turn off powerline characters in ariline, and set vimdiff as difftool

.gitconfig

@@ -12,3 +12,5 @@
         date = format:%Y-%m-%d %H:%M:%S
 [format]
         pretty = format:'%C(yellow)%h %Cred%ad %Cblue%an %Cgreen%d %Creset%s'
+[diff]
+        tool = vimdiff

.vimrc

@@ -37,8 +37,8 @@ let g:netrw_winsize = 25
 "----airline tabs for buffers-------
 let g:airline#extensions#tabline#enabled = 1
 let g:airline_theme = 'dark'
-"let g:tmuxline_powerline_separators = 0
-let g:airline_powerline_fonts = 1
+let g:tmuxline_powerline_separators = 0
+let g:airline_powerline_fonts = 0
 let mapleader = ";"
 set showcmd
 map <Leader>a :bn<cr>