Add unittest to test collection of C sources and headers

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.

Trivial: Remove test about the internals of Dependency ...

Now that Dependency is a proper SumType, this can never happen.

Integrate `dependencyBuildSettings` into dependencies ...

Because those are specified in `dependencies`,
they should be stored alongside them.
Unfortunately this will slihtly increase memory usage in the common case,
but unlikely to a point where it would be problematic.

This is technically a breaking change as a field is getting removed,
however this struct has been manipulated a few times in breaking ways,
and it's unlikely `dependencyBuildSettings` is being used outside of dub,
given how recent it is and how narrow its usage is.
However, as `dependencies` is likely to be widely used, a compatibility
type and an `alias this` are provided not to break client code.

Deprecate Dependency.versionSpec ...

All places which assumed that Dependency contained a VersionRange have been culled,
so we can now start removing those properties.

SDL: Use visit instead of multiple if when parsing Dependency

Keep logging functionality out of the public API as requested in https://github.com/dlang/dub/pull/2124#issuecomment-813016939.

New logging module - initial functionality ...

The new module replaces dub.internal.vibecompat.core.log by using the
same function names, but implementing colored output and the left
fixed-width tag. Overloaded functions are provided to output colored
text.

Still missing initLogging() and non-TTY stdout/stderr detection

sdl: Simplify Dependency parsing ...

Don't warn on ignored version specification, json doesn't do this.
Also fully replace the instance instead of editing piece-meal,
it makes the code clearer.

Dependency: Move `spec` / git ref inside of `Repository` ...

The `Dependency` struct is logically acting as an `enum`,
with 3 discrete possibilities. However, some of the logic is
piggybacking on the (original) version logic.
`Repository` is one of them, and by separating things,
we can make stronger assumptions in `Version` and `Dependency`.

Remove leading hyphen in platform specs ...

It doesn't serve any purpose.

Move fix for issue 711 outside of JSON/SDL parser ...

Having the fix for this issue in the parser means adding non-trivial logic.
It is easier to reason about to have this logic done as a post-processing step,
replacing the `autodetect` with the actually auto-detected version.
This also paves the way to have other `targetType` as default,
e.g. the `unittest` configuration should probably not be `library`.

sdl/json: Do not create dummy dependencyBuildSettings entry ...

Because if a user provide an object as a dependency,
such as `{ "path": "foo/bar", "optional": true }`,
we would create a dummy entry in the AA.

sdl: Do not use deprecated aliases ...

Those usages were forgotten when the deprecation was implemented,
as they didn't show up with dub build, only dub test.

Implement injection of source files from dependencies into parent final binaries (executed/shared libraries)

Add environment variables to BuildSettings (#2121)

merge stable (#2106) ...

* Allow adding dflags on dependencies when using SDL format

Fixes #2079

* update version to v1.24.1-beta.1

Co-authored-by: Ömer Faruk IRMAK <omerfirmak@gmail.com>

Replace occurences of 'in ref' with 'const scope ref' ...

In support for dlang/dmd#11000

Support dependencies as git url with exact commit (#1798) ...

* Support dependencies as git url with exact commit

* Compare hashes for SCM

Remove some unused variables ...

There are plenty left, but those ones didn't seem to have any side effect.

fix: report correct line on sdl error

Change toolchainRequirements fields to Dependency. ...

Also removes some API clutter from Compiler and PackageRecipe.

Merge pull request #1571 from rtbo/requirements ...

toolchainRequirements recipe support
merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>

toolchainRequirements recipe support

extraDependencyFiles attribute added

Added experimental build settings to filter applicable version identifiers ...

Those settings allow to filter version identifiers and debug version identifiers
used during building a package. This can improve the build cache efficiency for
libraries that are used by multiple applications with different version
identifiers.

- only merge filters from source dependencies when the
  dependent has an explicit filter list as well

Pre/post run commands added

Revert "implement "minDubVersion" field"

implement minDubVersion check ...

fix #1531

Rename Path to NativePath. ...

Matches the changes done in vibe.d 0.8.x and vibe-core.