Fixed OSError "No such file or directory: None" and make IOError consistent.
The None error occurs when the current working directory is no longer
available, e.g. because it was removed in another shell.
#!/bin/sh
hg init
echo a > a
hg commit -A -ma
echo a >> a
hg commit -mb
echo a >> a
hg commit -mc
hg up 1
echo a >> a
hg commit -md
hg up 1
echo a >> a
hg commit -me
hg up 1
echo % should fail because not at a head
hg merge
hg up
echo % should fail because \> 2 heads
hg merge
echo % should succeed
hg merge 2
hg commit -mm1
echo % should succeed - 2 heads
hg merge
hg commit -mm2
echo % should fail because 1 head
hg merge
true