StGIT 0.12.1: pulling up to specific commit (tag)

After update to 0.12 I am a bit lost how to do it.

I have local branch for kernel tree that contains several patches. I do not 
want this tree to be up-to-date with the latest commits upstream, rather I 
need it on (sub-)version basis. But there is apparently no way to say in 
stgit "please pull up to specific commit".

What I did before 0.12 was

git branch b2.6.21-rc3 v2.6.21-rc3
stg pull . b2.6.21-rc3

Now "stg pull" no more accepts branch name; but I cannot figure how to to the 
same using git config. I have:

branch.cooker.merge=stgit
branch.cooker.remote=stgit

then I do

git branch stgit v2.6.21-rc3
stg pull .

This always results in "up to date" message and nothing is actually merged in 
current branch. But if I do

stg pop -a
git pull . stgit

then changes *are* merged as expected

So for now I have a workaround, but it is rather awkward. May be I am doing it 
the wrong way and I should just do "stg pull; git reset" but I had bad 
experience with mixing stgit and git tree/index manipulation commands in the 
past.

TIA

-andrey