[mini.diff] Allow setting overlay for non-active buffers

[kalomak]

Currently BufWinEnter calls update_buf_cache which always sets overlay = false, meaning overlay can not be triggered for hidden buffers in practice and gets disabled when switching back from another buffer. Example:

MiniDiff.enable(hidden_buf)
MiniDiff.toggle_overlay(hidden_buf) -- overlay = true
-- Later display hidden_buf in a window
-- BufWinEnter resets overlay = false

Patch to change:
nvim-mini/mini.diff@fb548f0

Maybe this could be added as a config option?

[echasnovski]

Thanks for the suggestion!

At glance, this looks reasonable and the change (similar but a bit more robust than in the linked patch) passes all the tests. I'll take a closer look if maybe there was some hidden undocumented+untested issue.

[echasnovski]

This should now be resolved on the latest main: enabling overlay for the hidden buffer persists even after it is unhidden.