Version Control with Subversion - Login

Embedding SubversionAs we mentioned earlier, the libsvn_fs API looks and feels like any other filesystem, exceptthat it has this wonderful versioning capability. It was designed to be usable by anyprogram interested in a versioning filesystem. Not coincidentally, Subversion itself is interestedin that functionality. But while the filesystem API should be sufficient for basic file anddirectory versioning support, Subversion wants more—and that is where libsvn_reposcomes in.The Subversion repository library (libsvn_repos) sits (logically speaking) atop thelibsvn_fs API, providing additional functionality beyond that of the underlying versionedfilesystem logic. It does not completely wrap each and every filesystem function—only certainmajor steps in the general cycle of filesystem activity are wrapped by the repository interface.Some of these include the creation and commit of Subversion transactions and themodification of revision properties. These particular events are wrapped by the repositorylayer because they have hooks associated with them. A repository hook system is notstrictly related to implementing a versioning filesystem, so it lives in the repository wrapperlibrary.The hooks mechanism is but one of the reasons for the abstraction of a separate repositorylibrary from the rest of the filesystem code. The libsvn_repos API provides severalother important utilities to Subversion. These include the abilities to:• Create, open, destroy, and perform recovery steps on a Subversion repository and thefilesystem included in that repository.• Describe the differences between two filesystem trees.• Query for the commit log messages associated with all (or some) of the revisions inwhich a set of files was modified in the filesystem.• Generate a human-readable “dump” of the filesystem—a complete representation of therevisions in the filesystem.• Parse that dump format, loading the dumped revisions into a different Subversion repository.As Subversion continues to evolve, the repository library will grow with the filesystem libraryto offer increased functionality and configurable option support.Repository Access Layer210