templatefilters: wrap all filters in dedicated functions
This will highly simplify the docstring integration. I measured "hg log
--style=changelog" duration on mercurial itself and could not detect any
difference.
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls
a
unknown