Merge branch 'rs/git-gui-use-modern-git-merge-syntax'

The original command line syntax for "git merge", which was "git
merge <msg> HEAD <parent>...", has been deprecated for quite some
time, and "git gui" was the last in-tree user of the syntax.  This
is finally fixed, so that we can move forward with the deprecation.

* rs/git-gui-use-modern-git-merge-syntax:
  git-gui: stop using deprecated merge syntax

git-gui/lib/merge.tcl

@@ -112,12 +112,7 @@ method _start {} {
 	close $fh
 	set _last_merged_branch $branch
 
-	set cmd [list git]
-	lappend cmd merge
-	lappend cmd --strategy=recursive
-	lappend cmd [git fmt-merge-msg <[gitdir FETCH_HEAD]]
-	lappend cmd HEAD
-	lappend cmd $name
+	set cmd [list git merge --strategy=recursive FETCH_HEAD]
 
 	ui_status [mc "Merging %s and %s..." $current_branch $stitle]
 	set cons [console::new [mc "Merge"] "merge $stitle"]