'git branch --contains' on CircleCI shows a branch that doesn't have the commit

Build Environment
1

I want to trigger a build only if a tag refers to a commit contained in master.

Fir this purpose, I have a run step that executes:

if ! git branch --contains $CIRCLE_TAG | grep master > /dev/null; then exit 1; fi

I’m doing this because it’s not possible to make it work solely with CircleCI filters (branches and tags).

Problem is:

It works fine locally for a tag that’s not in master, but when I run it on CircleCI, the contains command is listing master.

I logged the result of git branch --contains $CIRCLE_TAG on CircleCI, and it prints out this:

* (HEAD detached at 0.5.5)
master

I ran the pipeline in macos and docker:stable-git executors, and the results were the same.

Could this be a bug, or am I missing something?

config.yml I’m using for the tests:

version: 2.1

add_filters: &add_filters
  filters:
    branches:
      ignore: /.*/
    tags:
      only: /.*/

jobs:
  check_branch:
    docker:
      - image: docker:stable-git
    environment:
      TERM: xterm-256color
    steps:
      - checkout
      - run: |
          if ! git branch --contains $CIRCLE_TAG | grep master > /dev/null; then exit 1; fi

workflows:
  version: 2.1
  release_pod:
    jobs:
      - check_branch:
          <<: *add_filters