tests/test-extdiff

ssh: make the error message more clear, add a testcase

#!/bin/sh

echo "[extensions]" >> $HGRCPATH
echo "extdiff=" >> $HGRCPATH

hg init a
cd a
echo a > a
hg add
diff -N /dev/null /dev/null 2> /dev/null
if [ $? -ne 0 ]; then
	opt="-p gdiff"
fi
hg extdiff -o -Nr $opt

echo "[extdiff]" >> $HGRCPATH
echo "cmd.falabala=echo" >> $HGRCPATH
echo "opts.falabala=diffing" >> $HGRCPATH

hg falabala

hg help falabala

hg ci -d '0 0' -mtest1

echo b >> a
hg ci -d '1 0' -mtest2

hg falabala -r 0:1 || echo "diff-like tools yield a non-zero exit code"