How do patch determine which file will be patched?

[Liu Tao <debian@0451.com>]

For example, if the patch file "patch1" is like

diff -u --recursive --new-file aaa/bbb/main.c bbb/main.c
--- aaa/bbb/main.c	Tue Oct 16 17:13:04 2001
+++ bbb/main.c	Tue Oct 16 17:55:57 2001
...

and "patch2":
diff -u --recursive --new-file bbb/main.c aaa/bbb/main.c
--- bbb/main.c	Tue Oct 16 17:13:04 2001
+++ aaa/bbb/main.c	Tue Oct 16 17:55:57 2001
...

both "patch -p0 < patch1" and "patch -p0 < patch2" patches bbb/main.c ?