I looked into post-receive hook of an arbitrary git/git-annex repo to find

(git-annex)hopa:/tmp/testds/.git/hooks[master]
$> cat post-receive           
#!/bin/sh
# automatically configured by git-annex
if git annex post-receive --help >/dev/null 2>&1; then git annex post-receive; fi

and wondered why it actually needs conditioning? --help runs for me longer (40-50ms) than actual git annex post-receive call (20ms) when there is nothing todo. So I wondered why wasting time on --help?