Add readme + license 0BSD

Author: EliahKagan

LICENSE

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+Permission to use, copy, modify, and/or distribute this software for any
+purpose with or without fee is hereby granted.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+PERFORMANCE OF THIS SOFTWARE.

README.md

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+# pytest-cov-test - Simplified demonstration of GitPython#2052
+
+This is a simplified demonstration of the mechanism underlying the bug fixed in
+[gitpython-developers/GitPython#2052](https://github.com/gitpython-developers/GitPython/pull/2052)
+where a test that runs a subprocess, making an assertion about what the
+subprocess writes to stderr, can fail due to `CoverageWarning` messages
+produced in the subprocess by `pytest-cov`.
+
+## The failure
+
+As there, it is specifically on Cygwin that this currently fails, since the
+warning is not typically generated otherwise. The failure looks like:
+
+```text
+>       assert proc.stderr == f"{sys.executable=}\n"
+E       assert "/home/ek/rep...bin/python'\n" == "sys.executab...bin/python'\n"
+E
+E         + /home/ek/repos-cygwin/pytest-cov-test/.venv/lib/python3.9/site-packages/coverage/core.py:96: CoverageWarning: Couldn't import C tracer: No module named 'coverage.tracer' (no-ctracer)
+E         +   warn(f"Couldn't import C tracer: {IMPORT_ERROR}", slug="no-ctracer", once=True)
+E           sys.executable='/home/ek/repos-cygwin/pytest-cov-test/.venv/bin/python'
+
+test_indirect.py:14: AssertionError
+```
+
+## License
+
+[0BSD](LICENSE)