tj/git-extra repo:
This PR: ~83% faster:
real    0m2.863s
user    0m1.799s
sys     0m1.596s

Current code:
real    0m6.151s
user    0m10.673s
sys     0m7.714s

git/git repo:
This PR: ~99% faster:
real    0m28.329s
user    0m41.931s
sys     0m13.390s

Current code:
real    21m23.475s
user    73m27.860s
sys     8m2.065s

torvalds/linux repo:
This PR: ~98% faster
real    11m35.754s
user    11m45.818s
sys     4m14.276s

Current code:
real    507m44.527s
user    1025m12.210s
sys     225m39.957s