commands: support consuming stream clone bundles
For the same reasons that we don't produce stream clone bundles with `hg
bundle`, we don't support consuming stream clone bundles with `hg
unbundle`. We introduce a complementary debug command for applying
stream clone bundles. This command is mostly to facilitate testing.
Although it may be used to manually apply stream clone bundles until a
more formal mechanism is (possibly) adopted.
$ hg init
$ echo 123 > a
$ hg add a
$ hg commit -m "first" a
$ mkdir sub
$ echo 321 > sub/b
$ hg add sub/b
$ hg commit -m "second" sub/b
$ cat sub/b
321
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat sub/b 2>/dev/null || echo "sub/b not present"
sub/b not present
$ test -d sub || echo "sub not present"
sub not present