stream-clone: add a v3 version of the protocol
This new version is less rigid regarding the extract number of files and number
of bytes to be actually transfered, it also lays the groundwork for other
improvements.
The format stays experimental, but this is an interesting base to build upon.
#require symlink
https://bz.mercurial-scm.org/1438
$ hg init repo
$ cd repo
$ ln -s foo link
$ hg add link
$ hg ci -mbad link
$ hg rm link
$ hg ci -mok
$ hg diff -g -r 0:1 > bad.patch
$ hg up 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg import --no-commit bad.patch
applying bad.patch
$ hg status
R link
? bad.patch