git-fame
https://github.com/oleander/git-fame-rb
This is a nice tool to get the count for all authors at once, including commit and modified files count:
sudo apt-get install ruby-dev
sudo gem install git_fame
cd /path/to/gitdir && git fame
There is also Python version at https://github.com/casperdcl/git-fame (mentioned by @fracz):
sudo apt-get install python-pip python-dev build-essential
pip install --user git-fame
cd /path/to/gitdir && git fame
Sample output:
Total number of files: 2,053
Total number of lines: 63,132
Total number of commits: 4,330
+------------------------+--------+---------+-------+--------------------+
| name | loc | commits | files | percent |
+------------------------+--------+---------+-------+--------------------+
| Johan Sørensen | 22,272 | 1,814 | 414 | 35.3 / 41.9 / 20.2 |
| Marius Mathiesen | 10,387 | 502 | 229 | 16.5 / 11.6 / 11.2 |
| Jesper Josefsson | 9,689 | 519 | 191 | 15.3 / 12.0 / 9.3 |
| Ole Martin Kristiansen | 6,632 | 24 | 60 | 10.5 / 0.6 / 2.9 |
| Linus Oleander | 5,769 | 705 | 277 | 9.1 / 16.3 / 13.5 |
| Fabio Akita | 2,122 | 24 | 60 | 3.4 / 0.6 / 2.9 |
| August Lilleaas | 1,572 | 123 | 63 | 2.5 / 2.8 / 3.1 |
| David A. Cuadrado | 731 | 111 | 35 | 1.2 / 2.6 / 1.7 |
| Jonas Ängeslevä | 705 | 148 | 51 | 1.1 / 3.4 / 2.5 |
| Diego Algorta | 650 | 6 | 5 | 1.0 / 0.1 / 0.2 |
| Arash Rouhani | 629 | 95 | 31 | 1.0 / 2.2 / 1.5 |
| Sofia Larsson | 595 | 70 | 77 | 0.9 / 1.6 / 3.8 |
| Tor Arne Vestbø | 527 | 51 | 97 | 0.8 / 1.2 / 4.7 |
| spontus | 339 | 18 | 42 | 0.5 / 0.4 / 2.0 |
| Pontus | 225 | 49 | 34 | 0.4 / 1.1 / 1.7 |
+------------------------+--------+---------+-------+--------------------+
But be warned: as mentioned by Jared in the comment, doing it on a very large repository will take hours. Not sure if that could be improved though, considering that it must process so much Git data.