vim-patch:7.4.758

Problem:    When 'conceallevel' is 1 and quitting the command-line window with
            CTRL-C the first character ':' is erased.
Solution:   Reset 'conceallevel' in the command-line window. (Hirohito
            Higashi)

fa67fbe6b8

src/nvim/ex_getln.c

@@ -5136,6 +5136,8 @@ static int ex_window(void)
 
     /* Don't execute autocommands while deleting the window. */
     block_autocmds();
+    // Avoid command-line window first character being concealed
+    curwin->w_p_cole = 0;
     wp = curwin;
     bp = curbuf;
     win_goto(old_curwin);