SINCE 1.5.0
Gitblit supports extending and enhancing the core functionality through plugins. This mechanism is very young and incomplete with few extension points, but you can expect it to evolve rapidly in upcoming releases.
A plugin is a collection of Java classes and required jar dependencies bundled together in a zip file. A plugin may optionally include Extensions which enhance Gitblit at specific Gitblit-specified ExtensionPoints.
Plugins are singleton instances that are STARTED when Gitblit launches and STOPPED when Gitblit terminates. Extensions are dynamic instances that are created when Gitblit processes requests that trigger ExtensionPoints.
The existing plugin mechanism is based on pf4j. Plugins are distributed as zip files and may include their runtime dependencies or may rely on the bundled dependencies of other plugins and/or Gitblit core.
The zip plugins are stored in ${baseFolder}/plugins and are unpacked on startup into folders of the same name.
A plugin defines it's metadata in the META-INF/MANIFEST.MF file:
Plugin-Id: powertools
Plugin-Description: Command and control Gitblit over SSH
Plugin-Class: com.gitblit.plugin.powertools.Powertools
Plugin-Version: 1.2.0
Plugin-Provider: gitblit.com
In addition to extending Gitblit core, plugins can also define extension points that may be implemented by other plugins. Therefore a plugin may depend on other plugins.
Plugin-Dependencies: foo, bar
NOTE:
The pf4j plugin framework relies on a javac apt processor to generate compile-time extension information, so be sure to enable apt processing in your build process.
Plugins may specify dependencies by ID, but may not specify specific versions of a dependency. The plugin registry allows you to specify a requires version of Gitblit, but this is not currently enforced.
Administrators may manage plugins through the plugin SSH dispatch command:
ssh host plugin
Through this command interface plugins can be started, stopped, disabled, enabled, installed, uninstalled, listed, etc.
Gitblit provides a simple default registry of plugins. The registry is a JSON file and it lists plugin metadata and download locations.
plugins.registry = http://plugins.gitblit.com/plugins.json
The registry is currently hosted in a Git repository on Github. This git repository is also a Maven-compatible repository, which hosts some plugin binaries.
If you develop your own plugins that you want hosted by or linked in the default registry, open pull request for the registry repository. Any contributed binaries hosted in this repository must have Maven metadata and the SHA-1 & MD5 checksums. By default, Gitblit enforces checksum validation on all downloads.
The plugins.json file is parameterized with the ${self} placeholder. This parameter is substituted on download with with the source URL of the registry file. This allows you to clone and serve your own copy of this git repository or just server your own plugins.json on your own network.
Gitblit also supports loading multiple plugin registries. Just place another properly formatted .json file in ${baseFolder}/plugins and Gitblit will load that as an additional registry.
Gitblit's core SSH commands and those in the powertools plugin rely on ANSI border characters to provide a pretty presentation of data. Unfortunately, the fonts provided by Apple - while very nice - don't work well with ANSI border characters. The following public domain fixed-width, fixed-point, bitmapped fonts work very nicely. I find the 6x12 font with a line spacing of ~0.8 to be quite acceptable.