ssh-push.con commit xdiff: generate "anti-diffs" aka what is common to two files (a9ed376)
   1#define COUNTERPART_ENV_NAME "GIT_SSH_PULL"
   2#define COUNTERPART_PROGRAM_NAME "git-ssh-pull"
   3#define MY_PROGRAM_NAME "git-ssh-push"
   4#include "ssh-upload.c"