New day. Clear head.
Thanks for the help, it certainly lead me in the right direction.
The answer is there is a default global-ignore list that is built into subversion itself, not the config files, which was where the *.a ignore was coming from.
The global ignores in my config file looked like this:
#global-ignores = *.o *.lo *.la *.al .libs *.so *.so.[0-9]* *.a *.pyc *.pyo
# *.rej *~ #*# .#* .*.swp .DS_Store
I figured this was fine, because I didn't want to ignore anything. I was wrong because then subversion enforces its scarcely documented default global-ignores. I changed it to this, note the exclusion of '*.a'
global-ignores = *.o *.lo *.la *.al .libs *.so *.so.[0-9]* *.pyc *.pyo
*.rej *~ #*# .#* .*.swp .DS_Store
At this point *.a files are no longer ignores, and my .DS_Store file is still ignored, and all is right in my world.
As GraemeF suggested, propget does not retrieve global values for svn:ignore. As Ether suggested, you can add ignored files by naming them explicitly.
The best link I found was here:
http://svn.haxx.se/users/archive-2009-02/0725.shtml
This post says to me that there is a non-empty default value for global-ignores that is used if global-ignores is not set in the config file.