# Multiple Pipelines

With V2, Nix GitLab CI can generate different pipelines, depending on the
pipeline source (`$CI_PIPELINE_SOURCE`).

By default, no matter which source, the `default` pipeline is built and ran.
`$NIX_CI_PIPELINE` can override that, eg. when manually triggering a run.
To configure which source should be 1-to-1 translated to a pipeline with the
same name, set `$NIX_CI_DEFAULT_SOURCES` to a regex which explicitly does not
match these sources. Or set it to an impossible to match regex, then it will
always run the pipeline named after `$CI_PIPELINE_SOURCE`.

## Example 1: always run default

If you only have a single pipeline, you just have to call it `default`.
Everything else works out of the box.

## Example 2: default and merge_request_event

If you want the source `merge_request_event` to trigger a different pipeline,
name it like that and set `$NIX_CI_DEFAULT_SOURCES` to `^(merge_request_event)$`.
Now a merge request will run this pipeline, while everything else runs `default`.

## Example 3: default, push and web

Set `$NIX_CI_DEFAULT_SOURCES` to `^(push|web)$`.

## Example 4: always run the specific pipelines, never default

Set `$NIX_CI_DEFAULT_SOURCES` to any regex that never matches the sources,
like `a\A` or `nothing`.