I think that preferences for display-buffer-alist will depend on each user’s workflow. With my rule it will pop up magit-status in the currently active window, then split to show logs, diffs, etc. I don’t normally use more than two windows per frame, so it’s not too bad if it messes things up, but I haven’t noticed it doing that. If it does do something weird, I just use winner-undo until I get back to where I was. For this you have to have (winner-mode) somewhere in your config or start it manually I guess.

For instance, if you had two windows in a vertical split like A | B with point in A, then run magit-status, A will show magit and B won’t change unless you run something like magit-log. Pressing q in the log window will restore B to what it was showing before.

Changing this behavior is probably possible, but I’m satisfied with this so far.

The *shell: pattern is for use with this package: https://github.com/elizagamedev/shell-command-x.el

If you haven’t tried it, I heartily recommend it. I don’t use a dedicated terminal much anymore; this package and https://github.com/bard/emacs-run-command serve my shell needs these days.

(add-to-list 'display-buffer-alist
             '("\\*sly-mrepl"
               (display-buffer-at-bottom)
               (window-height . 12)))
(add-to-list 'display-buffer-alist
             '("\\*Calendar*"
               (display-buffer-at-bottom)))
(add-to-list 'display-buffer-alist
             '("\\*shell:"
               (display-buffer-below-selected)
               (window-height . 12)))
(add-to-list 'display-buffer-alist
             '("\\magit:"
               (display-buffer-same-window)))
(add-to-list 'display-buffer-alist
             '("\\*Man"
               (display-buffer-same-window)))
(add-to-list 'display-buffer-alist
             '("\\*Help"
               (display-buffer-same-window)))
(add-to-list 'display-buffer-alist
             '("\\*helpful"
               (display-buffer-same-window)))