A few environment vars are undocumented

[gittycat]

I've noticed that many of the environment variables listed when doing a buildkite-agent start --help are not documented here: https://buildkite.com/docs/guides/environment-variables, although the ones I've tried can be queried in the build step.
A useful one is BUILDKITE_BUILD_PATH

BUILDKITE_AGENT_CONFIG
BUILDKITE_AGENT_DEBUG
BUILDKITE_AGENT_DEBUG_HTTP
BUILDKITE_AGENT_ENDPOINT
BUILDKITE_AGENT_META_DATA
BUILDKITE_AGENT_NO_COLOR
BUILDKITE_AGENT_PRIORITY
BUILDKITE_AGENT_TOKEN
BUILDKITE_BOOTSTRAP_SCRIPT_PATH
BUILDKITE_BUILD_PATH
BUILDKITE_HOOKS_PATH
BUILDKITE_NO_AUTOMATIC_SSH_FINGERPRINT_VERIFICATION
BUILDKITE_NO_COMMAND_EVAL
BUILDKITE_NO_PTY

[toolmantim]

Hey, thanks for the heads up. Some of these are designed to help the agent communicate with the bootstrap.sh script, but we should probably document them in a different section of the doc (as long as they're not internal / expected to change).

[gittycat]

Yes, you could do a review of what buildkite-agent start --help puts out and decide on what you want to have public. I personally had a need to figure out the relative path from $BUILDKITE_BUILD_PATH where the repo src code is located. I ended up using this

SRC=`pwd | sed 's|'$BUILDKITE_BUILD_PATH'/'$BUILDKITE_AGENT_NAME'/||'`

[harrietgrace]

Hey @gittycat! 👋🏻It took us a while, but we've finally done a big update to the env vars doc 😄There was also a recent agent update that cleaned up a bunch of the vars it was displaying too, so everything should be covered now.