tests/test-debugbackupbundle.t

rust-index: using `hg::index::Index` in `hg-cpython::dagops`

Hooking `headrevs` to the Rust index is straightforward as long as
we go the `PySharedRef` way. Direct attempts of obtaining a reference
to the inner `hg::index::Index` fail for lifetime reasons: the reference
is bound to the GIL, yet the `as_set` local variable is considered to
be static (the borrow checker clearly does not realize or care that this
set only stores `Revision` values).

In `rank()`, the chosen solution is the simplest as far as `hg-cpython` is
concerned, but it has the defect of removing an implementation
that would be easily adaptable if the core index did implement `RankedGraph`
(returning the same error as long as only `REVLOGV1` is supported), but that
would introduce a direct dependency of `hg-core` on the ``vcsgraph` crate.

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > strip=
  > EOF

Setup repo

  $ hg init repo
  $ cd repo

Test backups list and recover

  $ hg debugbackupbundle
  no backup changesets found

  $ mkcommit() {
  >    echo "$1" > "$1"
  >    hg add "$1"
  >    hg ci -l $1
  > }
  $ mkcommit a
  $ mkcommit b
  $ hg strip .
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/repo/.hg/strip-backup/d2ae7f538514-2953539b-backup.hg
  $ hg debugbackupbundle
  Recover changesets using: hg debugbackupbundle --recover <changeset hash>
  
  Available backup changesets:
  * (glob)
  d2ae7f538514 b

  $ hg debugbackupbundle --recover d2ae7f538514
  Unbundling d2ae7f538514
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  new changesets d2ae7f538514 (1 drafts)