core.pager handling broken

I don't have time to look into it, but something broke the core.pager  
variable.  I've bisected it down to  
"e90fdc39b6903502192b2dd11e5503cea721a1ad: Clean up work-tree  
handling".  With this commit:

$ git config core.pager
tig
$ git log
# Uses less
$ GIT_PAGER=tig git log
# Uses tig

I don't have time to track it down right now (I'm off visiting  
family), but will look into it tomorrow unless someone thinks it's  
obvious and points it out before then.

~~ Brian