kernel/git - git - PowerEL Git System

Author	SHA1	Message	Date
Michael Haggerty	694b7a1999	repack_without_ref(): write peeled refs in the rewritten file When a reference that existed in the packed-refs file is deleted, the packed-refs file must be rewritten. Previously, the file was rewritten without any peeled refs, even if the file contained peeled refs when it was read. This was not a bug, because the packed-refs file header didn't claim that the file contained peeled values. But it had a performance cost, because the repository would lose the benefit of having precomputed peeled references until pack-refs was run again. Teach repack_without_ref() to write peeled refs to the packed-refs file (regardless of whether they were present in the old version of the file). This means that if the old version of the packed-refs file was not fully peeled, then repack_without_ref() will have to peel references. To avoid the expense of reading lots of loose references, we take two shortcuts relative to pack-refs: * If the peeled value of a reference is already known (i.e., because it was read from the old version of the packed-refs file), then output that peeled value again without any checks. This is the usual code path and should avoid any noticeable overhead. (This is different than pack-refs, which always re-peels references.) * We don't verify that the packed ref is still current. It could be that a packed references is overridden by a loose reference, in which case the packed ref is no longer needed and might even refer to an object that has been garbage collected. But we don't check; instead, we just try to peel all references. If peeling is successful, the peeled value is written out (even though it might not be needed any more); if not, then the reference is silently omitted from the output. The extra overhead of peeling references in repack_without_ref() should only be incurred the first time the packed-refs file is written by a version of Git that knows about the "fully-peeled" attribute. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	12 years ago
Michael Haggerty	c995de61cd	t3211: demonstrate loss of peeled refs if a packed ref is deleted Add a test that demonstrates that the peeled values recorded in packed-refs are lost if a packed ref is deleted. (The code in repack_without_ref() doesn't even attempt to write peeled refs.) This will be fixed in a moment. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>	12 years ago
Michael Haggerty	c29c46fa2e	pack-refs: add fully-peeled trait Older versions of pack-refs did not write peel lines for refs outside of refs/tags. This meant that on reading the pack-refs file, we might set the REF_KNOWS_PEELED flag for such a ref, even though we do not know anything about its peeled value. The previous commit updated the writer to always peel, no matter what the ref is. That means that packed-refs files written by newer versions of git are fine to be read by both old and new versions of git. However, we still have the problem of reading packed-refs files written by older versions of git, or by other implementations which have not yet learned the same trick. The simplest fix would be to always unset the REF_KNOWS_PEELED flag for refs outside of refs/tags that do not have a peel line (if it has a peel line, we know it is valid, but we cannot assume a missing peel line means anything). But that loses an important optimization, as upload-pack should not need to load the object pointed to by refs/heads/foo to determine that it is not a tag. Instead, we add a "fully-peeled" trait to the packed-refs file. If it is set, we know that we can trust a missing peel line to mean that a ref cannot be peeled. Otherwise, we fall back to assuming nothing. [commit message and tests by Jeff King <peff@peff.net>] Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	12 years ago
Jeff King	03a8eddfd1	pack-refs: write peeled entry for non-tags When we pack an annotated tag ref, we write not only the sha1 of the tag object along with the ref, but also the sha1 obtained by peeling the tag. This lets readers of the pack-refs file know the peeled value without having to actually load the object, speeding up upload-pack's ref advertisement. The writer marks a packed-refs file with peeled refs using the "peeled" trait at the top of the file. When the reader sees this trait, it knows that each ref is either followed by its peeled value, or it is not an annotated tag. However, there is a mismatch between the assumptions of the reader and writer. The writer will only peel refs under refs/tags, but the reader does not know this; it will assume a ref without a peeled value must not be a tag object. Thus an annotated tag object placed outside of the refs/tags hierarchy will not have its peeled value printed by upload-pack. The simplest way to fix this is to start writing peel values for all refs. This matches what the reader expects for both new and old versions of git. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	12 years ago