git-mirrors: set BUILDKITE_REPO_MIRROR=/path/to/mirror/repo

[pda]

When git-mirrors (currently an experiment) is enabled, export a BUILDKITE_REPO_MIRROR=/path/to/mirror/repo environment variable. This makes it easy to mount the mirror as a volume in docker containers, so that git within the container can access the git reference repository data.

The name BUILDKITE_REPO_MIRROR was chosen to reflect the existing BUILDKITE_REPO environment variable.

This environment variable enables transparent support for git-mirrors in our docker plugin and our docker-compose plugin:

• Support buildkite-agent's git-mirrors; mount BUILDKITE_GIT_MIRROR_PATH. buildkite-plugins/docker-buildkite-plugin#167
• Support buildkite-agent's git-mirrors; mount BUILDKITE_GIT_MIRROR_PATH buildkite-plugins/docker-compose-buildkite-plugin#287

[pda]

Here's a before (current agent master branch) and after (this PR) running a build that does a git log using docker#0c53b57a02e35024b8f55c5bdfab3b4453ef63e3 plugin from buildkite-plugins/docker-buildkite-plugin#167

… seems good.

Here's the pipeline I tested:

env:
  GREETING: hello world

steps:
  - command: "git --no-pager log"
    plugins:
      - docker#0c53b57a02e35024b8f55c5bdfab3b4453ef63e3:
          image: "golang:1.15"
    retry:
      manual:
        permit_on_passed: true

[jayco]

Looks legit! 👌

[chrislloyd]

Thank you! Literally just ran into this issue.