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`nextflow.scm`

The nextflow.scm package defines the Git provider interface and implements several built-in Git providers. It also manages local pipeline repositories using a Strategy pattern to support different repository management approaches.

Class Diagram

        classDiagram
    %%
    %% nextflow.scm
    %%
    direction LR

    CmdRun --> AssetManager : run

    class AssetManager {
        project : String
        mainScript : String
        provider : RepositoryProvider
        strategy : RepositoryStrategy
        hub : String
        providerConfigs : List~ProviderConfig~
    }

    class RepositoryStrategyType {
        <<enumeration>>
        LEGACY
        MULTI_REVISION
    }

    AssetManager --> RepositoryStrategyType
    AssetManager "1" --o "1" RepositoryStrategy
    AssetManager "1" --o "1" RepositoryProvider
    AssetManager "1" --* "*" ProviderConfig

    class RepositoryStrategy {
        <<interface>>
    }
    class AbstractRepositoryStrategy {
        <<abstract>>
        project : String
        provider : RepositoryProvider
        root : File
    }
    class LegacyRepositoryStrategy {
        localPath : File
    }
    class MultiRevisionRepositoryStrategy {
        revision : String
        bareRepo : File
        commitPath : File
        revisionSubdir : File
    }

    RepositoryStrategy <|-- AbstractRepositoryStrategy
    AbstractRepositoryStrategy <|-- LegacyRepositoryStrategy
    AbstractRepositoryStrategy <|-- MultiRevisionRepositoryStrategy

    class RepositoryProvider {
        <<abstract>>
    }

    RepositoryStrategy --> RepositoryProvider

    RepositoryProvider <|-- AzureRepositoryProvider
    RepositoryProvider <|-- BitbucketRepositoryProvider
    RepositoryProvider <|-- BitbucketServerRepositoryProvider
    RepositoryProvider <|-- GiteaRepositoryProvider
    RepositoryProvider <|-- GithubRepositoryProvider
    RepositoryProvider <|-- GitlabRepositoryProvider
    RepositoryProvider <|-- LocalRepositoryProvider

Note

Some classes may be excluded from the above diagram for brevity.

Architecture overview

Repository strategies

The AssetManager uses the Strategy pattern to support different ways of managing local pipeline installations:

LegacyRepositoryStrategy: Traditional approach where each project gets a full git clone in $NXF_HOME/{project} directory. Only one revision can exist at a time per project.
MultiRevisionRepositoryStrategy: Modern approach that allows multiple revisions to coexist efficiently by:
- Maintaining a shared bare repository in $NXF_HOME/.repos/{project}/bare/
- Creating lightweight clones for each commit in $NXF_HOME/.repos/{project}/clones/{commitId}/
- Sharing git objects between revisions to minimize disk space

Strategy selection

The AssetManager automatically selects the appropriate strategy based on:

Environment variable: NXF_SCM_LEGACY=true forces legacy mode
Repository status: Detected by checking existing repository structure:
- UNINITIALIZED: No repository exists, use Multi-Revision (default)
- LEGACY_ONLY: Only legacy .git directory exists, use Legacy
- BARE_ONLY: Only bare repository exists, use Multi-Revision
- HYBRID: Both exist, prefer Multi-Revision

Repository provider

The RepositoryProvider class is the base class for all Git providers. It defines how to authenticate with the provider, clone a Git repository, inspect branches and tags, etc. The provider is used by repository strategies to interact with remote Git services.

Key components

AssetManager

Central class that manages pipeline assets. Key responsibilities include:

Project name resolution and validation
Strategy selection and initialization
Provider configuration and authentication
Repository download and checkout operations
Coordination between strategy and provider

RepositoryStrategy

Interface defining for repository management operations:

download(): Download or update a revision
checkout(): Switch to a specific revision
drop(): Delete local copies
getLocalPath(): Get path to working directory
getGit(): Access JGit repository instance

nextflow.scm