problem with git grep -P

Hi, I'm not getting output from git grep -P. Simplified test case:

$ git grep -P '^ ' t/t4012-diff-binary.sh (nothing)

$ git grep -E '^ ' t/t4012-diff-binary.sh t/t4012-diff-binary.sh: a | 2 +- t/t4012-diff-binary.sh: b | Bin t/t4012-diff-binary.sh: c | 2 +- t/t4012-diff-binary.sh: d | Bin t/t4012-diff-binary.sh: 4 files changed, 2 insertions(+), 2 deletions(-) t/t4012-diff-binary.sh: binfile | Bin 0 -> 1026 bytes t/t4012-diff-binary.sh: textfile | 10000 +++++++++++++++++++++++++++++++

I would expect -P to give the same results as -E.

Am I missing something special about pcre?

$ git --version git version 1.7.9.5.g1210a (AFAICT this hasn't changed since grep -P was merged)

I have libpcre3 8.12-4 from debian.

-- Zbyszek