mergetool: reorder vim/gvim buffers in three-way diffs
When invoking default (g)vimdiff three-way merge, the merged file is
loaded as the first buffer but moved to the bottom as the fourth window.
This causes a disconnect between vim commands that operate on window
positions (e.g. CTRL-W_w) and those that operate on buffer index (e.g.
do/dp).
This change reorders the buffers to have the same index as windows while
keeping the cursor default to the merged result as the bottom window.
Signed-off-by: Dickson Wong <dicksonwong@gmail.com>
Tested-by: Michael J Gruber <git@drmicha.warpmail.net>
Acked-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>