https://hg.mozilla.org/ upgraded to Mercurial 4.4

[Gregory Szorc]

After a long-overdue upgrade, https://hg.mozilla.org/ is now running
Mercurial 4.4 (from 4.2.3).

Only the https:// endpoint has been upgraded: ssh://hg.mozilla.org/ is
still running Mercurial 4.2.3.

Notable changes:

* The UI of the line history functionality has been tweaked (hopefully for
the better)
* The line history tool now works on annotate pages - not just file view
pages - e.g. https://hg.mozilla.org/mozilla-central/annotate/tip/mach
* Annotate pages have checkboxes to control how whitespace is treated when
computing annotations (you can also adjust these URL query string
parameters for the json-annotate endpoint as well)
* Phases data is now transferred with other data and doesn't require an
additional HTTP request to retrieve, making `hg pull` operations faster.

As a reminder, to use the line history tool, open a file or annotate page.
When you move your mouse cursor over a line, you should see a "+-" icon on
the left of the line. Click that icon once to choose a line. Then move your
cursor and click the "+-" on another line. You'll see a box with links to
take you to the history of the lines you selected. e.g.
https://hg.mozilla.org/mozilla-central/log/tip/mach?patch=&linerange=77:82.
The line history feature is super useful for looking at the history of a
function. If you do code archeology, this is a feature that once you start
using, you won't know how you managed to live without it.

And as a general reminder, we can customize the HTML of hg.mozilla.org
pretty easily. If you want a piece of data somewhere to make your life
easier, that's the kind of thing that can be hacked on pretty easily during
an all hands meeting.

If you see any problems, make noise in #vcs or file something blocking the
"hg44" bug. If it is urgent, don't hesitate to look up my number in the
phonebook and page me.