branchcache: use an explicit class for the v2 version
This prepare the introduction of an experimental v3 format version.
In the process, we move the description of the format in that new class.
$ for i in aaa zzz; do
> hg init t
> cd t
>
> echo
> echo "-- With $i"
>
> touch file
> hg add file
> hg ci -m "Add"
>
> hg cp file $i
> hg ci -m "a -> $i"
>
> hg cp $i other-file
> echo "different" >> $i
> hg ci -m "$i -> other-file"
>
> hg cp other-file somename
>
> echo "Status":
> hg st -C
> echo
> echo "Diff:"
> hg diff -g
>
> cd ..
> rm -rf t
> done
-- With aaa
Status:
A somename
other-file
Diff:
diff --git a/other-file b/somename
copy from other-file
copy to somename
-- With zzz
Status:
A somename
other-file
Diff:
diff --git a/other-file b/somename
copy from other-file
copy to somename