alexander@goblin /tmp $ cat src1/1.c
#include <stdio.h>

int main(int argc, char **argv) {
        return 0;
}
alexander@goblin /tmp $ cat src2/1.c
#include <stdio.h>

int main(int argc, char **argv) {
        printf("Hello world!");
        return 0;
}
alexander@goblin /tmp $ diff -rc src{1,2} | tee src1-2.patch
diff -rc src1/1.c src2/1.c
*** src1/1.c    2012-07-07 23:17:56.822846190 +0400
--- src2/1.c    2012-07-07 23:19:35.808852144 +0400
***************
*** 1,5 ****
--- 1,6 ----
  #include <stdio.h>

  int main(int argc, char **argv) {
+       printf("Hello world!");
        return 0;
  }
alexander@goblin /tmp $ cp -r src{1,3}
alexander@goblin /tmp $ cd src3/
alexander@goblin /tmp/src3 $ cat 1.c
#include <stdio.h>

int main(int argc, char **argv) {
        return 0;
}
alexander@goblin /tmp/src3 $ patch -rp1 <../src1-2.patch
patching file 1.c
alexander@goblin /tmp/src3 $ cat 1.c
#include <stdio.h>

int main(int argc, char **argv) {
        printf("Hello world!");
        return 0;
}