Merge branch 'sg/merge-options' (early part)

* 'sg/merge-options' (early part):
  merge, pull: add '--(no-)log' command line option
  fmt-merge-msg: add '--(no-)log' options and 'merge.log' config variable
  add 'merge.stat' config variable
  merge, pull: introduce '--(no-)stat' option
  doc: moved merge.* config variables into separate merge-config.txt

contrib/completion/git-completion.bash

@@ -780,7 +780,7 @@ _git_merge ()
 		;;
 	--*)
 		__gitcomp "
-			--no-commit --no-summary --squash --strategy
+			--no-commit --no-stat --log --no-log --squash --strategy
 			"
 		return
 	esac