Add ability to specify version specification for commandline commands ...

As mentioned in the changelog, it was not possible with all commands.
No breaking changes are expected.

Normalize line endings & UTF8 BOMs

Merge pull request #2040 from omerfirmak/agora-1327 ...

Allow custom dflags to be defined for dependencies

Recursively apply dependencyBuildSettings ...

For now, only "dflags" is used

improve list command

Improved ldc cross compile: ...

The folder `.dub/obj` has been moved to `.dub/build-*/obj` for an independent cross / parallel build process.
Now it is possible that two processes can build the same project with different configurations.

Fix #2051 "Running unittests from dub single file packages fails" (#2052) ...

Performing test command dub imports every source file as module to build the project excluding the main source file. But this excluding may fail and in this case dub try to import the main source file as module. Single file package building fails because the main source file does not belong to any import path. Now both the current file and the main source file paths are compared in relative form to prevent importing the main source file as module.

Use DC env variable as the default compiler

Mutually exclude mainSourceFile of different configurations ...

Unless explicitly added to sourceFiles, a configuration will exclude
other configurations' mainSourceFile's.

Rebuild buildSettings after preGenerateCommand

cache the generated test main file: dub_test_root.d ...

these changes prevent dub from rebuilding a project every time it runs a unittest.

Improve output of toolchain requirements test, workaround heisenbug ...

There is currently an Heisenbug in Github CI where dub fails to run the program.
E.g. we see the following in the logs:
---
Performing "debug" build using ldc2 for x86_64.
dubtest1531 ~master: building configuration "application"...
Linking...
Running ../../../../../tmp/dubtest1531_2enU78/dubtest1531
Failed to execute program (No such file or directory)
[ERROR] -e:79 Did not pass with ldc="<=1.23.0"
[ERROR] Script failure.
---
This works around said bug by only building the package,
but not running it.

Testsuite: Replace --version=x.y.z with package@x.y.z

testsuite: Use built dub, not system one in more tests ...

Some places were missed during the last fixups.

Testsuite: Fix calls to die to always include line numbers ...

'die' actually taking two parameters seems to be a little-known fact.

version-spec: Use non-obsolete syntax for head/tail ...

This syntax is hardly documented, with the Linux manpage saying:
> For backwards compatibility, `-number` is equivalent to `-n number`.
http://schillix.sourceforge.net/man/man1/head.1.html
While some other man pages either don't mention it or call it obsolete.
For maximum compatibility, just use `-n 1`.

Make 'dub remove' remove all packages by default in non-interactive mode ...

Given how often it is used in the test-suite, it should be self-obvious
that it will be what most users want.

Fix some tests that were using installed DUB instead of built ones ...

Those tests were not actually testing the built dub,
but whatever was installed on the machine (or in the path) instead.

Remove redundant COND || false statement in tests

added version spec ability for remove and fetch commands, deprecate --version argument for those

Added version spec ability for dub commands

Update Vibe.d to v0.9.0 in test_registry

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

* Support dependencies as git url with exact commit

* Compare hashes for SCM

Fix issue 1917 - Add dub dustmite --no-redirect

Testsuite: Make timeout test properly fail on command not found ...

For example, if netcat is not installer, this test will happily pass.

Testsuite: Add no-test to copyFiles test ...

This test is only supposed to be run, not unittested.
It can create a problem when one wants to re-run the test suite,
as if the unittest have been built, there's an extra file in the bin directory,
which in turns makes the test fail.

testsuite: Use '|| true' when pipefail is involved ...

On Mac OSX, this script fails because of the behavior of pipefail.
A simple ' || true' solves the problem, while 'grep' still ensures
it behaves as expected.

testsuite: Replace a non-portable usage of rm (!) with dub clean ...

Who would have known that the following would pass on Linux but not Mac OSX:
---
touch file
rm -f file/nonono
---
Well surely not me. And indeed "b" is a file, not a directory,
so this rm didn't make sense. Just use dub clean. Like the rest of us.

testsuite: Skip gtkd test on non-Linux platform ...

This currently fails on Mac because the '.so' is hardcoded.
It should eventually be fixed, but for the time being,
my objective is to get things to pass on my machine.

testsuite: Make issue1117 test re-runnable ...

It's the little things in life, like being able to re-run your test-suite
on your own machine, that makes the greatest joy.