[merge] Ignore write errors when creating hashcache

[John Arbash Meinel]

Aaron Bentley wrote:
> Aaron Bentley has voted +1 (conditional).
> Status is now: Conditionally approved
> Comment:
> This looks reasonable to me.  But
> - getattr will raise AttributeError unless you specify a default value.  I think you want getattr(tree, '_hashcache', None)
> 
> - I think you should do assertTrue(isinstance(the_hashcache, hashcache.HashCache)), because otherwise the test will appear to succeed.
> 
> 

You are right that I wanted getattr(,None). But the second part is
actually intentional. I wasn't sure how to test working trees that don't
have a hashcache.

I believe dirstate won't have one, because it is rolled into dirstate
itself.

Also, I don't know how Hg or Git would handle a test like this.

Which is why I wasn't positive that we wanted it as a generic working
tree test. Except it seems like something we *would* want out of all
working trees.

John
=:->