ci: Push release branches for wifi libraries to github

.gitlab-ci.yml

@@ -5,6 +5,7 @@ push_master_to_github:
   stage: deploy
   only:
     - master
+    - /^release\/v/
 #  when: on_success
   image: espressif/esp32-ci-env
   variables:
@@ -18,4 +19,11 @@ push_master_to_github:
     - chmod 600 ~/.ssh/id_rsa
     - echo -e "Host github.com\n\tStrictHostKeyChecking no\n" >> ~/.ssh/config
     - git remote add github [email protected]:espressif/esp32-wifi-lib.git
-    - git push github HEAD:master
+    # What the next line of script does: goes through the list of refs for all branches we push to github,
+    # generates a snippet of shell which is evaluated. The snippet checks CI_BUILD_REF against the SHA
+    # (aka objectname) at tip of each branch, and if any SHAs match then it checks out the local branch
+    # and then pushes that ref to a corresponding github branch
+    #
+    # NB: In gitlab 9.x, CI_BUILD_REF was deprecated. New name is CI_COMMIT_REF. If below command suddenly
+    # generates bash syntax errors, this is probably why.
+    - eval $(git for-each-ref --shell bash --format 'if [ $CI_BUILD_REF == %(objectname) ]; then git checkout -B %(refname:strip=3); git push --follow-tags github %(refname:strip=3); fi;' $GITHUB_PUSH_REFS)