aliases: git: consistent behavior for git users

The case block in git.aliases.bash does the right thing for vim users
that do not populate $EDITOR.  However vim users that populate $EDITOR
are met with the following error:

$ gd
Vim: Warning: Input is not from a terminal
Vim: Error reading input, exiting...
Vim: preserving files...
Vim: Finished.

Fix this inconsistency by adding another case block in the else block
which handles passing the appropriate arguments to vim.

Signed-off-by: Michael Turquette <mturquette@deferred.io>

aliases/available/git.aliases.bash

@@ -47,5 +47,11 @@ if [ -z "$EDITOR" ]; then
         ;;
     esac
 else
-    alias gd="git diff | $EDITOR"
+    case $EDITOR in
+      *vim*)
+        alias gd="git diff | $EDITOR -R -"
+        ;;
+      *)
+        alias gd="git diff | $EDITOR"
+    esac
 fi