progress: move the singleton logic to the ui module
The use of a singleton for all of progress handling is debatable (because
config may vary). However this is how the extension has been doing it so far.
We move that code into the ui module because this is where is should belong when
progress is moved into core.
$ cat > unix2mac.py <<EOF
> import sys
>
> for path in sys.argv[1:]:
> data = file(path, 'rb').read()
> data = data.replace('\n', '\r')
> file(path, 'wb').write(data)
> EOF
$ cat > print.py <<EOF
> import sys
> print(sys.stdin.read().replace('\n', '<LF>').replace('\r', '<CR>').replace('\0', '<NUL>'))
> EOF
$ hg init
$ echo '[hooks]' >> .hg/hgrc
$ echo 'pretxncommit.cr = python:hgext.win32text.forbidcr' >> .hg/hgrc
$ echo 'pretxnchangegroup.cr = python:hgext.win32text.forbidcr' >> .hg/hgrc
$ cat .hg/hgrc
[hooks]
pretxncommit.cr = python:hgext.win32text.forbidcr
pretxnchangegroup.cr = python:hgext.win32text.forbidcr
$ echo hello > f
$ hg add f
$ hg ci -m 1
$ python unix2mac.py f
$ hg ci -m 2
attempt to commit or push text file(s) using CR line endings
in dea860dc51ec: f
transaction abort!
rollback completed
abort: pretxncommit.cr hook failed
[255]
$ hg cat f | python print.py
hello<LF>
$ cat f | python print.py
hello<CR>