Auto-tag alpha images in Git that we can generate full releases from

ci/build.sh

@@ -70,6 +70,21 @@ elif [ -n "$DOCKER_PASSWORD" ] && [ "$TRAVIS_BRANCH" == "master" ] && [ "$TRAVIS
   docker push $DOCKER_TAG:$new_alpha
 else
   echo "Skip Docker pushing"
+  # Major.minor.patch version format
+  latest_release=`wget -q $DOCKER_TAGS -O - | jq -r .[].name | grep -v alpha | grep -v latest | sort --version-sort --field-separator=. | tail -1`
+  latest_major=`echo $latest_release | tr '.' $'\n' | sed -n 1p`
+  latest_minor=`echo $latest_release | tr '.' $'\n' | sed -n 2p`
+  latest_alpha=`wget -q $DOCKER_TAGS -O - | jq -r .[].name | grep alpha | grep "^$latest_major.$latest_minor" | sed 's/-alpha//g' | sort --version-sort --field-separator=. | tail -1`
+  if [ -n "$latest_alpha" ]; then
+    echo "Most recent release version: $latest_release, most recent alpha: $latest_alpha-alpha"
+  else
+    echo "Most recent release version: $latest_release, most recent alpha does not yet exist"
+    latest_alpha="$latest_release"
+  fi
+  new_patch=$((`echo $latest_alpha | tr '.' $'\n' | sed -n 3p`+1))
+  new_alpha="$latest_major.$latest_minor.$new_patch-alpha"
+  echo "Attempting to git tag with version v$new_alpha"
+  git tag "v$new_alpha"
 fi
 
 echo "DONE"