From: Xing Xin <xingxin.xx@bytedance.com>

When using the bundle-uri mechanism with a bundle list containing
multiple interrelated bundles, we encountered a bug where tips from
downloaded bundles were not being discovered, resulting in rather slow
clones. This was particularly problematic when employing the heuristic
`creationTokens`.

And this is easy to reproduce. Suppose we have a repository with a
single branch `main` pointing to commit `A`, firstly we create a base
bundle with

  git bundle create base.bundle main

Then let's add a new commit `B` on top of `A`, so that an incremental
bundle for `main` can be created with

  git bundle create incr.bundle A..main

Now we can generate a bundle list with the following content:

  [bundle]
      version = 1
      mode = all
      heuristic = creationToken

  [bundle "base"]
      uri = base.bundle
      creationToken = 1

  [bundle "incr"]
      uri = incr.bundle
      creationToken = 2

A fresh clone with the bundle list above would give the expected
`refs/bundles/main` pointing at `B` in new repository, in other words we
already had everything locally from the bundles, but git would still
download everything from server as if we got nothing.

So why the `refs/bundles/main` is not discovered? After some digging I
found that:

1. when unbundling a downloaded bundle, a `verify_bundle` is called to
   check its prerequisites if any. The verify procedure would find oids
   so `packed_git` is initialized.

2. after unbundled all bundles, we would enter `do_fetch_pack_v2`,
   during which `mark_complete_and_common_ref` and `mark_tips` would
   find oids with `OBJECT_INFO_QUICK` flag set, so no new packs would be
   enlisted if `packed_git` has already initialized in 1.

Back to the example above, when unbunding `incr.bundle`, `base.pack` is
enlisted to `packed_git` bacause of the prerequisites to verify. Then we
can not find `B` for negotiation at a latter time bacause `B` exists in
`incr.pack` which is not enlisted in `packed_git`.

This commit fixes this by adding a `reprepare_packed_git` call for every
successfully unbundled bundle, which ensures to enlist all generated
packs from bundle uri. And a set of negotiation related tests are added.

Signed-off-by: Xing Xin <xingxin.xx@bytedance.com>

Submitted-As: https://lore.kernel.org/git/pull.1730.git.1715742069966.gitgitgadget@gmail.com