As we mentioned earlier, each directory of a Subversion
working copy contains a special subdirectory called
.svn that houses administrative data about
that working copy directory. Subversion uses the information in
.svn to keep track of things such as:
Which repository location(s) are represented by the files and subdirectories in the working copy directory
What revision of each of those files and directories is currently present in the working copy
Any user-defined properties that might be attached to those files and directories
Pristine (unedited) copies of the working copy files
The Subversion working copy administration area's layout and contents are considered implementation details not really intended for human consumption. Developers are encouraged to use Subversion's public APIs, or the tools that Subversion provides, to access and manipulate the working copy data, instead of directly reading or modifying those files. The file formats employed by the working copy library for its administrative data do change from time to time—a fact that the public APIs do a great job of hiding from the average user. In this section, we expose some of these implementation details sheerly to appease your overwhelming curiosity.
Perhaps the single most important file in the
.svn directory is the
entries file. It
contains the bulk of the administrative
information about the versioned items in a working copy
directory. This one file tracks the repository
URLs, pristine revision, file checksums, pristine text and
property timestamps, scheduling and conflict state
information, last-known commit information (author, revision,
timestamp), local copy history—practically everything
that a Subversion client is interested in knowing about a
versioned (or to-be-versioned) resource!
Folks familiar with CVS's administrative directories will
have recognized at this point that Subversion's
.svn/entries file serves the purposes of,
among other things, CVS's CVS/Entries,
CVS/Root, and
CVS/Repository files combined.
The format of the .svn/entries file
has changed over time. Originally an XML file, it now uses a
custom—though still human-readable—file format.
While XML was a great choice for early developers of
Subversion who were frequently debugging the file's contents
(and Subversion's behavior in light of them), the need for
easy developer debugging has diminished as Subversion has
matured and has been replaced by the user's need for snappier
performance. Be aware that Subversion's working copy library
automatically upgrades working copies from one format to
another—it reads the old formats and writes the
new—which saves you the hassle of checking out a new
working copy, but can also complicate situations where
different versions of Subversion might be trying to use the
same working copy.
As mentioned before, the .svn
directory also holds the pristine “text-base”
versions of files. You can find those in
.svn/text-base. The benefits of these
pristine copies are multiple—network-free checks for
local modifications and difference reporting, network-free
reversion of modified or missing files, more efficient
transmission of changes to the server—but they come at the
cost of having each versioned file stored at least twice on
disk. These days, this seems to be a negligible penalty for
most files. However, the situation gets uglier as the size of
your versioned files grows. Some attention is being given to
making the presence of the “text-base” an option.
Ironically, though, it is as your versioned files' sizes get
larger that the existence of the “text-base”
becomes more crucial—who wants to transmit a huge file
across a network just because she wants to commit a tiny
change to it?
Similar in purpose to the “text-base” files
are the property files and their pristine
“prop-base” copies, located in
.svn/props and
.svn/prop-base, respectively. Since
directories can have properties too, there are also
.svn/dir-props and
.svn/dir-prop-base files.