Gitpython: BrokenPipeError on KeyboardInterrupt

[mallamanis]

I am using the latest GitPython on pip and I have bumped into a weird behavior, that seems to be buggy. I have replicated the behavior both with Python 2.7 and 3.4 and has emerged after updating to newer versions of GitPython. Consider the following snippet (assumes a git repository on the current directory):

``` [python]
import time
from git import Repo, TagReference

repository = Repo('.')
current_commit = repository.head.commit
tag_object = TagReference.create(repository, 'test', message='msg')

try:
for i in range(10):
time.sleep(1)

except KeyboardInterrupt:
print("Interrupted. Exiting gracefully...")

data = tag_object.tag.message

If you interrupt (Ctrl+C) the loop, then the last statement fails with a broken pipe exception (full stack trace below). If the code is _not_ interrupted everything succeeds. Also removing the `current_commit = repository.head.commit` line, makes the problem go away, even if you interrupt a loop.

I presume that it has to do with the handling of the SIGTERM emitted with a Ctrl+C, but I am not sure if this is true.

The stack trace:

Traceback (most recent call last):
File "./bugreplicate.py", line 15, in
data = tag_object.tag.message
File "/usr/local/lib/python2.7/dist-packages/git/refs/tag.py", line 40, in tag
obj = self.object
File "/usr/local/lib/python2.7/dist-packages/git/refs/symbolic.py", line 176, in _get_object
return Object.new_from_sha(self.repo, hex_to_bin(self.dereference_recursive(self.repo, self.path)))
File "/usr/local/lib/python2.7/dist-packages/git/objects/base.py", line 65, in new_from_sha
oinfo = repo.odb.info(sha1)
File "/usr/local/lib/python2.7/dist-packages/git/db.py", line 40, in info
hexsha, typename, size = self._git.get_object_header(bin_to_hex(sha))
File "/usr/local/lib/python2.7/dist-packages/git/cmd.py", line 984, in get_object_header
return self.__get_object_header(cmd, ref)
File "/usr/local/lib/python2.7/dist-packages/git/cmd.py", line 972, in __get_object_header
cmd.stdin.flush()
IOError: [Errno 32] Broken pipe
```

Some more context: I am using GitPython for experimenter link and need a way to handle KeyboardInterruptions. When a Ctrl+C is pressed, I want to be able to safely store data into the git repository.

[Byron]

Thanks for the report ! I was able to reproduce the issue, and also found a workaround for now. What you can do is to use a different object database implementation when instantiating the repo like so:

repository = Repo('.', odbt=git.GitDB)

The default object database implementation changed between the versions of gitpython, from the one you see above (pure python) to one that uses a long-running git subprocess to stream objects. The latter is faster and generally preferred, but apparently interacts badly with certain signals.

As GitPython is in maintenance mode and has no functional test suite just yet (which I would need to test these interaction to find a fix), I will leave this one open hoping that others with a similar issue find it (and the workaround).

[mallamanis]

I've also found another workaround, where I create a new Repo each time I use it (instead of having a persistent object through the lifetime of my program). Since this is a corner case with reasonable workarounds, I'd be happy to consider this issue closed/de-prioritized. It's up to you of course :)