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pack-refs: add fully-peeled trait

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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>
This commit is contained in:
Michael Haggerty
2013-03-18 07:37:32 -04:00
committed by Junio C Hamano
parent 03a8eddfd1
commit c29c46fa2e
3 changed files with 67 additions and 6 deletions
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22
t/t3211-peel-ref.sh
View File

@ -39,4 +39,26 @@ test_expect_success 'refs are peeled outside of refs/tags (packed)' '
test_cmp expect actual
'
test_expect_success 'create old-style pack-refs without fully-peeled' '
# Git no longer writes without fully-peeled, so we just write our own
# from scratch; we could also munge the existing file to remove the
# fully-peeled bits, but that seems even more prone to failure,
# especially if the format ever changes again. At least this way we
# know we are emulating exactly what an older git would have written.
{
echo "# pack-refs with: peeled " &&
print_ref "refs/heads/master" &&
print_ref "refs/outside/foo" &&
print_ref "refs/tags/base" &&
print_ref "refs/tags/foo" &&
echo "^$(git rev-parse "refs/tags/foo^{}")"
} >tmp &&
mv tmp .git/packed-refs
'
test_expect_success 'refs are peeled outside of refs/tags (old packed)' '
git show-ref -d >actual &&
test_cmp expect actual
'
test_done