This PR uses borrowed data in `BuildDispatch` which makes creating a
`BuildDispatch` extremely cheap (only one allocation, for the Python
executable). I can be talked out of this, it will have no measurable
impact.
## Summary
This PR enables overrides to be passed to `pip-compile` and
`pip-install` via a new `--overrides` flag.
When overrides are provided, we effectively replace any requirements
that are overridden with the overridden versions. This is applied at all
depths of the tree.
The merge semantics are such that we replace _all_ requirements of a
package with _all_ requirements from the overrides files. So, for
example, if a package declares:
```
foo >= 1.0; python_version < '3.11'
foo < 1.0; python_version >= '3.11'
```
And the user provides an override like:
```
foo >= 2.0
```
Then _both_ of the `foo` requirements in the package will be replaced
with the override.
If instead, the user provided an override like:
```
foo >= 2.0; python_version < '3.11'
foo < 3.0; python_version >= '3.11'
```
Then we'd replace _both_ of the original `foo` requirements with both of
these overrides. (In technical terms, for each package in the
requirements file, we flat-map over its overrides.)
Closes https://github.com/astral-sh/puffin/issues/511.
After this change, two wheel caches remain: `built-wheels-v0` and
`wheels-v0`, docs screenshots below. Each contains both the wheel
metadata, cache policy and zip or unzipped wheels under the same name.
The zipped/unzipped strategy is as follows: In `pip-compile`, when we
build a wheel, we store it zipped. When `pip-sync` or a source dist
build in `pip-compile` need to install the wheel, we unzip it, remove
the file and replace it with the unzipped wheel.
This removes `WheelCache` and `UrlIndex` in favor of `Cache` plus
`WheelCache`. The non-built wheel cache now considers index urls and the
url for url wheels.
I'm unsure if we need the `Unzipper` type, this could just be a
function.
I move `no_index` into `IndexUrls` and started using `IndexUrl` up to
the clap level.
I left a number of TODOs in the code, namely performing the actual
invalidation of unzipped wheels and making the `InstallPlan` understand
cache invalidation (i.e. uninstall wheels when their remote changed).

This is mostly a mechanical refactor that moves 80% of our code to the
same cache abstraction.
It introduces cache `Cache`, which abstracts away the path of the cache
and the temp dir drop and is passed throughout the codebase. To get a
specific cache bucket, you need to requests your `CacheBucket` from
`Cache`. `CacheBucket` is the centralizes the names of all cache
buckets, moving them away from the string constants spread throughout
the crates.
Specifically for working with the `CachedClient`, there is a
`CacheEntry`. I'm not sure yet if that is a strict improvement over
`cache_dir: PathBuf, cache_file: String`, i may have to rotate that
later.
The interpreter cache moved into `interpreter-v0`.
We can use the `CacheBucket` page to document the cache structure in
each bucket:

Preparing for #235, some refactoring to `puffin_interpreter`.
* Added a dedicated error type instead of anyhow
* `InterpreterInfo` -> `Interpreter`
* `detect_virtual_env` now returns an option so it can be chained for
#235
## Summary
This is a refactor to address a TODO in the build context whereby we
aren't respecting the resolution options in recursive resolutions. Now,
the options are split out from the resolution _manifest_, and shared
across the build context tree.
This script can compare different requirements between pip(-compile) and
puffin across python versions, with debug and release builds.
Examples:
```shell
scripts/compare_with_pip/compare_with_pip.py
scripts/compare_with_pip/compare_with_pip.py -p 3.10
scripts/compare_with_pip/compare_with_pip.py --release -p 3.9 --target 'transformers[deepspeed-testing,dev-tensorflow]'
```
It found a bunch of fixed bugs, e.g. the lack of yanked package handling
and source dist handling, as well as #423, which is currently most of
the output.
Example output:
https://gist.github.com/konstin/9ccf8dc7c2dcca737bf705429ced4892#443 should be merged first
Always¹ clear the temporary directories we create.
* Clear source dist downloads: Previously, the temporary directories
would remain in the cache dir, now they are cleared properly
* Clear wheel file downloads: Delete the `.whl` file, we only need to
cache the unpacked wheel
* Consistent handling of cache arguments: Abstract the handling for CLI
cache args away, again making sure we remove the `--no-cache` temp dir.
There are no more `into_path()` calls that persist `TempDir`s that i
could find.
¹Assuming drop is run, and deleting the directory doesn't silently
error.
I intend this to become the main form of caching for puffin: You can
make http requests, you tranform the data to what you really need, you
have control over the cache key, and the cache is always json (or
anything else much faster we want to replace it with as long as it's
serde!)
By default, we will build source distributions for both resolving and
installing, running arbitrary code. `--no-build` adds an option to ban
this and only install from wheels, no source distributions or git builds
allowed. We also don't fetch these and instead report immediately.
I've heard from users for whom this is a requirement, i'm implementing
it now because it's helpful for testing.
I'm thinking about adding a shared `PuffinSharedArgs` struct so we don't
have to repeat each option everywhere.
This PR makes the cache non-optional in most of Puffin, which simplifies
the code, allows us to reuse the cache within a single command (even
with `--no-cache`), and also allows us to use the cache for disk storage
across an invocation.
I left the cache as optional for the `Virtualenv` and `InterpreterInfo`
abstractions, since those are generic enough that it seems nice to have
a non-cached version, but it's kind of arbitrary.
Show the resolution in a concise format for puffin-dev. Note that this
doesn't affect the main puffin output, it's just more convenient for me
when developing.