name-rev --stdin is slow

name-rev --stdin has some really high start-up time. The example below is on my git.git branch. Is this unavoidable to make name-rev fast for naming high numbers of revisions -- i.e. is it about amortization? Still, 0.7 seconds seems pretty excessive, and on linux-2.6 it even takes 6 seconds.

Anyone care to look into it?

$ time echo HEAD | git name-rev --stdin HEAD

real 0m0.748s user 0m0.588s sys 0m0.080s $ time git name-rev HEAD HEAD master

real 0m0.041s user 0m0.016s sys 0m0.028s