[???] android build: Add suffix to versionName when testing Sentry.

Part of the process of building a Sentry-enabled release involves
uploading the release's source map to sentry.io. Releases are
distinguished only by the "release name", which for Android is the
`versionName`.

[Before being merged, if it ever is, this should be consolidated into
the existing `defaultConfig` block. It is where it is only to simplify
rebasing past a version bump.]

Author: rk-for-zulip

android/app/build.gradle

@@ -129,6 +129,35 @@ android {
         sourceCompatibility JavaVersion.VERSION_1_8
         targetCompatibility JavaVersion.VERSION_1_8
     }
+    defaultConfig {
+        // Marker for unsigned Sentry-enabled builds. Presumably, if you're
+        // making such a build, you're really just testing Sentry and won't want
+        // your development "releases" mixed in with real releases.
+        //
+        // The formatting of this affix is almost entirely arbitrary; it's
+        // intended for humans to read, not machines. Adjust to taste -- but
+        // please leave the username and date in, for the sake of other people
+        // looking at Sentry events.
+        if (project.hasProperty('sentry') && !project.hasProperty('signed')) {
+            // use local git-config email, which is not necessarily `whoami`
+            def username = ({ ->
+                def proc = "git config --get user.email".execute()
+                proc.waitFor()
+                proc.in.text.takeWhile { it != '@'}
+            })()
+            if (username.isEmpty()) {
+                throw new GradleException("Git user.email not configured?")
+            }
+
+            def date = new Date().format('yyyy-MM-dd')
+
+            // Increment manually as desired. (Or replace with text, if you
+            // prefer.)
+            def revision = "001"
+
+            versionName += "-${username}-${date}.${revision}"
+        }
+    }
     signingConfigs {
         release {
             if (project.hasProperty('signed')) {