byron commented on Aug 19, 2023

@Byron
Member

Maybe git itself is reading the index and GitPython fails to overwrite it shortly after. It's a known Windows filesystem issue.
As a workaround, one should be able to use repo.git.reset(…) to invoke git directly, possibly after changing the index using GitPython.

suvayu commented on Aug 20, 2023

@suvayu
Author

Thanks for the confirmation. For now I have worked around it with Repo.head.reset(working_tree=True) When I get some time, I'll experiment a bit and try to understand this better.

EliahKagan commented on Dec 1, 2023

@EliahKagan
Member

This happens because IndexFile.from_tree (used by IndexFile.reset) uses NamedTemporaryFile in a way that works on Unix-like systems but on Windows prevents git read-tree from overwriting the file by moving its own temporary file to its location. I've proposed a fix in #1751.

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