Use GIT_SSH environment to specify alternate ssh binary.

[jc: I ended up rewriting Martin's patch due to whitespace
breakage, but the credit goes to Martin for doing the initial
patch to identify what needs to be changed.]
Signed-off-by: NMartin Sivak <mars@nomi.cz>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

connect.c

@@ -382,8 +382,15 @@ int git_connect(int fd[2], char *url, const char *prog)
 		close(pipefd[0][1]);
 		close(pipefd[1][0]);
 		close(pipefd[1][1]);
-		if (protocol == PROTO_SSH)
-			execlp("ssh", "ssh", host, command, NULL);
+		if (protocol == PROTO_SSH) {
+			const char *ssh = getenv("GIT_SSH") ? : "ssh";
+			const char *ssh_basename = strrchr(ssh, '/');
+			if (!ssh_basename)
+				ssh_basename = ssh;
+			else
+				ssh_basename++;
+			execlp(ssh, ssh_basename, host, command, NULL);
+		}
 		else
 			execlp("sh", "sh", "-c", command, NULL);
 		die("exec failed");

rsh.c

@@ -56,10 +56,16 @@ int setup_connection(int *fd_in, int *fd_out, const char *remote_prog,
 		return error("Couldn't create socket");
 	}
 	if (!fork()) {
+		const char *ssh = getenv("GIT_SSH") ? : "ssh";
+		const char *ssh_basename = strrchr(ssh, '/');
+		if (!ssh_basename)
+			ssh_basename = ssh;
+		else
+			ssh_basename++;
 		close(sv[1]);
 		dup2(sv[0], 0);
 		dup2(sv[0], 1);
-		execlp("ssh", "ssh", host, command, NULL);
+		execlp(ssh, ssh_basename, host, command, NULL);
 	}
 	close(sv[0]);
 	*fd_in = sv[1];