Why I fail to use git apply with -3 option :
$ git apply --3way /tmp/0001-my-patch.patch
error: patch failed: a.h:9
Falling back to three-way merge...
Applied patch to 'a.h' cleanly.
error: patch failed: b.c:6
Falling back to three-way merge...
Applied patch to 'b.c' cleanly.
error: patch failed: drivers/Kconfig:1882
Falling back to three-way merge...
Applied patch to 'drivers/Kconfig' with conflicts.
U drivers/Kconfig