Re: git-diff passes <rev>:<path> args to GIT_EXTERNAL_DIFF incorrectly?

[Dmitry Nikulin <pastafariant@gmail.com>]

On Fri, 30 Aug 2019 at 17:27, Jeff King <peff@peff.net> wrote:

> I think you have an extra "old-filename" in the second list.
Agreed. My misunderstanding was that I had thought that when
documentation said "path", it meant "argv[0], the path to the diff
executable".

> Interesting. I _don't_ see that splitting when I run the same command in
> your demo repo (nor, looking at Git's code, do I see how it could
> happen; we always add the metainfo as a single argument).
Szeder Gábor below has guessed at the cause. I have tested it a little more:

# Test script to ensure that shell does not get in the way
$ cat test.py
import sys
import subprocess

subprocess.check_call([
    'python%s' % sys.argv[1],
    './print_argv.py',
    'similarity index 90%\nrename from file1.txt\nrename to
file1-mv.txt\nindex 2bef330..f8fd673 100644\n',
])

# Python 2, expected behavior
$ python3 test.py 2
['./print_argv.py',
 'similarity index 90%\nrename from file1.txt\nrename to
file1-mv.txt\nindex 2bef330..f8fd673 100644\n']

# Python 3, broken behavior observed before
$ python3 test.py 3
['./print_argv.py',
 'similarity index 90%\n'
 'rename from file1.txt\n'
 'rename to file1-mv.txt\n'
 'index 2bef330..f8fd673 100644\n']

# Directly via shell. Python 2, expected behavior
$ python2 print_argv.py 'similarity index 90%\nrename from
file1.txt\nrename to file1-mv.txt\nindex 2bef330..f8fd673 100644\n'
['print_argv.py',
 'similarity index 90%\\nrename from file1.txt\\nrename to
file1-mv.txt\\nindex 2bef330..f8fd673 100644\\n']

# Python 3, WTF
$ python3 print_argv.py 'similarity index 90%\nrename from
file1.txt\nrename to file1-mv.txt\nindex 2bef330..f8fd673 100644\n'
['print_argv.py',
 'similarity index 90%\\nrename from file1.txt\\nrename to '
 'file1-mv.txt\\nindex 2bef330..f8fd673 100644\\n']