multiple branch shallow clones and object sharing

Hi,
Say, I would like to get just the recent history of two branches of a
big project with, for example:
git clone -b REL-1_10_0_PATCHES --depth  99
git://git.postgresql.org/git/pgadmin3.git pgadmin-1.10
git clone -b REL-1_12_0_PATCHES --depth 299
git://git.postgresql.org/git/pgadmin3.git pgadmin-1.12

If the 1st one were not a shallow clone, we could have --referenced it
in the 2nd command to avoid unnecassary downloads of many objects, but
since the history of the project is very big we just want some recent
history. Is the following commandline syntax too absurd/naive for a
new feature of git :?

git clone -b REL-1_10_0_PATCHES --depth 99 -b REL-1_12_0_PATCHES
--depth 299 git://git.postgresql.org/git/pgadmin3.git pgadmin-1.10
pgadmin-1.12

this is supposed to download the two branches simultaneously into two
respective local directories, making any possible download savings
along the way.

Thanks,
Serhat