fix lint job vs google-services.json-example

 - Now that we migrated to `git-crypt`, the `WooCommerce/google-services.json` file _always_ exists in the repo (albeit encrypted if the repo was not git-crypt-unlocked after being cloned), the logic to decide when to copy the `google-services.json-example` file had to be adjusted
 - Also updated the `README.md` accordingly—to suggest external contributors to copy the example file

Author: AliSoftware

README.md

@@ -41,10 +41,11 @@
 1. If you are a developer at Automattic:
    1. Make sure you have `git-crypt` installed (`brew install git-crypt`)
    1. Search for "WooCommerce Android git-crypt encryption key" in our Secret Store, and copy the Base64 value in your clipboard
-   1. Run `git-crypt unlock <(pbpaste | base64 -d)` to decrypt the encrypted files (including `secrets.properties`)
+   1. Run `git-crypt unlock <(pbpaste | base64 -d)` to decrypt the encrypted files (including `secrets.properties` and `WooCommerce/google-services.json`)
 1. If you are an external contributor:
    1. Generate developer OAuth2 tokens. See the [OAuth2 Authentication](docs/project-overview.md#oauth2-authentication) section for details.
    1. Edit `defaults.properties` and adjust the values as needed—especiallyincluding `wp.oauth.*` ones. See the [Configuration Files](docs/project-overview.md#configuration-files) section for a breakdown of the properties.
+   1. `cp WooCommerce/google-services.json-example WooCommerce/google-services.json` (to replace that encrypted file with placeholder content)
 1. In Android Studio, open the project from the local repository. This will auto-generate `local.properties` with the SDK location.
 1. Optional: Go to Tools → Device Manager and create an emulated device.
 1. Run. (Creates a default virtual device if you skipped the previous step)

WooCommerce/build.gradle

@@ -496,12 +496,13 @@ android.buildTypes.all { buildType ->
     }
 
     // If Google services file doesn't exist, copy example file.
-    if (!file("google-services.json").exists()) {
+    def googleServicesFile = file("google-services.json")
+    if (!googleServicesFile.exists() || isFileEncrypted(googleServicesFile)) {
         tasks.copyGoogleServicesExampleFile.copy()
     }
 
     // Print warning message if example Google services file is used.
-    if ((file("google-services.json").text) == (file("google-services.json-example").text)) {
+    if ((googleServicesFile.text) == (file("google-services.json-example").text)) {
         println("WARNING: You're using the example google-services.json file. Google login will fail.")
     }
 }
@@ -514,6 +515,13 @@ static def loadPropertiesFromFile(inputFile) {
     return properties
 }
 
+static def isFileEncrypted(File file) {
+    def gitcryptHeader = [0x00, 0x47, 0x49, 0x54, 0x43, 0x52, 0x59, 0x50, 0x54] as byte[] // GITCRYPT header
+    def header = new byte[gitcryptHeader.length]
+    file.withInputStream { stream -> stream.read(header) }
+    return Arrays.equals(header, gitcryptHeader)
+}
+
 def isLeakCanaryEnabled() {
     return developerProperties.get("enable_leak_canary") ?: true
 }