I read the subversion book and it is clear to me that subversion does not store individual files but only deltas in order to minimize disk space. Subversion also does the sa
From the Subversion Design document (which is quite dated, though) you can get this:
Like many other revision control systems, Subversion stores changes as differences. It doesn't make complete copies of nodes; instead, it stores the latest revision as a full text, and previous revisions as a succession of reverse diffs (the word "diff" is used loosely here – for files, it means vdeltas, for directories, it means a format that expresses changes to directories).
I don't think that was changed since.
Also, see Bubble-Up Method.