Finding what change broke ARM

When building current git for ARM, I see:

  CC      arch/arm/mm/consistent.o
arch/arm/mm/consistent.c: In function `dma_free_coherent':
arch/arm/mm/consistent.c:357: error: `mem_map' undeclared (first use in this function)
arch/arm/mm/consistent.c:357: error: (Each undeclared identifier is reported only once
arch/arm/mm/consistent.c:357: error: for each function it appears in.)
make[2]: *** [arch/arm/mm/consistent.o] Error 1

How can I find what change elsewhere in the kernel tree caused this
breakage?

With bk, you could ask for a per-file revision history of the likely
candidates, and then find the changeset to view the other related
changes.

With git... ?  We don't have per-file revision history so...

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core