VERY slow git format-patch (tens on minutes) during rebase and rev-list during rebase -i

[Marat Radchenko <marat@slonopotamus.org>]

Hi.

My setup:
0. Quad-code machine with 8GB of ram, 10K RPM hdd.
1. SVN repo that i periodically fetch into origin/trunk branch. Has ~200 
commits/day.
2. My local branch with 1-5 commits which i often rebase against trunk.
3. I haven't rebased for 2 days, so i'm rebasing 3 (three) commits in my branch 
over 453 commits in trunk using "git rebase trunk".
4. trunk does contain "bad" from diff POV files (big & binary).
5. Sadly, data in repo is confidential.

Expected: rebase takes some reasonable amount of time (< 1 min?).

Actual: rebase takes 20 mins.

Almost all of that time was spent doing `git format-patch -k --stdout --full-
index --ignore-if-in-upstream 
80bb0dfe3d86f3cc9095ea616d9d1b1530fbe7b8..d3fde4ae7497981a6fe61b0366b105477896cf
52` (that's three commits from my branch) at 100% of one CPU core.

Additional info:

Another similar rebase but over 4.5k of commits took 2 hours.

Running without --ignore-if-in-upstream:
$ time git format-patch -k --stdout --full-index 
80bb0dfe3d86f3cc9095ea616d9d1b1530fbe7b8..d3fde4ae7497981a6fe61b0366b105477896cf
5 | wc -l
25823
Is it 
real	0m0.163s
user	0m0.140s
sys	0m0.020s

Proof there are only three commits:

$ git rev-list 
80bb0dfe3d86f3cc9095ea616d9d1b1530fbe7b8..d3fde4ae7497981a6fe61b0366b105477896cf
52d3fde4ae7497981a6fe61b0366b105477896cf52
e18069258806bda6a6165822003f5e9fd958f906
c8c2f2e157e615b73d0baab1d793a22991c9ba71

Questions:
1. Is it expected behavior (branch you rebase onto has binary files -> no 
performance for you)?
2. If [1] is yes, is it possible to prevent rebase from running --ignore-if-in-
upstream?
3. If [1] is no, should i run some kind of profiler (how?) to determine what 
exactly causes such performance drop?