tests/test-merge-force

run-tests: detect when hghave fails to check for a feature and fail test

hghave exitcode != 0 might mean that hghave failed to check for feature
avaibility. Detect those cases, and fail the test, instead of skipping it.

#!/bin/sh

hg init repo
cd repo

echo a > a
hg ci -qAm 'add a'

echo b > b
hg ci -qAm 'add b'

hg up -qC 0
hg rm a
hg ci -m 'rm a'

hg up -qC 1
rm a

echo '% local deleted a file, remote removed'
hg merge # should fail, since there are deleted files
hg -v merge --force
echo % should show a as removed
hg st

hg ci -m merge
echo % manifest. should not have a:
hg manifest