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Git Client Plugin

Introduction

Jenkins and Git

The git client plugin provides git application programming interfaces (APIs) for Jenkins plugins. It can fetch, checkout, branch, list, merge, and tag repositories. Refer to the API documentation for specific API details.

The GitClient interface provides the primary entry points for git access. It supports username / password credentials for git repository access with HTTP and HTTPS protocols (for example, https://github.com/jenkinsci/git-client-plugin or https://git.example.com/your-repo.git ). It supports private key credentials for git repository access with SSH protocol (for example, git@github.com:jenkinsci/git-client-plugin.git or ssh://git@github.com/jenkinsci/git-client-plugin.git ). Credential support is provided by the Jenkins credentials plugin.

Implementations

The git client plugin default implementation requires that command line git is installed on the controller and on every agent that will use git. Command line git implementations working with large files should also install git LFS. The command line git implementation is the canonical implementation of the git interfaces provided by the git client plugin.

Command line git is enabled by default when the git client plugin is installed.

JGit

The git client plugin also includes two optional implementations ("jgit" and "jgitapache") that use Eclipse JGit, a pure Java implementation of git. The JGit implementation in the git client plugin provides most of the functionality of the command line git implementation. When the JGit implementation is incomplete, the gap is noted in console logs.

JGit is disabled by default when the git client plugin is installed.

Enabling JGit

Click the "Add Git" button in the "Tools" section under "Manage Jenkins" to add JGit or JGit with Apache HTTP Client as a git implementation.

Enable JGit or JGit with Apache HTTP Client

JGit timeout

The command line git implementation in the git client plugin provides a timeout setting for many operations like fetch and checkout. Operations that take more than the specified time are canceled. When the timeout is exceeded, the command line git process fails and the git client plugin API operation fails.

The JGit implementation in the git client plugin uses a different concept of timeout. The JGit timeout is a network level transport timeout rather than a timeout of a higher level JGit operation. If the JGit network transport does not receive a response within the defined timeout, the JGit API call fails. The JGit javadoc describes the JGit API.

The JGit timeout implementation prevents JGit operations from hanging indefinitely when a remote server stops responding. It does not stop a JGit operation if it has executed for more than a specified time. The JGit timeout counter is reset each time a response is received from the remote server during the JGit API call. The command line git timeout counter is set at the start of the command line git call and is not reset during the call.

JGit with Apache HTTP Client

The original JGit implementation inside the git client plugin had issues with active directory authentication. A workaround was implemented to provide JGit but use Apache HTTP client for authentication. The issue in JGit has now been resolved and delivered in git client plugin releases. JGit with Apache HTTP Client continues to delivered to assure compatibility.

Installing MinGit for Windows Automatically

Jenkins can install MinGit for Windows automatically. MinGit for Windows is an intentionally minimal, non-interactive distribution of Git for Windows, with third-party applications as its intended audience. Jenkins is well suited to use MinGit on Windows agents.

Configure MinGit for Windows to install automatically

  • Configure a global git tool from "Manage Jenkins" >> "Tools" with git as the Path to Git executable

  • Set the label windows to limit the tool installer to agents with the windows label

  • Set the Download URL for binary archive as the URL of your locally downloaded copy of the MinGit zip file

  • Specify mingw64\bin\git.exe as the Subdirectory of extracted archive.

MinGit will be installed on each agent in tools\git\mingw64. The path to the git executable will be tools\git\mingw64\bin\git.exe.

Windows Credentials Manager

Git for Windows is able to integrate with the Windows Credentials Manager for secure storage of credentials. Windows Credentials Manager works very well for interactive users on the Windows desktop. Windows Credentials Manager does not work as well for batch processing in the git client plugin. It is best to disable Windows Credentials Manager when installing Git on Jenkins agents running Windows.

SSH Host Key verification

Git Client plugin provides various options to verify the SSH keys presented by Git repository host servers. By default, Git Client plugin uses the "Known hosts file" strategy to verify all host keys using the known_hosts file.

Host key verification strategies include:

Accept first connection

Remembers the first host key encountered for each git server and requires that the same host key must be use for later access. This is usually the most convenient setting for administrators while still providing ssh host key verification

Known hosts file

Uses the existing known_hosts file on the controller and on the agent. This assumes the administrator has already configured this file on the controller and on all agents

Manually provided keys

Provides a form field where the administrator inserts the host keys for the git repository servers. This works well when a small set of repository servers meet the needs of most users

No verification

Disables all verification of ssh host keys. Not recommended because it provides no protection from "man-in-the-middle" attacks

Configure the host key verification strategy from "Manage Jenkins" >> "Security" >> "Git Host Key Verification Configuration".

Configure Ssh host key verification
Note

OpenSSH releases prior to OpenSSH 7.6 (released Oct 2017) do not support the ssh command line argument used to accept first connection. Red Hat Enterprise Linux 7, CentOS 7, Oracle Linux 7, Scientific Linux 7, Amazon Linux 2, Debian 9, and Ubuntu 16.04 all deliver OpenSSH releases older than OpenSSH 7.6. The "Git Host Key Verification Configuration" for those systems cannot use the "Accept first connection" strategy with command line git.

Those operating systems are no longer supported by the Jenkins project. More details are available in the end of life operating systems blog post.

Users of those operating systems have the following options:

  • Upgrade to a supported operating system

  • Use the "Manually provided keys" host key verification strategy and provide host keys for their git hosts

  • Use the "Known hosts file" host key verification strategy and provide a known_hosts file on the agents with values for the required hosts

  • Enable JGit and use JGit instead of command line git on agents and controllers with those older OpenSSH versions

  • Switch the repository URL’s in job definitions from ssh protocol to https protocol and provide a username / password credential for the clone instead of a private key credential

  • Use the "No verification" host key verification strategy (not recommended)

Configuration as Code Sample

The configuration as code plugin can define the SSH host key verification strategy.

The "Accept first connection" host key verification strategy can be configured like this:

security:
  gitHostKeyVerificationConfiguration:
    sshHostKeyVerificationStrategy: "acceptFirstConnectionStrategy"

The "Known hosts file" host key verification strategy can be configured like this:

security:
  gitHostKeyVerificationConfiguration:
    sshHostKeyVerificationStrategy: "knownHostsFileVerificationStrategy"

The "Manually provided keys" host key verification strategy might be configured like this:

security:
  gitHostKeyVerificationConfiguration:
    sshHostKeyVerificationStrategy:
      manuallyProvidedKeyVerificationStrategy:
        approvedHostKeys: |-
          bitbucket.org ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIIazEu89wgQZ4bqs3d63QSMzYVa0MuJ2e2gKTKqu+UUO
          github.com ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOMqqnkVzrm0SdG6UOoqKLsabgH5C9okWi0dh2l9GKJl
          gitlab.com ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIAfuCHKVTjquxvt6CM6tdG4SLp1Btn/nOeHHE5UOzRdf

The "No verification" strategy (not recommended) can be configured like this:

security:
  gitHostKeyVerificationConfiguration:
    sshHostKeyVerificationStrategy: "noHostKeyVerificationStrategy"

Bug Reports

Report issues and enhancements with the Jenkins issue tracker. Please use the "How to Report an Issue" guidelines when reporting issues.

Contributing to the Plugin

Refer to contributing to the plugin for contribution guidelines.

Plugin Properties

Some plugin settings are controlled by Java system properties. The properties are often used to override a standard behavior or to revert to previous behavior. Refer to Jenkins Features Controlled with System Properties for more details on system properties and how to set them.

checkRemoteURL

When org.jenkinsci.plugins.gitclient.CliGitAPIImpl.checkRemoteURL is set to false it disables the safety checking of repository URLs.

Default is true so that repository URL’s are rejected if they start with - or contain space characters.

forceFetch

When org.jenkinsci.plugins.gitclient.CliGitAPIImpl.forceFetch is set to false it allows command line git versions 2.20 and later to not update tags which have already been fetched into the workspace.

Command line git 2.20 and later have changed behavior when fetching remote tags that already exist in the repository. Command line git before 2.20 silently updates an existing tag if the remote tag points to a different SHA1 than the local tag. Command line git 2.20 and later do not update an existing tag if the remote tag points to a different SHA1 than the local tag unless the --force option is passed to git fetch.

Default is true so that newer command line git versions behave the same as older versions.

promptForAuthentication

When org.jenkinsci.plugins.gitclient.CliGitAPIImpl.promptForAuthentication is set to true it allows command line git versions 2.3 and later to prompt the user for authentication. Command line git prompting for authentication should be rare, since Jenkins credentials should be managed through the credentials plugin.

Credential prompting could happen on multiple platforms, but is more common on Windows computers because many Windows agents run from the desktop environment. Agents running on the desktop are much less common in Unix environments.

Default is false so that command line git does not prompt for interactive authentication.

useCLI

When org.jenkinsci.plugins.gitclient.CliGitAPIImpl.useCLI is set to false, it will use JGit as the default implementation instead of command line git.

Default is true so that command line git is chosen as the default implementation.

user.name.file.encoding

When org.jenkinsci.plugins.gitclient.CliGitAPIImpl.user.name.file.encoding is set to a non-empty value (like IBM-1047) and the agent is running on IBM zOS, the username credentials file is written using that character set. The character sets of other credential files are not changed. The character sets on other operating systems are not changed.

Default is empty so that zOS file encoding behaves as it did previously.

user.passphrase.file.encoding

When org.jenkinsci.plugins.gitclient.CliGitAPIImpl.user.passphrase.file.encoding is set to a non-empty value (like IBM-1047) and the agent is running on IBM zOS, the ssh passphrase file is written using that character set. The character sets of other credential files are not changed. The character sets on other operating systems are not changed.

Default is empty so that zOS file encoding behaves as it did previously.

user.password.file.encoding

When org.jenkinsci.plugins.gitclient.CliGitAPIImpl.user.password.file.encoding is set to a non-empty value (like IBM-1047) and the agent is running on IBM zOS, the password file is written using that character set. The character sets of other credential files are not changed. The character sets on other operating systems are not changed.

Default is empty so that zOS file encoding behaves as it did previously.

useSETSID

When org.jenkinsci.plugins.gitclient.CliGitAPIImpl.useSETSID is set to true and the setsid command is available, the git client process on non-Windows computers will be started with the setsid command so that they are detached from any controlling terminal. Most agents are run without a controlling terminal and the useSETSID setting is not needed. Enable useSETSID only in those rare cases where the agent is running with a controlling terminal. If it is not used in those cases, the agent may block on some authenticated git operations.

This setting can be helpful with Jenkins swarm agents and inbound agents started from a terminal emulator.

Default is false so that setsid is not used.

Changelog in GitHub Releases

Release notes have been recorded in GitHub since git client plugin 2.8.1. Prior release notes were recorded in the git client plugin repository change log.