Add OpenUPM support

This commit modifies the build.gradle file so that it explodes the generated UPM package into the repo as part of the release process.

Author: f1yingbanana

build.gradle

@@ -264,14 +264,18 @@ project.ext {
   pluginStagingAreaDir = new File(buildDir, "staging")
   // Directory where the build plugin is unpacked to.
   pluginExplodedDir = new File(scriptDirectory, "exploded")
+  // Directory where the UPM package is unpacked to.
+  pluginUpmDir = new File(scriptDirectory, "upm")
   // Base filename of the released plugin.
   currentPluginBasename = "external-dependency-manager"
+  // Base UPM package name of the released plugin.
+  currentPluginUpmPackageName = "com.google.external-dependency-manager"
   // Where the exported plugin file is built before it's copied to the release
   // location.
   pluginExportFile = new File(buildDir, currentPluginBasename + ".unitypackage")
   // Where the exported UPM plugin file is built.
   pluginUpmExportFile = new File(buildDir,
-                                 currentPluginBasename + pluginVersion + ".tgz")
+                                 currentPluginUpmPackageName + "-" + pluginVersion + ".tgz")
   // Directory within the plugin staging area that just contains the plugin.
   pluginAssetsDir = new File("Assets", "ExternalDependencyManager")
   // Directories within the staging area to export.
@@ -2069,8 +2073,7 @@ buildPlugin.with {
 }
 
 // Guid paths for UPM package.
-File upmPluginPackageDir = new File("com.google.external-dependency-manager",
-    "ExternalDependencyManager")
+File upmPluginPackageDir = new File(currentPluginUpmPackageName, "ExternalDependencyManager")
 File upmPluginEditorDir = new File(upmPluginPackageDir, "Editor")
 File upmPluginDllDir = new File(upmPluginEditorDir, project.ext.pluginVersion)
 
@@ -2142,6 +2145,15 @@ task releasePlugin(dependsOn: [buildPlugin, buildUpmPlugin]) {
         it.path + "/**/*"
       }
     }
+    delete fileTree(dir: project.ext.pluginUpmDir) 
+    copy {
+      // Rename the top-level package folder to upm.
+      eachFile {
+        path = path.replaceFirst(/^.+?\//, "upm/")
+      }  
+      from tarTree(project.ext.pluginUpmExportFile)
+      into project.ext.scriptDirectory
+    }
     pluginTemplateFilesMap.each {
       sourceFile, targetFile -> copyFile(sourceFile, targetFile)
     }