* Android Resolver: Added initial
  [Jetifier](https://developer.android.com/studio/command-line/jetifier)
  integration which simplifies
  [migration](ttps://developer.android.com/jetpack/androidx/migrate)
  to Jetpack ([AndroidX](https://developer.android.com/jetpack/androidx))
  libraries in cases where all dependencies are managed by the Android
  Resolver.
  This can be enabled via the `Use Jetifier` option in the
  `Assets > Play Services Resolver > Android Resolver > Settings` menu.
  Caveats:
  - If your project contains legacy Android Support Library .jar and .aar
    files, these files will need to be removed and replaced with references to
    artifacts on Maven via `*Dependencies.xml` files so that the Jetifier
    can map them to Jetpack (AndroidX) libraries.
    For example, remove the file `support-v4-27.0.2.jar` and replace it with
    `<androidPackage spec="com.android.support:support-v4:27.0.2"/>` in a
    `*Dependencies.xml` file.
  - If your project contains .jar or .aar files that use the legacy Android
    Support Libraries, these will need to be moved into a local Maven repo
    [See this guide](https://maven.apache.org/guides/mini/guide-3rd-party-jars-local.html)
    and then these files should be removed from your Unity project and instead
    referenced via `*Dependencies.xml` files so that the Jetifier can
    patch them to reference the Jetpack lirbaries.

Bug: 113575309
Change-Id: I83723cb5b2eaa4369beb454e498202285758af56

Added integration tests for the internal build system and
mainTemplate.gradle resolution modes when using the Jetifier.

https://github.com/googlesamples/unity-jar-resolver/issues/145
Bug: 135263921
Change-Id: I5c636050e29a2232755aa70049f82e4c51c45fc1

Auto-resolution was previously relying upon polling for differences in
runtime state which could break if the DLL was reloaded after settings
are changed.  This commit stores the resolution settings with the rest
of the state from the last resolution so that it's possible to
auto-resolve if any of this state changes or the settings change that
require resolution.

Bug: 135263921
Change-Id: I5858cebdb905f6425faee719032b830c9a066a81

This adds an option to enable Jetpack (AndroidX) Jetifier processing as
part of the either dependency resolution or Gradle builds.

This change also ensures that the user is notified of build environment
settings that will prevent the Jetifier from functioning or prevent the
use of the Jetpack (AndroidX) libraries.
See...
- https://developer.android.com/studio/releases/gradle-plugin#3-2-0
- https://developer.android.com/jetpack/androidx#using_androidx

https://github.com/googlesamples/unity-jar-resolver/issues/145
Bug: 135263921
Change-Id: Iddb2ab7e34b411973c761360e485aed2506f2ddc

The Jetifier requires the data binding library version to use, which is
the same version as the Android Gradle Plugin version. This commit
exposes a property which parses the Android Gradle Plugin version from
the Gradle build templates provided by Unity.

Bug: 135264177
Change-Id: I7780868d88d1810e615204abd820ddef348f7f11

Developers tend to move the plugin around in their project. However,
the Google.VersionHandler.dll asset GUID was changing with each release
resulting in the DLL failing to load if multiple versions are present in
the project. This patch fixes this issue by only generating new GUIDs
for files that are renamed in the plugin.

Bug: 127793909
Change-Id: I4569e467f3f0c1f96722a280d62af5916344af3e

com.android.support:multidex does not use the same versioning scheme
as other legacy Android support libraries so it should not be
version locked.

Bug: 135276990
Fixed #234

Change-Id: Idf567388cec68fca022022d14819df56a576254b

Added Jetifier support to the Gradle artifact downloader script.
download_artifacts.gradle can now substitute direct and transitive
dependencies on the legacy support libraries to Jetpack and rewrite
references to the legacy support libraries in all downloaded libraries.

This adds unit and integration tests for this functionality but does not
yet connect this to the Android Resolver Unity plugin.

https://github.com/googlesamples/unity-jar-resolver/issues/145
Bug: 113575309
Change-Id: Ibb92e43751425ebfd7cedfae62d275099860aaaa

This is required to use Kotlin plugins like the Jetifier with
Gradle's embedded Kotlin runtime.

https://github.com/googlesamples/unity-jar-resolver/issues/145
Bug: 113575309
Change-Id: I4d11d30d7944fb95a2c1c2f19f0762d55eda0024

Gradle now runs task execution in parallel by default but due to
https://github.com/gradle/gradle/issues/6068 it's not possible
to capture stdout / stderr from individual tasks which breaks
download_artifacts_test.gradle.  This commit modifies the test to run
all tasks serially, prepares for the Gradle bug to be fixed and
cleans up the output a little when tests fail.

https://github.com/googlesamples/unity-jar-resolver/issues/145
Bug: 113575309
Change-Id: Ifee400beaa4544b3d9145cce51b69125ffc1f5b9

* Android Resolver: Fix copying of .srcaar to .aar files for
  mainTemplate.gradle resolution.  PluginImporter configuration was previously
  not being applied to .aar files unless the Unity project was saved.

Change-Id: I597799035d928af3aad53e6c6ebc63bb14f47749

After modifing PluginImporter settings, assets need to be reimported
for the changes to be applied in some versions of Unity.

Reported in https://github.com/firebase/quickstart-unity/issues/377

Bug: 135125825

Change-Id: I6ca17391d3f89f213a8a21bea6613d3321ed7386

The warning has no context (i.e where the repo is referenced) and hence
only adds spam to the log.

Change-Id: I54588ac845ff35b235bea60e6bf1252a65db9c39

* Android Resolver: Fixed resolution of Android dependencies without version
  specifiers.
* Android Resolver: Fixed Maven repo not found warning in Android Resolver.
* Android Resolver: Fixed Android Player directory not found exception in
  Unity 2019.x when the Android Player isn't installed.

Change-Id: Idd553b1920975797ae9ffe97c8792b6fd7e2c5a9

Executing commands with POSIX paths fail on Windows, this
modifies the CommandLine module to converts path separators for the
tool (not the tool's arguments).

https://github.com/firebase/quickstart-unity/issues/379

Bug: 134758901
Change-Id: If591a21ab2c02f5e0005a10d554f4fbbf1dae799

Android Resolver's artifact downloader script was failing if a
dependency in the graph did not specify a version for an artifact.
This commit makes it possible to handle empty version specifications
in dependencies.

In addition, this adds more information to conflicting package log
messages and eliminates the creation of copy tasks for output
files that already exist.

Fixes #227
Bug: 134571587

Change-Id: I81d52d40c2447b6a6bfba68621fbd4b254570850

It was printing out "Repo directory %s not found" rather than
including the missing directory name in the message.

Change-Id: I5777450ffd1aaa6be8bdb5cefe73d0edc3b32430

Unity 2019.x throws an exception when
BuildPipeline.GetPlaybackEngineDirectory() is called and the Android player
isn't installed.  The Android build target can't be selected if it's not
installed, so we shouldn't be polling the build system if the build target
isn't Android.  This patch disables build system property polling on assembly
load if the build target isn't Android.

Fixes #220
Bug: 134665717

Change-Id: I147e51a9c7740d2e21fdd376abd7e6b2e7cdc7dc

* Android Resolver: Fixed exception due to Unity 2019.3.0a4 removing
  x86 from the set of supported ABIs.

Change-Id: I8a8f3fd91083b7c20fe66b48dc53c19eb5d73f0e

Unity 2019.3.0a4 removes support for x86_64 builds, removing the enum
value UnityEditor.AndroidArchitecture.  This results in an exception
being thrown during resolution.

Bug: 134137796
Fixes #224

Change-Id: I210c05d1f4bc9aa521b9ed61ed13159e504dac42

* Android Resolver: Added support for ABI stripping when using
  mainTemplate.gradle. This only works with AARs stored in repos
  on the local filesystem.

Change-Id: I2e1f00d09e365ab3204767010931530ac3ef985a

This will does not support removing libraries for unused ABIs in
AARs fetched from remote repos when using Android Gradle plugin
2.x.x.

Also, fixed handling moved maven repos in the project.

Bug: 133528579
Change-Id: I7a6fd807a03c0de7393fa6ce0f116817b9252794

Change-Id: Ib83668dcec58429df602d0acc27d0a46283e9f10

VersionHandlerImpl.RunOnMainThread() is pretty handy for editor
plugins so this exposes it.

Bug: 133495435
Change-Id: I8c5f38bf5f53efb53bf4071fdcc264105d1fcccc

* Android Resolver: If local repos are moved, the plugin will search the
  project for matching directories in an attempt to correct the error.
* Version Handler: Files can be now targeted to multiple build targets
  using multiple "gvh_" asset labels.
* Android Resolver: "implementation" or "compile" are now added correctly
  to mainTemplate.gradle in Unity versions prior to 2019.

Bug: 112525947
Bug: 133243196
Bug: 131903659
Change-Id: I63de34783612d12cee4031033c0693ab3be289e5

Some developers move plugins around in the project breaking local
maven repo paths.  This commit falls back to searching for local
maven repos if the directory isn't found, warning the user of the
file referencing the broken directory link along with the new
path.

Bug: 112525947
Change-Id: Ibfc2bc231904ccf93919edd9b5c78d0814e3d28b

BuildPipeline.GetPlaybackEngineDirectory() was added in Unity 2019
to get the playback engine directory.  The Android playback engine
directory is required to determine the version of Gradle shipped
with the plugin so this does not work in Unity < 2019.

This patch adds a compatible but slower way to retrieve the
AndroidPlayer directory which also fixes the generation of Gradle
dependency inclusion statements in Unity < 2019

Fixes #213
Bug: 133243196
Change-Id: I455ec6de28900a31ea414bd1ff657404e611b0fb

Change-Id: I39ff0409059c3970283c9541088b4e42464bdead

* Android Resolver: Added option to disable addition of dependencies to
  mainTemplate.gradle.
  See `Assets > Play Services Resolver > Android Resolver > Settings`.
* Android Resolver: Made paths to local maven repositories in
  mainTemplate.gradle relative to the Unity project when a project is not
  being exported.
* Android Resolver: Fixed builds with mainTemplate.gradle integration in
  Unity 2019.
* Android Resolver: Changed dependency inclusion in mainTemplate.gradle to
  use "implementation" or "compile" depending upon the version of Gradle
  included with Unity.
* Android Resolver: Gracefully handled exceptions if the console encoding
  can't be modified.
* Android Resolver: Now gracefully fails if the AndroidPlayer directory
  can't be found.

Change-Id: Ib9db961c1b41eddf817b9e1827da9206c01ca6ef

* Android Resolver: Added option to disable addition of dependencies to
  mainTemplate.gradle.
  See `Assets > Play Services Resolver > Android Resolver > Settings`.
* Android Resolver: Made paths to local maven repositories in
  mainTemplate.gradle relative to the Unity project when a project is not
  being exported.
* Android Resolver: Fixed builds with mainTemplate.gradle integration in
  Unity 2019.
* Android Resolver: Changed dependency inclusion in mainTemplate.gradle to
  use "implementation" or "compile" depending upon the version of Gradle
  included with Unity.
* Android Resolver: Gracefully handled exceptions if the console encoding
  can't be modified.
* Android Resolver: Now gracefully fails if the AndroidPlayer directory
  can't be found.

Bug: 127302270
Bug: 132915636
Bug: 133232328
Bug: 133243196
Bug: 133247696
Bug: 133261012
Bug: 133275965
Change-Id: If3f91d1d2f094fb117f9c35b53e86c287c598702

Unity 2019 changes the developer's Android project to a library when built by
Gradle.  The application project is now a launcher which includes this library.
However, when the application is built it doesn't include the repositories of
the developer's library project causing any repos added by the Android Resolver
to be ignored.  This commit fixes the issue by adding all Android Resolver
specified repositories to all top level Gradle projects.

In addition, this commit adds support for relative repo paths in
mainTemplate.gradle.

Bug: 133275965
Bug: 133261012
Change-Id: I863640bada62bd671bb68ebb1469490dba280311

This commit detects Gradle version redistributed by the Unity
and either includes dependencies using the "compile" statement or
"implementation" depending upon what is supported.

Fixes #213

Bug: 133243196
Change-Id: I5d6940b1c432196fe92e2df7163d676af1b05745

In some cases the console encoding can't be set
see c5335e2c .  In some versions
of Unity / Mono even setting a console encoding to it's current
value (i.e should do nothing) will throw an exception.  This
patch handles exceptions when trying restore console encoding.

Fixed #214
Bug: 127302270

Change-Id: I5869ddf00999a93f02a81343c18d2a5c68e5d599

Unity 2019 uses the 'com.android.library' plugin rather than
'com.android.application' which breaks the injection of maven repos
for referenced artifacts.  This commit fixes the issue by injecting
repos after either plugin statement is present in a gradle file.

Bug: 133247696
Change-Id: Ieda7c8c65a3eaecfdfefcd63655b086e0ec2a136

Some users want to use the old way of including dependencies when a
mainTemplate.gradle file is included in their Unity project.  This adds
an settings option to disable patching mainTemplate.gradle on
resolution.

Fixes #210

Bug: 132915636
Change-Id: Id75158333fdb4ad6a9ac97f11465458637968da9

In some cases developers have imported the Android resolver into
a Unity project where the install doesn't have an Android player
installed causing AndroidPlaybackEngineDirectory to continually
report an error.

Fixed #220

Bug: 133232328
Change-Id: I9f4a5973ec9e061bf50422e203c09d8fe7943ea3

* Version Handler: Fixed invocation of methods with named arguments.
* Version Handler: Fixed occasional hang when the editor is compiling
  while activating plugins.

Change-Id: I208ab1058ceaf20f8e4c2efc9985f703ef1809ac

Change-Id: Ia1f705b40cf57a2e1bda5d433b0276dd8a6ba0a9

InvokeMethod() was modified in ea3e8d81 to support method overloads
distiguished by type.  However, this change broke the lookup of methods
with named arguments.

Fixes #209
Bug: 132342024

Change-Id: I151fe5c893fbbc9b7feb0cf371b0e693a91e17bc