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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​

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:

  1. Environment variable: NXF_SCM_LEGACY=true forces legacy mode
  2. 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
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