Question

As I am learning Git, I get to know that the other VCS systems like SVN usually store changes to a base version of files. So, as a logical deduction, if I want to check out the version 4 of the file A, the SVN will patch the base version file on-the-fly with all the change sets commited until version 4 before delivering the verion I want?

The following picture may be helpful.

In short, only the base version file is stored statically, all the other versions are dynamically generated with base file and necessary change sets.

right?

Thanks.

Answer 1

From Subversion Design doc:

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).

Important point is that, the latest revision is the base and (reverse) diffs are stored from that backwards.

http://svn.apache.org/repos/asf/subversion/trunk/notes/subversion-design.html#server.fs.struct

You can also look at the link to see how the commit gets stored in the repository.