index-pack: use streaming interface on large blobs (most of the time)
unpack_raw_entry() will not allocate and return decompressed blobs if they are larger than core.bigFileThreshold. sha1_object() may not be called on those objects because there's no actual content. sha1_object() is called later on those objects, where we can safely use get_data_from_pack() to retrieve blob content for checking. However we always do that when we definitely need the blob content. And we often don't. There are two cases when we may need object content. The first case is when we find an in-repo blob with the same SHA-1. We need to do collision test, byte-on-byte. If this test is on, the blob must be loaded on memory (i.e. no streaming). Normally (e.g. in fetch/pull/clone) this does not happen because git avoid to send objects that client already has. The other case is when --strict is specified and the object in question is not a blob, which can't happen in reality becase we deal with large _blobs_ here. Note: --verify (or git-verify-pack) a pack from current repository will trigger collision test on every object in the pack, which effectively disables this patch. This could be easily worked around by setting GIT_DIR to an imaginary place with no packs. Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: NJunio C Hamano <gitster@pobox.com>
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