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 foo > a
hg add a
hg commit -m "1" -d "1000000 0"
hg verify
chmod -r .hg/data/a.d
hg verify 2>/dev/null || echo verify failed
chmod +r .hg/data/a.d
hg verify 2>/dev/null || echo verify failed
chmod -w .hg/data/a.d
echo barber > a
hg commit -m "2" -d "1000000 0" 2>/dev/null || echo commit failed