auto publish sbt plugin from GitHub Actions


This is a GitHub Actions version of auto publish sbt plugin from Travis CI.

In this post, we'll try to automate the release of an sbt plugin using Ólaf's olafurpg/sbt-ci-release. The README of sbt-ci-release covers the use case for a library published to Sonatype OSS. Read it thoroughly since this post will skip over the details that do not change for publishing sbt plugins.

Automated release in general is a best practice, but there's one benefit specifically for sbt plugin releases. Using this setup allows multiple people to share the authorization to release an sbt plugin without adding them to Bintray sbt organization. This is useful for plugins maintained at work.

step 1: sbt-ci-release

Remove sbt-release if you're using that. Add sbt-ci-release instead.

addSbtPlugin("org.foundweekends" %% "sbt-bintray" % "0.6.1")
addSbtPlugin("com.geirsson" % "sbt-ci-release" % "1.5.4")
addSbtPlugin("com.jsuereth" % "sbt-pgp" % "2.1.1") // for gpg 2

Don't forget to remove version.sbt.

step 2: -SNAPSHOT version

We need to also suppress sbt-dynver a little bit so we get a simpler -SNAPSHOT versions for commits that are not tagged:

ThisBuild / dynverSonatypeSnapshots := true
ThisBuild / version := {
  val orig = (ThisBuild / version).value
  if (orig.endsWith("-SNAPSHOT")) "2.2.0-SNAPSHOT"
  else orig

step 3: recover sbt-bintray settings

We typically use sbt-bintray to publish plugins, so rewire publishTo back to bintray / publishTo. Also set publishMavenStyle to false.

  publishMavenStyle := false,
  bintrayOrganization := Some("sbt"),
  bintrayRepository := "sbt-plugin-releases",
  publishTo := (bintray / publishTo).value,

step 4: remove bintrayReleaseOnPublish overrides

We need to release on publish, so if you have bintrayReleaseOnPublish := false, in your build.sbt remove it.

// bintrayReleaseOnPublish := false,

step 5: create a fresh GPG key

Follow the instruction in olafurpg/sbt-ci-release to generate a fresh GPG key.

$ gpg --gen-key
gpg (GnuPG/MacGPG2) 2.2.20; Copyright (C) 2020 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Note: Use "gpg --full-generate-key" for a full featured key generation dialog.
GnuPG needs to construct a user ID to identify your key.
Real name: sbt-avro bot
Email address:
public and secret key created and signed.
pub   rsa2048 2020-08-07 [SC] [expires: 2022-08-07]
uid                      sbt-avro bot <>
sub   rsa2048 2020-08-07 [E] [expires: 2022-08-07]

Take this down as LONG_ID:

echo $LONG_ID
gpg --armor --export $LONG_ID

Submit the public key to

step 6: Secrets

Set up secrets from<owner>/<repo>/settings/secrets/actions:

  • BINTRAY_USER: Bintray user name.
  • BINTRAY_PASS: The API key for the Bintray user.
  • PGP_PASSPHRASE: The randomly generated password you used to create a fresh
    GPG key. If the password contains bash special characters, make sure to
    escape it by wrapping it in single quotes 'my?pa$$word', see
    Travis Environment Variables.
  • PGP_SECRET: The base64 encoding of your private key that you can
    export from the command line like here below
# macOS
gpg --armor --export-secret-keys $LONG_ID | base64 | pbcopy
# Ubuntu (assuming GNU base64)
gpg --armor --export-secret-keys $LONG_ID | base64 -w0 | xclip
# Arch
gpg --armor --export-secret-keys $LONG_ID | base64 | sed -z 's;\n;;g' | xclip -selection clipboard -i
# FreeBSD (assuming BSD base64)
gpg --armor --export-secret-keys $LONG_ID | base64 | xclip

step 7: Decode the secret key

For gpg 2.2 that are on more recent Ubuntu distros, we need to hand decode the private keys ourselves for now. Add .github/

echo $PGP_SECRET | base64 --decode | gpg  --batch --import

And give it execution rights:

$ chmod +x .github/

step 8: GitHub Actions YAML

Create .github/workflows/ci.yml. See Setting up GitHub Actions with sbt for details:

name: CI
  # 2am EST every Saturday
  - cron: '0 7 * * 6'
    runs-on: ubuntu-latest
      # define Java options for both official sbt and sbt-extras
      JAVA_OPTS: -Xms2048M -Xmx2048M -Xss6M -XX:ReservedCodeCacheSize=256M -Dfile.encoding=UTF-8
      JVM_OPTS:  -Xms2048M -Xmx2048M -Xss6M -XX:ReservedCodeCacheSize=256M -Dfile.encoding=UTF-8
    - name: Checkout
      uses: actions/checkout@v2
    - name: Setup Scala
      uses: olafurpg/setup-scala@v10
        java-version: "adopt@1.8"
    - name: Coursier cache
      uses: coursier/cache-action@v5
    - name: Build and test
      run: |
        sbt -v clean scalafmtCheckAll test scripted
        rm -rf "$HOME/.ivy2/local" || true
        find $HOME/Library/Caches/Coursier/v1        -name "ivydata-*.properties" -delete || true
        find $HOME/.ivy2/cache                       -name "ivydata-*.properties" -delete || true
        find $HOME/.cache/coursier/v1                -name "ivydata-*.properties" -delete || true
        find $HOME/.sbt

Create .github/worflows/release.yml for releasing:

name: Release
      - '*'
    runs-on: ubuntu-latest
      # define Java options for both official sbt and sbt-extras
      JAVA_OPTS: -Xms2048M -Xmx2048M -Xss6M -XX:ReservedCodeCacheSize=256M -Dfile.encoding=UTF-8
      JVM_OPTS:  -Xms2048M -Xmx2048M -Xss6M -XX:ReservedCodeCacheSize=256M -Dfile.encoding=UTF-8
    - name: Checkout
      uses: actions/checkout@v2
    - name: Setup Scala
      uses: olafurpg/setup-scala@v10
        java-version: "adopt@1.8"
    - name: Coursier cache
      uses: coursier/cache-action@v5
    - name: Test
      run: |
        sbt test packagedArtifacts
    - name: Release
        BINTRAY_USER: ${{ secrets.BINTRAY_USER }}
        BINTRAY_PASS: ${{ secrets.BINTRAY_PASS }}
        PGP_PASSPHRASE: ${{ secrets.PGP_PASSPHRASE }}
        PGP_SECRET: ${{ secrets.PGP_SECRET }}
        CI_CLEAN: clean
        CI_RELEASE: publishSigned
        CI_SONATYPE_RELEASE: version
      run: |
        sbt ci-release

For cross-built plugins, adjust the above commands accordingly.

step 9: tag-based release

When you're ready to publish your plugin, tag the commit and push it.

git tag -a v0.1.0 -m "v0.1.0"
git push origin v0.1.0

This should start a release job on GitHub Actions.

notes about gpg 2

sbt-pgp uses gpg's --passphrase option during signing. According to the documentation:

Note that since Version 2.0 this passphrase is only used if the option --batch has also been given. Since Version 2.1 the --pinentry-mode also needs to be set to loopback.

sbt-pgp 2.1.1 was released with version detection of gpg command, which will add the necessary --pinetry-mode loopback options.

sbt-ci-release uses --import, which also now fails silently on gpg 2.2 and causes

gpg: key 24A4616356F15CE1: public key "sbt-something bot <>" imported
gpg: key 24A4616356F15CE1/24A4616356F15CE1: error sending to agent: Inappropriate ioctl for device
gpg: error building skey array: Inappropriate ioctl for device
gpg: Total number processed: 1
gpg:               imported: 1
gpg:       secret keys read: 1
Tag push detected, publishing a stable release
[info] gpg: no default secret key: No secret key
[info] gpg: signing failed: No secret key
[error] java.lang.RuntimeException: Failure running 'gpg --batch --pinentry-mode loopback --passphrase *** --detach-sign --armor --use-agent --output /home/runner/work/sbt-projectmatrix/sbt-projectmatrix/target/scala-2.12/sbt-1.0/sbt-projectmatrix-0.7.1-M1.jar.asc /home/runner/work/sbt-projectmatrix/sbt-projectmatrix/target/scala-2.12/sbt-1.0/sbt-projectmatrix-0.7.1-M1.jar'.  Exit code: 2

According to T2313, the workaround for this is to use --batch --import, which our .github/ will do.

I was peripherally aware of some of this issue, but never took action since Xenial image that I've been using came with gpg 1.4 which is incompatible with these new options. Since GitHub Actions uses Bionic, and soon to move to Focal we're seeing this more often.