Merge branch 'rs/work-around-grep-opt-insanity'

* rs/work-around-grep-opt-insanity:
  Protect scripted Porcelains from GREP_OPTIONS insanity
  mergetool--lib: simplify guess_merge_tool()

Conflicts:
	git-instaweb.sh

git-rebase.sh

@@ -467,7 +467,7 @@ orig_head=$branch
 mb=$(git merge-base "$onto" "$branch")
 if test "$upstream" = "$onto" && test "$mb" = "$onto" &&
 	# linear history?
-	! (git rev-list --parents "$onto".."$branch" | grep " .* ") > /dev/null
+	! (git rev-list --parents "$onto".."$branch" | sane_grep " .* ") > /dev/null
 then
 	if test -z "$force_rebase"
 	then