git rev-list | git cherry-pick --stdin is leaky

(resending since the attachment seems to make vger sad)

Hi,

I'm running git rev-list | git cherry-pick --stdin on a range of about 300 commits. Eventually the chery-pick dies with:

    error: cannot fork() for commit: Cannot allocate memory

Running valgrind shows me that the tree traversal code is leaking gigabytes of memory (particularly unpack_callback). Since cherry-pick is a very long running process all these allocations are never freed and eventually I run out of memory. The worst offender and summary is:

==7986== 938,956,692 (929,961,582 direct, 8,995,110 indirect) bytes in 7,765,439 blocks are definitely lost in loss record 257 of 257 ==7986== at 0x4C267CC: calloc (vg_replace_malloc.c:467) ==7986== by 0x4FAF57: xcalloc (wrapper.c:119) ==7986== by 0x4F5281: unpack_callback (unpack-trees.c:539) ==7986== by 0x4F40E5: traverse_trees (tree-walk.c:407) ==7986== by 0x4F586C: unpack_callback (unpack-trees.c:467) ==7986== by 0x4F40E5: traverse_trees (tree-walk.c:407) ==7986== by 0x4F586C: unpack_callback (unpack-trees.c:467) ==7986== by 0x4F40E5: traverse_trees (tree-walk.c:407) ==7986== by 0x4F586C: unpack_callback (unpack-trees.c:467) ==7986== by 0x4F40E5: traverse_trees (tree-walk.c:407) ==7986== by 0x4F586C: unpack_callback (unpack-trees.c:467) ==7986== by 0x4F40E5: traverse_trees (tree-walk.c:407) ==7986== ==7986== LEAK SUMMARY: ==7986== definitely lost: 2,514,117,692 bytes in 21,210,861 blocks ==7986== indirectly lost: 885,481,947 bytes in 10,165,801 blocks ==7986== possibly lost: 650,712,395 bytes in 6,014,309 blocks ==7986== still reachable: 7,734,870 bytes in 47,794 blocks ==7986== suppressed: 0 bytes in 0 blocks

This is against recent git.git (89740333e8d398f1da701e9023675321bbb9a85b). A workaround is to limit the amount of commits per cherry-pick invocation, but can we somehow fix the leaks?