Add new command `prelude-top-join-line`

Saner version of the built-in `join-line`, that joins lines from the top
to the bottom.

README.md

@@ -197,7 +197,7 @@ Keybinding         | Description
 <kbd>C-+</kbd>     | Increase font size(`text-scale-increase`).
 <kbd>C--</kbd>     | Decrease font size(`text-scale-decrease`).
 <kbd>C-x O</kbd>   | Go back to previous window (the inverse of `other-window` (`C-x o`)).
-<kbd>C-x ^</kbd>   | Join two lines into one(`join-line`).
+<kbd>M-^</kbd>     | Join two lines into one(`prelude-top-join-line`).
 <kbd>C-x p</kbd>   | Start `proced` (manage processes from Emacs; works only in Linux).
 <kbd>C-x m</kbd>   | Start `eshell`.
 <kbd>C-x M-m</kbd> | Start your default shell.

core/prelude-core.el

@@ -97,6 +97,11 @@ Position the cursor at its beginning, according to the current mode."
   (move-end-of-line nil)
   (newline-and-indent))
 
+(defun prelude-top-join-line ()
+  "Join the current line with the line beneath it."
+  (interactive)
+  (delete-indentation 1))
+
 (defun prelude-move-line-up ()
   "Move the current line up."
   (interactive)

core/prelude-global-keybindings.el

@@ -45,7 +45,7 @@
                                 (other-window -1))) ;; back one
 
 ;; Indentation help
-(global-set-key (kbd "C-x ^") 'join-line)
+(global-set-key (kbd "M-^") 'prelude-top-join-line)
 
 ;; Start proced in a similar manner to dired
 (global-set-key (kbd "C-x p") 'proced)