wireproto: introduce pusherr() to deal with "unsynced changes" error
The behaviour between http and ssh still differ:
- the "unsynced changes" is seen as a remote output in the http cases
- but it is correctly seen as a push error for ssh
$ 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