With wrapping up 2015, I was curious to run some GitStats this morning on the latest Linux kernel code-base. It reported 20860782 lines (keep in mind that line count includes documentation, tools, Kconfig, and other lines rather than just purely code), 52221 files, and 562219 commits by 14614 authors.
2015 saw 63,460 commits, which is actually down quite a bit from 75,015 commits in 2014, 70,954 commits in 2013, and 65,403 commits in 2012. This year there were 3,427,774 lines added and 1,690,557 removed -- or a net gain of 1,737,217 lines for 2015.
Top authors of the Linux kernel in 2015 besides Linus Torvalds himself included Ben Skeggs, Takashi Iwai, David Miller, Mark Brown, Stephen Boyd, H Hartley Sweeten, Arnd Bergmann, Al Viro, Ingo Molnar, and the other usual suspects. There were 3,690 different authors to the Linux kernel in 2015.
If you are curious about other Linux kernel Git statistics, see the raw data here.