fix(marks): undo reverts a mark set after the change #41330

Problem:
A named mark updated after a change is moved back (treated as the
original mark) by undo:

    :1mark d
    :$
    dw
    :2mark d   " 'd is on line 2
    :undo      " 'd is back on line 1

The undo header snapshots `b_namedm` when the change is recorded, and
`u_undoredo()` restores that snapshot indiscriminately.

Solution:
Update the pending header's snapshot when a mark is set explicitly.
Marks that the change itself moved go through mark_adjust(), not
setmark_pos(), so those are still reverted.

Similar to 2546741d1b36 (for extmarks): an explicit set inside an undo
block is confused with an edit-driven adjustment. But the extmarks case
is dealing with mid-edit moves, whereas named/regular marks only need
the stale snapshot dropped.

0 files changed, 0 insertions, 0 deletions