This section is from the "Version Control with Subversion" book, by Ben Collins-Sussman, Brian W. Fitzpatrick and C. Michael Pilato. Also available from Amazon: Version Control with Subversion.
As mentioned before, the .svn
directory also holds the pristine “text-base”
versions of files. Those can be found 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 comes 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 they want 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.