split up 'if' statements that assign and test (3)

split up 'if' statements that assign and test (3)

Split 'if' statements that combine an assignment with a test.
e.g. from:

    if ((rc = mutt_socket_readln(buf, bufsize, conn)) < 0)

To:

    rc = mutt_socket_readln(buf, bufsize, conn);
    if (rc < 0)

This makes the statements a little easier to read and debug.