mercurial.el: change default log range to tip:0 If the tip revision is smaller than hg-rev-completion-limit (defaults to 100), "hg log -r tip:-100" fails. Since performance does not differ between "hg log -l 50 -r tip:0" and "hg log -l 50 -r tip:-100" even on large repository, default range can be changed from "tip:-100" to "tip:0" without any drawbacks.