[bash] Fix CTRL-R to preserve the latest yank

Close #1216

1. Append a single space so that step 3 won't fail
2. CTRL-E to move to the end of the line
3. CTRL-U to delete the whole line before the cursor
4. CTRL-Y to paste the deleted line
5. ESC+Y to rotate the kill ring and bring back the previous yank before step 3
6. CTRL-U to delete the whole line again
7. Paste `__fzf_history__`
8. ESC+CTRL-E to expand the command substitution
9. ESC+R to redraw the line
10. ESC+^ to expand the history entry (!NUMBER)

shell/key-bindings.bash

@@ -80,7 +80,7 @@ if [[ ! -o vi ]]; then
   fi
 
   # CTRL-R - Paste the selected command from history into the command line
-  bind '"\C-r": " \C-e\C-u`__fzf_history__`\e\C-e\er\e^"'
+  bind '"\C-r": " \C-e\C-u\C-y\ey\C-u`__fzf_history__`\e\C-e\er\e^"'
 
   # ALT-C - cd into the selected directory
   bind '"\ec": " \C-e\C-u`__fzf_cd__`\e\C-e\er\C-m"'