LibVCS4j

LibVCS4j is a Java programming library for repository mining with a common API for different version control systems and issue trackers. The library integrates existing software (e.g. JGit) to access repository routines, adds additional features for data analysis, and, ultimately, makes subsequent analysis tools independent from particular repository systems.

	Package	Javadoc	Description	License
API			Defines the common data model.	MIT
Implementation			Implemenations the API.	GNU GPLv3
Tools			Additional tools.	GNU LGPLv3

Quickstart

The following listing demonstrates how to iterate through the history of a Git repository:

VCSEngine vcs = VCSEngineBuilder
    .ofGit("https://github.com/amaembo/streamex.git")
    .build();

for (RevisionRange range : vcs) {
    range.getAddedFiles();
    range.getRemovedFiles();
    range.getModifiedFiles();
    range.getRelocatedFiles();
    ...
}

You can also process a specific subdirectory and branch:

VCSEngine vcs = VCSEngineBuilder
    .ofGit("https://github.com/amaembo/streamex.git")
    .withRoot("src/main")
    .withBranch("multirelease")
    .build();

In order to extract issues referenced in commit messages, you need to assign an ITEngine:

ITEngine it = ITEngineBuilder
    .ofGithub("https://github.com/amaembo/streamex")
    .build();

VCSEngine vcs = ...
vcs.setITEngine(it);

for (RevisionRange range : vcs) {
    // Returns an empty list if no ITEngine is assigned to `vcs`.
    range.getLatestCommit().getIssues();
    ...
}

While processing a repository, LibVCS4j not only generates metadata such as file change information, but also allows to access the files of the currently checked out revision:

VCSEngine vcs = ...

for (RevisionRange range : vcs) {
    // Path to the root of the currently checked out revivion.
    range.getRevision().getOutput();

    // Returns the files of the currenlty checked out revision as list.
    range.getRevision().getFiles();
}

If required, the target directory (i.e. the SVN working copy or the Git/Mercurial clone directory) can be configured as follows:

VCSEngine vcs = VCSEngineBuilder
    .ofGit("https://github.com/amaembo/streamex.git")
    .withTarget("path/to/clone/directory")
    .build();

If no target directory is specified, a temporary directory is created (and deleted using a shutdown hook).

Project Structure

The library is divided into an API and implementation, as well as further submodules that are supposed to provide additional features (e.g. aggregation of different metrics). The API has no external dependencies and defines a common data model that allows to decouple analysis tools from particular repository systems. The implementation, on the other hand, provides the actual version control system engines (GitEngine, HGEngine, SVNEngine, SingleEngine), issue tracker engines (GithubEngine, GitlabEngine), and engine builder (VCSEngineBuilder and ITEngineBuilder).

Data Model

The following UML diagram depicts the data model defined by the API submodule. For the sake of clarity, the modifier of the attributes and methods are not shown since they are public anyway (in fact attributes are not public, but can be accessed with corresponding getter methods which, in turn, are public). Furthermore, all attributes are readonly.

Supported Repositories

Version Control Systems

The following version control systems (and protocols) are supported:

• Git: file://, http(s)://, ssh://, git@
• Mercurial: file://, http(s)://, ssh://
• Subversion: file://, http(s)://, svn://, svn+ssh://

The VCSEngineBuilder, for the sake of convenience, automatically maps regular file paths to the file:// protocol. For example, a local Mercurial repository may be configured with:

// The path is mapped to 'file:///path/to/repository'.
VCSEngineBuilder.ofHG("/path/to/repository")

There is a special engine called SingleEngine. It is used to process a local directory or file. When using this engine, a single revision is generated with all files being reported as added.

Issue Tracker

The following issue tracker (and authentication mechanisms) are supported:

• Github: anonymous, username/password, token
• Gitlab: token

Note that, due to the server limitations of some providers, extracting issues from an issue tracker may noticeably slow down an analysis (1 -- 2 seconds per request). Hence, it is recommended to enable this feature only if required (see Quickstart). Also, some providers permit only a certain number of requests per day. If exceeded, subsequent requests are ignored.

Installation

Releases are available at Maven Central.