rust-cpython: add panicking version of borrow_mut() and use it
The original borrow_mut() is renamed to try_borrow_mut().
Since leak_immutable() no longer incref the borrow count, the caller should
know if the underlying value is borrowed or not. No Python world is involved.
That's why we can simply use the panicking borrow_mut().
#!/usr/bin/env bash
hg init remote
cd remote
echo "0" >> afile
hg add afile
hg commit -m "0.0"
echo "1" >> afile
hg commit -m "0.1"
echo "2" >> afile
hg commit -m "0.2"
echo "3" >> afile
hg commit -m "0.3"
hg update -C 0
echo "1" >> afile
hg commit -m "1.1"
echo "2" >> afile
hg commit -m "1.2"
echo "a line" > fred
echo "3" >> afile
hg add fred
hg commit -m "1.3"
hg mv afile adifferentfile
hg commit -m "1.3m"
hg update -C 3
hg mv afile anotherfile
hg commit -m "0.3m"
hg bundle -a ../remote.hg
cd ..
rm -Rf remote