[Bug-tar] creating identical .tar.gz files for use with version control

[Chris Pickett]

Hi,

I am checking .tar.gz files into subversion for some data in directories 
because the uncompressed files inside are too large.

For example:

tar cvfz a.tar.gz a/
svn add a.tar.gz
svn ci

However, if I repeat the process without changing the underlying files, 
a.tar.gz is different, and thus it needs to get checked in again.

Is there an option set I can use to prevent this?  I am using tar-1.19.

Thanks,
Chris