Fix hg push and hg push -r sometimes creating new heads without --force. Fixing issue179. The algorithm checks if there not more new heads on the remote side than heads which become non-heads due to getting children. Pushing this repo: m /\ 3 3a| |/ / 2 2a |/ 1 to a repo only having 1, 2 and 3 didn't abort requiring --force before. Added test cases for this and some doc strings for used methods.

#!/bin/sh

hg init
echo 123 > a
hg add a
hg commit -m "first" -d "1000000 0" a
mkdir sub
echo 321 > sub/b
hg add sub/b
hg commit -m "second" -d "1000000 0" sub/b
cat sub/b
hg co 0
cat sub/b 2>/dev/null || echo "sub/b not present"
ls sub 2>/dev/null || echo "sub not present"

true