# Building and pushing a container to a registry with environment/git commit tag

One way to implement promotions in GitOps is to have the operator deploy images published with a prefixed environment tag. For example, if you want your operator in your staging cluster to deploy only images ready for staging, you can configure it to watch for images published with the tag `stg-[commit id]`.

Regardless of GitOps, this is quick guide on how to publish an image to a container registry using a combination of a environment/git commit tag. We will be using Azure DevOps.

First, define a variable with a service connection to a container registry. While you’re at it, also define the name of your image.

    variables: 
      Registry.ServiceConnnection: [the name of your service connection]
      ImageName: [the name of your container image]
    

Then, you want to use the `Docker@2` task to build and push and tag all at the same time. It’s nice and easy this way.

    - task: Docker@2
      displayName: Build and Push
      inputs:
        command: buildAndPush
        containerRegistry: $(Registry.ServiceConnnection)
        repository: $(ImageName)
        buildContext: .
        Dockerfile: Dockerfile
        tags: |
          $(DockerTag)
          latest
    

Now the next trick is to have a variable that changes value by stage. You could add a stage per environment (e.g. stage, prod).

Stages support variable definitions as well, so it’s just a matter of defining variables at the stage level. This will let you have distinct values based on the environment.

Using this approach, define a `DockerTag` variable that is composed of another `Environment` variable and a pre-defined pipeline variable for the Git Commit Id.

    variables: 
      Environment: stg
      DockerTag: "$(Environment)-$(Build.SourceVersion)"
    

So, putting it all together, looks like this:

    variables: 
      Registry.ServiceConnnection: [the name of your service connection]
      ImageName: [the name of your container image]
    
    stages:
    - stage: build
      displayName: Build and Push
      variables: 
        Environment: stg
        DockerTag: "$(Environment)-$(Build.SourceVersion)"
      jobs:  
      - job: job_build
        displayName: Build and Push
        pool:
          vmImage: 'ubuntu-latest'
        steps:
        - task: Docker@2
          displayName: Build and Push
          inputs:
            command: buildAndPush
            containerRegistry: $(Registry.ServiceConnnection)
            repository: $(ImageName)
            buildContext: .
            Dockerfile: Dockerfile
            tags: |
              $(DockerTag)
              latest
    

That’s it!