  We obtain an almost complete understanding of the mean-field phase diagram of
the two-dimensional Hubbard model on a square lattice with a sizable
next-nearest neighbor hopping and a moderate interaction strength. In
particular, we clarify the nature of the transition region between the spiral
and the stripe phase. Complementing previous [Phys. Rev. B 108, 035139 (2023)]
real-space Hartree-Fock calculations on large finite lattices, we solve the
mean-field equations for coplanar unidirectional magnetic order directly in the
thermodynamic limit, and we determine the nature of the magnetic states right
below the mean-field critical temperature $T^*$ by a Landau free energy
analysis. While the magnetic order for filling factors $n \geq 1$ is always of
N\'eel type, for $n \leq 1$ the following sequence of magnetic states is found
as a function of increasing hole-doping: N\'eel, planar circular spiral,
multi-spiral, and collinear spin-charge stripe states. Multi-spiral states are
superpositions of several spirals with distinct wave vectors, and lead to
concomitant charge order. We finally point out that nematic and charge orders
inherited from the magnetic order can survive even in the presence of
fluctuations, and we present a corresponding qualitative phase diagram.
