git blame crashes with internal error

Hi Junio,

git blame just decided to crash on me, when I tried to use it while resolving a merge conflict. Interesting is probably, that it crashes when given the filename of a file that is not _directly_ affected by the merge, but contains code that originates from a file that caused conlicts.

Error message is: fatal: internal error: ce_mode is 0

I tried all git releases from 1.5.3 to 1.5.3.4 as well as the current master and all of them crashed. A small shell script to reproduce the problem is attached.

Thanks, Björn