hgweb: add a floating tooltip to invite on followlines action
In followlines.js, we create a <div id="followlines-tooltip"> element to draw
attention of users on "followlines" feature. The element shows up on hover of
source lines after one second and follows the cursor. After first click (start
line selection), the text changes and indicates that next click will terminate
selection.
#require execbit
$ hg init repo
$ cd repo
$ echo foo > foo
$ chmod 644 foo
$ hg ci -qAm '644'
$ chmod 755 foo
$ hg ci -qAm '755'
reverting to rev 0
$ hg revert -a -r 0
reverting foo
$ hg st
M foo
$ hg diff --git
diff --git a/foo b/foo
old mode 100755
new mode 100644
$ cd ..