GitLab

* mouse.el (mouse-drag-window-above)
(mouse-drag-move-window-bottom, mouse-drag-move-window-top)
(mouse-drag-mode-line-1, mouse-drag-header-line)
(mouse-drag-vertical-line-rightward-window): Remove.
(mouse-drag-line): New function.
(mouse-drag-mode-line, mouse-drag-header-line)
(mouse-drag-vertical-line): Call mouse-drag-line.
* window.el (window-at-side-p, windows-at-side): New functions.