Be more backward compatible with git-ssh-{push,pull}.

HPA reminded me that these programs knows about the name of the
counterpart on the other end and simply symlinking the old name to
new name locally would not be enough.

Signed-off-by: Junio C Hamano <junkio@cox.net>

ssh-pull.c

@@ -0,0 +1,4 @@
+#define COUNTERPART_ENV_NAME "GIT_SSH_PUSH"
+#define COUNTERPART_PROGRAM_NAME "git-ssh-push"
+#define MY_PROGRAM_NAME "git-ssh-pull"
+#include "ssh-fetch.c"