External Dependency Manager for Unity

Overview

The External Dependency Manager for Unity (EDM4U)
(formerly Play Services Resolver / Jar Resolver) is intended to be used by any
Unity plugin that requires:

Android specific libraries (e.g
AARs).
iOS CocoaPods.
Version management of transitive dependencies.
Management of Package Manager (PM) Registries.

Updated releases are available on
GitHub

Background

Many Unity plugins have dependencies upon Android specific libraries, iOS
CocoaPods, and sometimes have transitive dependencies upon other Unity plugins.
This causes the following problems:

Integrating platform specific (e.g Android and iOS) libraries within a
Unity project can be complex and a burden on a Unity plugin maintainer.
The process of resolving conflicting dependencies on platform specific
libraries is pushed to the developer attempting to use a Unity plugin.
The developer trying to use you plugin is very likely to give up when
faced with Android or iOS specific build errors.
The process of resolving conflicting Unity plugins (due to shared Unity
plugin components) is pushed to the developer attempting to use your Unity
plugin. In an effort to resolve conflicts, the developer will very likely
attempt to resolve problems by deleting random files in your plugin,
report bugs when that doesn't work and finally give up.

EDM provides solutions for each of these problems.

Android Dependency Management

The Android Resolver component of this plugin will download and integrate
Android library dependencies and handle any conflicts between plugins that share
the same dependencies.

Without the Android Resolver, typically Unity plugins bundle their AAR and
JAR dependencies, e.g. a Unity plugin SomePlugin that requires the Google
Play Games Android library would redistribute the library and its transitive
dependencies in the folder SomePlugin/Android/. When a user imports
SomeOtherPlugin that includes the same libraries (potentially at different
versions) in SomeOtherPlugin/Android/, the developer using SomePlugin and
SomeOtherPlugin will see an error when building for Android that can be hard
to interpret.

Using the Android Resolver to manage Android library dependencies:

Solves Android library conflicts between plugins.
Handles all of the various processing steps required to use Android
libraries (AARs, JARs) in Unity 4.x and above projects. Almost all
versions of Unity have - at best - partial support for AARs.
(Experimental) Supports minification of included Java components without
exporting a project.

iOS Dependency Management

The iOS Resolver component of this plugin integrates with
CocoaPods to download and integrate iOS libraries
and frameworks into the Xcode project Unity generates when building for iOS.
Using CocoaPods allows multiple plugins to utilize shared components without
forcing developers to fix either duplicate or incompatible versions of
libraries included through multiple Unity plugins in their project.

Package Manager Registry Setup

The Package Manager
(PM) makes use of NPM registry servers for package
hosting and provides ways to discover, install, upgrade and uninstall packages.
This makes it easier for developers to manage plugins within their projects.

However, installing additional package registries requires a few manual steps
that can potentially be error prone. The Package Manager Resolver
component of this plugin integrates with
PM to provide a way to
auto-install PM package registries when a .unitypackage is installed which
allows plugin maintainers to ship a .unitypackage that can provide access
to their own PM registry server to make it easier for developers to
manage their plugins.

Unity Plugin Version Management

Finally, the Version Handler component of this plugin simplifies the process
of managing transitive dependencies of Unity plugins and each plugin's upgrade
process.

For example, without the Version Handler plugin, if:

Unity plugin SomePlugin includes EDM4U plugin at
version 1.1.
Unity plugin SomeOtherPlugin includes EDM4U
plugin at version 1.2.

The version of EDM4U included in the developer's project depends upon the
order the developer imports SomePlugin or SomeOtherPlugin.

This results in:

EDM4U at version 1.2, if SomePlugin is imported then SomeOtherPlugin
is imported.
EDM4U at version 1.1, if SomeOtherPlugin is imported then
SomePlugin is imported.

The Version Handler solves the problem of managing transitive dependencies by:

Specifying a set of packaging requirements that enable a plugin at
different versions to be imported into a Unity project.
Providing activation logic that selects the latest version of a plugin
within a project.

When using the Version Handler to manage EDM4U included in SomePlugin and
SomeOtherPlugin, from the prior example, version 1.2 will always be the
version activated in a developer's Unity project.

Plugin creators are encouraged to adopt this library to ease integration for
their customers. For more information about integrating EDM4U
into your own plugin, see the Plugin Redistribution
section of this document.

Analytics

The External Dependency Manager for Unity plugin by default logs usage to Google
Analytics. The purpose of the logging is to quantitatively measure the usage of
functionality, to gather reports on integration failures and to inform future
improvements to the developer experience of the External Dependency Manager
plugin. Note that the analytics collected are limited to the scope of the EDM4U
plugin’s usage.

For details of what is logged, please refer to the usage of
EditorMeasurement.Report() in the source code.

Requirements

The Android Resolver and iOS Resolver components of the plugin only work
with Unity version 4.6.8 or higher.

The Version Handler component only works with Unity 5.x or higher as it
depends upon the PluginImporter UnityEditor API.

The Package Manager Resolver component only works with
Unity 2018.4 or above, when
scoped registry
support was added to the Package Manager.

Getting Started

Before you import EDM4U into your plugin project, you first
need to consider whether you intend to redistribute EDM4U
along with your own plugin.

Plugin Redistribution

If you're a plugin maintainer, redistributing EDM4U inside your own plugin
will ease the integration process for your users, by resolving dependency
conflicts between your plugin and other plugins in a user's project.

If you wish to redistribute EDM4U inside your plugin,
you must follow these steps when importing the
external-dependency-manager-*.unitypackage, and when exporting your own plugin
package:

Import the external-dependency-manager-*.unitypackage into your plugin
project by
running Unity from the command line, ensuring that
you add the -gvh_disable option.
Export your plugin by running Unity from the command line, ensuring that
you:
- Include the contents of the Assets/PlayServicesResolver and
  Assets/ExternalDependencyManager directory.
- Add the -gvh_disable option.

You must specify the -gvh_disable option in order for the Version
Handler to work correctly!

For example, the following command will import the
external-dependency-manager-1.2.46.0.unitypackage into the project
MyPluginProject and export the entire Assets folder to
MyPlugin.unitypackage:

Unity -gvh_disable \
      -batchmode \
      -importPackage external-dependency-manager-1.2.46.0.unitypackage \
      -projectPath MyPluginProject \
      -exportPackage Assets MyPlugin.unitypackage \
      -quit

Background

The Version Handler component relies upon deferring the load of editor DLLs
so that it can run first and determine the latest version of a plugin component
to activate. The build of EDM4U plugin has Unity asset metadata that is
configured so that the editor components are not initially enabled when it's
imported into a Unity project. To maintain this configuration when importing
the external-dependency-manager.unitypackage into a Unity plugin project, you
must specify the command line option -gvh_disable which will prevent the
Version Handler component from running and changing the Unity asset metadata.

Android Resolver Usage

The Android Resolver copies specified dependencies from local or remote Maven
repositories into the Unity project when a user selects Android as the build
target in the Unity editor.

Add the external-dependency-manager-*.unitypackage to your plugin
project (assuming you are developing a plugin). If you are redistributing
EDM4U with your plugin, you must follow the
import steps in the Getting Started section!
Copy and rename the
SampleDependencies.xml
file into your plugin and add the dependencies your plugin requires.
The XML file just needs to be under an Editor directory and match the
name *Dependencies.xml. For example,
MyPlugin/Editor/MyPluginDependencies.xml.
Follow the steps in the Getting Started
section when you are exporting your plugin package.

For example, to add the Google Play Games library
(com.google.android.gms:play-services-games package) at version 9.8.0 to
the set of a plugin's Android dependencies:

<dependencies>
  <androidPackages>
    <androidPackage spec="com.google.android.gms:play-services-games:9.8.0">
      <androidSdkPackageIds>
        <androidSdkPackageId>extra-google-m2repository</androidSdkPackageId>
      </androidSdkPackageIds>
    </androidPackage>
  </androidPackages>
</dependencies>

The version specification (last component) supports:

Specific versions e.g 9.8.0
Partial matches e.g 9.8.+ would match 9.8.0, 9.8.1 etc. choosing the most
recent version.
Latest version using LATEST or +. We do not recommend using this
unless you're 100% sure the library you depend upon will not break your
Unity plugin in future.

The above example specifies the dependency as a component of the Android SDK
manager such that the Android SDK manager will be executed to install the
package if it's not found. If your Android dependency is located on Maven
central it's possible to specify the package simply using the androidPackage
element:

<dependencies>
  <androidPackages>
    <androidPackage spec="com.google.api-client:google-api-client-android:1.22.0" />
  </androidPackages>
</dependencies>

Auto-resolution

By default the Android Resolver automatically monitors the dependencies you have
specified and the Plugins/Android folder of your Unity project. The
resolution process runs when the specified dependencies are not present in your
project.

The auto-resolution process can be disabled via the
Assets > External Dependency Manager > Android Resolver > Settings menu.

Manual resolution can be performed using the following menu options:

Assets > External Dependency Manager > Android Resolver > Resolve
Assets > External Dependency Manager > Android Resolver > Force Resolve

Deleting libraries

Resolved packages are tracked via asset labels by the Android Resolver.
They can easily be deleted using the
Assets > External Dependency Manager > Android Resolver > Delete Resolved Libraries
menu item.

Android Manifest Variable Processing

Some AAR files (for example play-services-measurement) contain variables that
are processed by the Android Gradle plugin. Unfortunately, Unity does not
perform the same processing when using Unity's Internal Build System, so the
Android Resolver plugin handles known cases of this variable substitution
by exploding the AAR into a folder and replacing ${applicationId} with the
bundleID.

Disabling AAR explosion and therefore Android manifest processing can be done
via the Assets > External Dependency Manager > Android Resolver > Settings
menu. You may want to disable explosion of AARs if you're exporting a project
to be built with Gradle / Android Studio.

ABI Stripping

Some AAR files contain native libraries (.so files) for each ABI supported
by Android. Unfortunately, when targeting a single ABI (e.g x86), Unity does
not strip native libraries for unused ABIs. To strip unused ABIs, the Android
Resolver plugin explodes an AAR into a folder and removes unused ABIs to
reduce the built APK size. Furthermore, if native libraries are not stripped
from an APK (e.g you have a mix of Unity's x86 library and some armeabi-v7a
libraries) Android may attempt to load the wrong library for the current
runtime ABI completely breaking your plugin when targeting some architectures.

AAR explosion and therefore ABI stripping can be disabled via the
Assets > External Dependency Manager > Android Resolver > Settings menu.
You may want to disable explosion of AARs if you're exporting a project to be
built with Gradle / Android Studio.

Resolution Strategies

By default the Android Resolver will use Gradle to download dependencies prior
to integrating them into a Unity project. This works with Unity's internal
build system and Gradle / Android Studio project export.

It's possible to change the resolution strategy via the
Assets > External Dependency Manager > Android Resolver > Settings menu.

Download Artifacts with Gradle

Using the default resolution strategy, the Android resolver executes the
following operations:

Remove the result of previous Android resolutions.
e.g Delete all files and directories labeled with "gpsr" under
Plugins/Android from the project.
Collect the set of Android dependencies (libraries) specified by a
project's *Dependencies.xml files.
Run download_artifacts.gradle with Gradle to resolve conflicts and,
if successful, download the set of resolved Android libraries (AARs, JARs).
Process each AAR / JAR so that it can be used with the currently selected
Unity build system (e.g Internal vs. Gradle, Export vs. No Export).
This involves patching each reference to applicationId in the
AndroidManifest.xml with the project's bundle ID. This means resolution
must be run if the bundle ID is changed again.
Move the processed AARs to Plugins/Android so they will be included when
Unity invokes the Android build.

Integrate into mainTemplate.gradle

Unity 5.6 introduced support for customizing the build.gradle used to build
Unity projects with Gradle. When the Patch mainTemplate.gradle setting is
enabled, rather than downloading artifacts before the build, Android resolution
results in the execution of the following operations:

Remove the result of previous Android resolutions.
e.g Delete all files and directories labeled with "gpsr" under
Plugins/Android from the project and remove sections delimited with
// Android Resolver * Start and // Android Resolver * End lines.
Collect the set of Android dependencies (libraries) specified by a
project's *Dependencies.xml files.
Rename any .srcaar files in the build to .aar and exclude them from
being included directly by Unity in the Android build as
mainTemplate.gradle will be patched to include them instead from their
local maven repositories.
Inject the required Gradle repositories into mainTemplate.gradle at the
line matching the pattern
.*apply plugin: 'com\.android\.(application|library)'.* or the section
starting at the line // Android Resolver Repos Start.
If you want to control the injection point in the file, the section
delimited by the lines // Android Resolver Repos Start and
// Android Resolver Repos End should be placed in the global scope
before the dependencies section.
Inject the required Android dependencies (libraries) into
mainTemplate.gradle at the line matching the pattern ***DEPS*** or
the section starting at the line // Android Resolver Dependencies Start.
If you want to control the injection point in the file, the section
delimited by the lines // Android Resolver Dependencies Start and
// Android Resolver Dependencies End should be placed in the
dependencies section.
Inject the packaging options logic, which excludes architecture specific
libraries based upon the selected build target, into mainTemplate.gradle
at the line matching the pattern android +{ or the section starting at
the line // Android Resolver Exclusions Start.
If you want to control the injection point in the file, the section
delimited by the lines // Android Resolver Exclusions Start and
// Android Resolver Exclusions End should be placed in the global
scope before the android section.

Dependency Tracking

The Android Resolver creates the
ProjectSettings/AndroidResolverDependencies.xml to quickly determine the set
of resolved dependencies in a project. This is used by the auto-resolution
process to only run the expensive resolution process when necessary.

Displaying Dependencies

It's possible to display the set of dependencies the Android Resolver
would download and process in your project via the
Assets > External Dependency Manager > Android Resolver > Display Libraries
menu item.

iOS Resolver Usage

The iOS resolver component of this plugin manages
CocoaPods. A CocoaPods Podfile is generated and
the pod tool is executed as a post build process step to add dependencies
to the Xcode project exported by Unity.

Dependencies for iOS are added by referring to CocoaPods.

Add the external-dependency-manager-*.unitypackage to your plugin
project (assuming you are developing a plugin). If you are redistributing
EDM4U with your plugin, you must follow the
import steps in the Getting Started section!
Copy and rename the
SampleDependencies.xml
file into your plugin and add the dependencies your plugin requires.
The XML file just needs to be under an Editor directory and match the
name *Dependencies.xml. For example,
MyPlugin/Editor/MyPluginDependencies.xml.
Follow the steps in the Getting Started
section when you are exporting your plugin package.

For example, to add the AdMob pod, version 7.0 or greater with bitcode enabled:

<dependencies>
  <iosPods>
    <iosPod name="Google-Mobile-Ads-SDK" version="~> 7.0" bitcodeEnabled="true"
            minTargetSdk="6.0" addToAllTargets="false" />
  </iosPods>
</dependencies>

Integration Strategies

The CocoaPods are either:
* Downloaded and injected into the Xcode project file directly, rather than
creating a separate xcworkspace. We call this Xcode project integration.
* If the Unity version supports opening a xcworkspace file, the pod tool
is used as intended to generate a xcworkspace which references the
CocoaPods. We call this Xcode workspace integration.

The resolution strategy can be changed via the
Assets > External Dependency Manager > iOS Resolver > Settings menu.

Appending text to generated Podfile

In order to modify the generated Podfile you can create a script like this:
```
using System.IO;
public class PostProcessIOS : MonoBehaviour {
[PostProcessBuildAttribute(45)]//must be between 40 and 50 to ensure that it's not overriden by Podfile generation (40) and that it's added before "pod install" (50)
private static void PostProcessBuild_iOS(BuildTarget target, string buildPath)
{
if (target == BuildTarget.iOS)
{

    using (StreamWriter sw = File.AppendText(buildPath + "/Podfile"))
    {
        //in this example I'm adding an app extension
        sw.WriteLine("\ntarget 'NSExtension' do\n  pod 'Firebase/Messaging', '6.6.0'\nend");
    }
}

}
```

Package Manager Resolver Usage

Adding registries to the
Package Manager
(PM) is a manual process. The Package Manager Resolver (PMR) component
of this plugin makes it easy for plugin maintainers to distribute new PM
registry servers and easy for plugin users to manage PM registry servers.

Adding Registries

Add the external-dependency-manager-*.unitypackage to your plugin
project (assuming you are developing a plugin). If you are redistributing
EDM4U with your plugin, you must follow the
import steps in the Getting Started section!
Copy and rename the
SampleRegistries.xml
file into your plugin and add the registries your plugin requires.
The XML file just needs to be under an Editor directory and match the
name *Registries.xml or labeled with gumpr_registries. For example,
MyPlugin/Editor/MyPluginRegistries.xml.
Follow the steps in the Getting Started
section when you are exporting your plugin package.

For example, to add a registry for plugins in the scope com.coolstuff:

<registries>
  <registry name="Cool Stuff"
            url="https://unityregistry.coolstuff.com"
            termsOfService="https://coolstuff.com/unityregistry/terms"
            privacyPolicy="https://coolstuff.com/unityregistry/privacy">
    <scopes>
      <scope>com.coolstuff</scope>
    </scopes>
  </registry>
</registries>

When PMR is loaded it will prompt the developer to add the registry to their
project if it isn't already present in the Packages/manifest.json file.

For more information, see Unity's documentation on
scoped package registries.

Managing Registries

It's possible to add and remove registries that are specified via PMR
XML configuration files via the following menu options:

Assets > External Dependency Manager > Package Manager Resolver > Add Registries will prompt the user with a window which allows them to
add registries discovered in the project to the Package Manager.
Assets > External Dependency Manager > Package Manager Resolver > Remove Registries will prompt the user with a window which allows them to
remove registries discovered in the project from the Package Manager.
Assets > External Dependency Manager > Package Manager Resolver > Modify Registries will prompt the user with a window which allows them to
add or remove registries discovered in the project.

Migration

PMR can migrate Version Handler packages installed in the Assets folder
to PM packages. This requires the plugins to implement the following:

.unitypackage must include a Version Handler manifests that describes
the components of the plugin. If the plugin has no dependencies
the manifest would just include the files in the plugin.
The PM package JSON provided by the registry must include a keyword
(in the versions.VERSION.keyword list) that maps the PM package
to a Version Handler package using the format
vh-name:VERSION_HANDLER_MANIFEST_NAME where VERSION_HANDLER_MANIFEST_NAME
is the name of the manifest defined in the .unitypackage. For
more information see the description of the gvhp_manifestname asset label
in the Version Handler Usage section.

When using the Assets > External Dependency Manager > Package Manager Resolver > Migrate Packages menu option, PMR then
will:

List all Version Handler manager packages in the project.
Search all available packages in the PM registries and fetch keywords
associated with each package parsing the Version Handler manifest names
for each package.
Map each installed Version Handler package to a PM package.
Prompt the user to migrate the discovered packages.
Perform package migration for all selected packages if the user clicks
the Apply button.

Configuration

PMR can be configured via the Assets > External Dependency Manager > Package Manager Resolver > Settings menu option:

Add package registries when enabled, when the plugin loads or registry
configuration files change, this will prompt the user to add registries
that are not present in the Package Manager.
Prompt to add package registries will cause a developer to be prompted
with a window that will ask for confirmation before adding registries.
When this is disabled registries are added silently to the project.
Prompt to migrate packages will cause a developer to be prompted
with a window that will ask for confirmation before migrating packages
installed in the Assets directory to PM packages.
Enable Analytics Reporting when enabled, reports the use of the plugin
to the developers so they can make imrpovements.
Verbose logging when enabled prints debug information to the console
which can be useful when filing bug reports.

Version Handler Usage

The Version Handler component of this plugin manages:

Shared Unity plugin dependencies.
Upgrading Unity plugins by cleaning up old files from previous versions.
Uninstallation of plugins that are distributed with manifest files.
Restoration of plugin assets to their original install locations if assets
are tagged with the exportpath label.

Since the Version Handler needs to modify Unity asset metadata (.meta files),
to enable / disable components, rename and delete asset files it does not
work with Package Manager installed packages. It's still possible to
include EDM4U in Package Manager packages, the Version Handler component
simply won't do anything to PM plugins in this case.

Using Version Handler Managed Plugins

If a plugin is imported at multiple different versions into a project, if
the Version Handler is enabled, it will automatically check all managed
assets to determine the set of assets that are out of date and assets that
should be removed. To disable automatic checking managed assets disable
the Enable version management option in the
Assets > External Dependency Manager > Version Handler > Settings menu.

If version management is disabled, it's possible to check managed assets
manually using the
Assets > External Dependency Manager > Version Handler > Update menu option.

Listing Managed Plugins

Plugins managed by the Version Handler, those that ship with manifest files,
can displayed using the Assets > External Dependency Manager > Version Handler > Display Managed Packages menu option. The list of plugins
are written to the console window along with the set of files used by each
plugin.

Uninstalling Managed Plugins

Plugins managed by the Version Handler, those that ship with manifest files,
can be removed using the Assets > External Dependency Manager > Version Handler > Uninstall Managed Packages menu option. This operation
will display a window that allows a developer to select a set of plugins to
remove which will remove all files owned by each plugin excluding those that
are in use by other installed plugins.

Files managed by the Version Handler, those labeled with the gvh asset label,
can be checked to see whether anything needs to be upgraded, disabled or
removed using the Assets > External Dependency Manager > Version Handler > Update menu option.

Restore Install Paths

Some developers move assets around in their project which can make it
harder for plugin maintainers to debug issues if this breaks Unity's
special folders rules.
If assets are labeled with their original install / export path
(see gvhp_exportpath below), Version Handler can restore assets to their
original locations when using the Assets > External Dependency Manager > Version Handler > Move Files To Install Locations menu option.

Settings

Some behavior of the Version Handler can be configured via the
Assets > External Dependency Manager > Version Handler > Settings menu
option.

Enable version management controls whether the plugin should automatically
check asset versions and apply changes. If this is disabled the process
should be run manually when installing or upgrading managed plugins using
Assets > External Dependency Manager > Version Handler > Update.
Rename to canonical filenames is a legacy option that will rename files to
remove version numbers and other labels from filenames.
Prompt for obsolete file deletion enables the display of a window when
obsolete files are deleted allowing the developer to select which files to
delete and those to keep.
Allow disabling files via renaming controls whether obsolete or disabled
files should be disabled by renaming them to myfilename_DISABLED.
Renaming to disable files is required in some scenarios where Unity doesn't
support removing files from the build via the PluginImporter.
Enable Analytics Reporting enables / disables usage reporting to plugin
developers to improve the product.
Verbose logging enables very noisy log output that is useful for
debugging while filing a bug report or building a new managed plugin.
Use project settings saves settings for the plugin in the project rather
than system-wide.

Redistributing a Managed Plugin

The Version Handler employs a couple of methods for managing version
selection, upgrade and removal of plugins.

Each plugin can ship with a manifest file that lists the files it includes.
This makes it possible for Version Handler to calculate the difference
in assets between the most recent release of a plugin and the previous
release installed in a project. If a files are removed the Version Handler
will prompt the user to clean up obsolete files.
Plugins can ship using assets with unique names, unique GUIDs and version
number labels. Version numbers can be attached to assets using labels or
added to the filename (e.g myfile.txt would be `myfile_version-x.y.z.txt).
This allows the Version Handler to determine which set of files are the
same file at different versions, select the most recent version and prompt
the developer to clean up old versions.

Unity plugins can be managed by the Version Handler using the following steps:

Add the gvh asset label to each asset (file) you want Version Handler
to manage.
Add the gvh_version-VERSION label to each asset where VERSION is the
version of the plugin you're releasing (e.g 1.2.3).
Add the gvhp_exportpath-PATH label to each asset where PATH is the
export path of the file when the .unitypackage is created. This is
used to track files if they're moved around in a project by developers.
Optional: Add gvh_targets-editor label to each editor DLL in your
plugin and disable editor as a target platform for the DLL.
The Version Handler will enable the most recent version of this DLL when
the plugin is imported.
Optional: If your plugin is included in other Unity plugins, you should
add the version number to each filename and change the GUID of each asset.
This allows multiple versions of your plugin to be imported into a Unity
project, with the Version Handler component activating only the most
recent version.
Create a manifest text file named MY_UNIQUE_PLUGIN_NAME_VERSION.txt
that lists all the files in your plugin relative to the project root.
Then add the gvh_manifest label to the asset to indicate this file is
a plugin manifest.
Optional: Add a gvhp_manifestname-NAME label to your manifest file
to provide a human readable name for your package. If this isn't provided
the name of the manifest file will be used as the package name.
NAME can match the pattern [0-9]+[a-zA-Z -]' where a leading integer will set the priority of the name where0` is the highest priority
and preferably used as the display name. The lowest value (i.e highest
priority name) will be used as the display name and all other specified
names will be aliases of the display name. Aliases can refer to previous
names of the package allowing renaming across published versions.
Redistribute EDM4U Unity plugin with your plugin.
See the Plugin Redistribution for the details.

If you follow these steps:

When users import a newer version of your plugin, files referenced by the
older version's manifest are cleaned up.
The latest version of the plugin will be selected when users import
multiple packages that include your plugin, assuming the steps in
Plugin Redistribution are followed.

Building from Source

To build this plugin from source you need the following tools installed:
* Unity (with iOS and Android modules installed)

You can build the plugin by running the following from your shell
(Linux / OSX):

./gradlew build

or Windows:

./gradlew.bat build

Releasing

Each time a new build of this plugin is checked into the source tree you
need to do the following:

Bump the plugin version variable pluginVersion in build.gradle
Update CHANGELOG.md with the new version number and changes included in
the release.
Build the release using ./gradlew release which performs the following:
- Updates external-dependency-manager-*.unitypackage
- Copies the unpacked plugin to the exploded directory.
- Updates template metadata files in the plugin directory.
  The GUIDs of all asset metadata is modified due to the version number
  change. Each file within the plugin is versioned to allow multiple
  versions of the plugin to be imported into a Unity project which allows
  the most recent version to be activated by the Version Handler
  component.
Create release commit using ./gradlew gitCreateReleaseCommit which
performs git commit -a -m "description from CHANGELOG.md"
Once the release commit is merge, tag the release using
./gradlew gitTagRelease which performs the following:
- git tag -a pluginVersion -m "version RELEASE" to tag the release.
Update tags on remote branch using git push --tag REMOTE HEAD:master