merge: when current branch has 1 or > 2 heads, actually abort.
Currently merge just prints abort-like messages to stderr and then
exits with a misleading status 0 (cleverly disguised as "False").
With this change it raises Abort, just like every other fatal error.
#!/bin/sh
# Just exercize debugindexdot
# Create a short file history including a merge.
hg init t
cd t
echo a > a
hg ci -qAm t1 -d '0 0'
echo a >> a
hg ci -m t2 -d '1 0'
hg up -qC 0
echo b >> a
hg ci -m t3 -d '2 0'
HGMERGE=true hg merge -q
hg ci -m merge -d '3 0'
hg debugindexdot .hg/store/data/a.i