templater: factor out function that creates templater from string template
This function will host loading of template aliases. It is not defined at
templater, but at formatter, since formatter is the module handling ui stuff
in front of templater.
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ ls
a
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
B should disappear
$ ls
a