ci: add ability to create draft GitHub releases

This adds a `Publish` stage to the combined `Jenkinsfile` which when the
`PUBLISH` parameters is true pushes a __draft__ release to GitHub.
The job remembers the last value of `PUBLISH` parameter selected.

The release uses the contents of the `VERSION` file at the root of the
repo as the name for the release, and leaves the contents to be filled
in by whoever will approve the release.

The automation overwrites - or to be exact, deletes and recreates - the
release, so releated builds for the same release will simply re-create
it. All the built artifacts are included in the release.

Signed-off-by: Jakub Sokołowski <jakub@status.im>

VERSION

@@ -1 +1 @@
-beta.8
+0.1.0-beta.9

ci/Jenkinsfile.combined

@@ -1,4 +1,4 @@
-library 'status-react-jenkins@v1.2.11'
+library 'status-jenkins-lib@v1.2.12'
 
 pipeline {
   agent { label 'linux' }
@@ -16,6 +16,14 @@ pipeline {
     ))
   }
 
+  parameters {
+    booleanParam(
+      name: 'PUBLISH',
+      description: 'Trigger publishing of build results to GitHub.',
+      defaultValue: getPublishDefault(params.PUBLISH),
+    )
+  }
+
   stages {
     stage('Build') {
       parallel {
@@ -59,5 +67,21 @@ pipeline {
         jenkins.setBuildDesc(urls)
       } }
     }
+    stage('Publish') {
+      when { expression { params.PUBLISH } }
+      steps { script {
+        github.publishReleaseFiles(repo: 'status-desktop');
+      } }
+    }
   }
 }
+
+/* Helper that makes PUBLISH default to 'false' unless:
+ * - The build is for a release branch
+ * - A user explicitly specified a value
+ * Since release builds create and re-create GitHub drafts every time. */
+def Boolean getPublishDefault(Boolean previousValue) {
+  if (env.JOB_NAME.startsWith('status-desktop/release')) { return true }
+  if (previousValue != null) { return previousValue }
+  return false
+}

ci/Jenkinsfile.linux

@@ -1,4 +1,4 @@
-library 'status-react-jenkins@v1.2.11'
+library 'status-jenkins-lib@v1.2.12'
 
 pipeline {
   agent {

ci/Jenkinsfile.macos

@@ -1,4 +1,4 @@
-library 'status-react-jenkins@v1.2.11'
+library 'status-jenkins-lib@v1.2.12'
 
 pipeline {
   agent {

ci/Jenkinsfile.windows

@@ -1,4 +1,4 @@
-library 'status-react-jenkins@v1.2.11'
+library 'status-jenkins-lib@v1.2.12'
 
 pipeline {
   agent { label 'windows' }