fetch: Support multiple arguments, projects, recursive fetch ...

Dub fetch was overly limited for no reason: Since we migrated from
`--version` to `name@version`, there is no reason to only allow one
argument, multiple packages can be fetched. Additionally, it could
be useful to fetch a package's dependency without building it,
which the command now supports.

Provide a consistent experience when interacting with dub fetch ...

'dub fetch doesNotExists' and 'dub fetch doesNotExists@1.0.0'
were behaving differently, both when they succeeded and when
they failed. Making them consistent was just a matter of deleting
a few lines of code, allowing us to also remove a branch.

Fix #2706: Dub run ignores locally registered packages ...

The code was overly complicated and failed to do what it intended.
If a version was provided, it would always call 'fetch' even though
getBestPackage would have returned something.
Assuming that sub-packages are always present is also not working,
as the following would fail:
$ rm -rf ~/.dub/packages/vibe-d && dub run vibe-d:data
    Warning Package 'vibe-d:data' was neither found locally nor online.
The new code is both shorter and simpler, taking advantage
of the various improvements made to the APIs over the year
(for example, getBestPackage with VersionRange.Any does the right thing).

CommandLine: Make better use of UserPackageDesc

CommandLine: Rename PackageAndVersion, slightly refactor, document

CommandLine: Store a VersionRange, not a string, in PackageAndVersion ...

Typing this parameter means that places know they have a valid
version on their hand as opposed to a string everyone need to
validate and verify.

Deprecate Project.packageManager ...

There is no reason to expose the PackageManager through the Project.
In fact, the only two places it was used were in generators,
where the PackageManager was stored but never used.
The generators arguably should not have access to the PackageManager,
as all the Packages should have been loaded and handled to them
before the generation starts.

Remove fallback to ~master on dub fetch, fix #2679 ...

The retry does not make sense, as one cannot add a package
to the registry without a release version.
It is also not in line with Dub strategy, as we are trying
to reduce the usage of branch dependencies.

This also fixes issue #2679 which pointed out the error message
was sub-par. The API of the registry seems to have changed and
we now get `null` instead of `undefined`, leading to an error
inside the JSON module instead of the enforce being triggered.

Trivial: Remove dead existsFile import ...

It is not used in this function.

Remove unused iterateDirectory(string) ...

It was actually unused, because al the call sites were doing a useless
round-trip from NativePath to string to NativePath.
There is no need for it anymore so we can just remove it to avoid
this kind of mistakes in the future.

Fix issue #2190 - windows: dub won't run if TEMP is unset or empty

interactively query for license, suggest SPDX licenses (#1902) ...

Co-authored-by: Martin Nowak <code@dawg.eu>

add --deep flag to `dub build` ...

Allows to build all dependencies of a static library

Implemented recipe files for dub #2684 (#2685) ...

Co-authored-by: Jan Jurzitza <gh@webfreak.org>

support specifying --d-versions ...

Usually you should prefer using configurations and build types, but
sometimes, especially when wrapped in other build tools or when
supporting e.g. different target platforms on the same target
architecture and configuration, you may want to manually manage certain
versions.

Fix #2574: Suggest alternative spelling when a command is mistyped (#2593) ...

Co-authored-by: WebFreak001 <gh@webfreak.org>

Merge remote-tracking branch 'upstream/stable' into merge_stable

Make `dub run --root=x` default app CWD in dub CWD ...

Fix #2582

fix typo(s)

Merge remote-tracking branch 'upstream/stable' into merge_stable

reduce dependency on the working directory ...

Improves library API usage and bugs with the build generator

replace std.variant with std.sumtype (#2550) ...

Variant is quite big and runtime heavy, with sumtype we already cover
wrong type cases at compile time.

Implement --color=auto|always|never, fix #2410 (#2552) ...

* Implement --color=auto|always|never, fix #2410

Also improves error message output for unsupported --color values.

* fix compile error with certain D versions

Use a central build cache for all build artifacts ...

Currently the central build cache is not configurable,
but as most build artifacts end up in `~/.dub/packages/` anyway,
this will be a positive change for users.

Fixed dub init docs (#2537)

Improve dub init custom template docs

Replace all instances of mkdirRecurse with ensureDir ...

All usages actually want to ensure the directory is present,
and don't care about having a separation between existence check
and creation.

Move foreign code from global scope to dub.internal. ...

Avoids conflicting with the actual dub packages when working with dub as a library. Also, even if just by convention, it ensures that dependent code doesn't rely on this code as a public API.

Do not use Phobos' sumtype, use dyaml's versioned one ...

So that we can compile with older versions of the frontend,
currently v2.097 instead of v2.098.

Dub: Deprecate changing the rootPath ...

It's an essential part of the setup, and too many properties are derived
from it that we don't want to let the library user the ability to mess with it.