Back when we switched pack-objects to visiting packs in
most-recently-used order last August, we realized that this could reuse
cross-pack deltas, and that the result could have longer delta chains
than any single pack contains.
I produced a patch back then[1], but we decided not to follow through
with it. Two things happened to make me revive that patch:
1. I hit a case in the wild with a really long delta chain that caused
pack-objects' write_one() to run out of stack space.
2. We dropped the --aggressive depth to match the normal one. So
there's less concern about mismatches throwing out on-disk deltas
from a previous aggressive repack (but see the caveats in the first
patch's commit message).
So here it is, plus another patch that converts the recursion to
iteration (the stack space needed by the function is small enough that
just the first patch was enough to fix my problem case, but it seemed
like tempting fate to leave it recursive).
[1/2]: pack-objects: enforce --depth limit in reused deltas
[2/2]: pack-objects: convert recursion to iteration in break_delta_chain()
builtin/pack-objects.c | 133 ++++++++++++++++++++++++++++++++++++--------
pack-objects.h | 4 ++
t/t5316-pack-delta-depth.sh | 93 +++++++++++++++++++++++++++++++
3 files changed, 207 insertions(+), 23 deletions(-)
create mode 100755 t/t5316-pack-delta-depth.sh
-Peff
[1] http://public-inbox.org/git/20160811095710.p2bffympjlwmv3gc@xxxxxxxxxxxxxxxxxxxxx/