New predefined variable: CI_MERGE_REQUEST_URL, CI_COMMIT_URL

Everyone can contribute. Help move this issue forward while earning points, leveling up and collecting rewards.

• Close this issue

We have a lot of variables related to merge requests, like CI_MERGE_REQUEST_PROJECT_URL.

We're lacking the basics: CI_MERGE_REQUEST_URL and CI_COMMIT_URL.

Related commit where ~ 10 MR related environment variables were added: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24595/diffs

CC @ayufan @jlenny @markglenfletcher