amend! Merge pull request #410: Sparse Index: latest integrations

Merge pull request #410: Sparse Index: latest integrations

```
6e74958 p2000: add 'git checkout -' test and decrease depth
3e1d03c p2000: compress repo names
cd94f82 commit: integrate with sparse-index
65e79b8 sparse-index: recompute cache-tree
e9a9981 checkout: stop expanding sparse indexes
4b801c8 t1092: document bad 'git checkout' behavior
71e3015 unpack-trees: resolve sparse-directory/file conflicts
5e96df4 t1092: test merge conflicts outside cone
defab1b add: allow operating on a sparse-only index
9fc4313 pathspec: stop calling ensure_full_index
0ec03ab add: ignore outside the sparse-checkout in refresh()
adf5b15 add: remove ensure_full_index() with --renormalize
```

These commits are equivalent to those already in `next` via gitgitgadget#999.

```
80b8d6c Merge branch 'sparse-index/add' into stolee/sparse-index/add
```

This merge resolves conflicts with some work that happened in parallel, but is already in upstream `master`.

```
c407b2c t7519: rewrite sparse index test
9dad0d2 sparse-index: silently return when not using cone-mode patterns
2974920 sparse-index: silently return when cache tree fails
e7cdaa0 unpack-trees: fix nested sparse-dir search
347410c sparse-checkout: create helper methods
4537233 attr: be careful about sparse directories
5282a86 sparse-index: add SPARSE_INDEX_MEMORY_ONLY flag
3a2f316 sparse-checkout: clear tracked sparse dirs
fb47b56 sparse-checkout: add config to disable deleting dirs
```

These commits are the ones under review as of gitgitgadget#1009. Recent review made this less stable. It's a slightly different and more robust version of #396.

> Note: I'm still not done with the feedback for upstream, but the remaining feedback is "can we add tests that cover these tricky technical bits?" and in `microsoft/git` these are already covered by the Scalar functional tests (since that's how they were found).

```
080b02c diff: ignore sparse paths in diffstat
d91a647 merge: make sparse-aware with ORT
df49b5f merge-ort: expand only for out-of-cone conflicts
cdecb85 t1092: add cherry-pick, rebase tests
0c1ecfb sequencer: ensure full index if not ORT strategy
406dfbe sparse-index: integrate with cherry-pick and rebase
```

These commits integrate with `git merge`, `git cherry-pick`, `git revert`, and `git rebase` as of gitgitgadget#1019. This got some feedback that changed how the tests were working so they are more robust. This led to a new commit (0c1ecfb).

```
cbb0ab3 Merge branch 'sparse-index/merge' into vfs-2.33.0
acb8623 t7524: test no longer fails
```

Finally, the commits are merged into `vfs-2.33.0` and also we include a fix to a `microsoft/git` test that is no longer broken.