largefiles: add support for 'largefiles://' url scheme
This changesets allows Mercurial to transparently download content from the
configured largefile store. This handle all authentication and largefile
protocol details.
The target usecase is to leverage largefile infrastructure for clone bundle. See
next changeset for details
#require symlink
https://bz.mercurial-scm.org/1438
$ hg init
$ 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