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git/t/t3211-peel-ref.sh
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>
2013-05-01 15:33:10 -07:00

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#!/bin/sh
test_description='tests for the peel_ref optimization of packed-refs'
. ./test-lib.sh
test_expect_success 'create annotated tag in refs/tags' '
test_commit base &&
git tag -m annotated foo
'
test_expect_success 'create annotated tag outside of refs/tags' '
git update-ref refs/outside/foo refs/tags/foo
'
# This matches show-ref's output
print_ref() {
echo "$(git rev-parse "$1") $1"
}
test_expect_success 'set up expected show-ref output' '
{
print_ref "refs/heads/master" &&
print_ref "refs/outside/foo" &&
print_ref "refs/outside/foo^{}" &&
print_ref "refs/tags/base" &&
print_ref "refs/tags/foo" &&
print_ref "refs/tags/foo^{}"
} >expect
'
test_expect_success 'refs are peeled outside of refs/tags (loose)' '
git show-ref -d >actual &&
test_cmp expect actual
'
test_expect_success 'refs are peeled outside of refs/tags (packed)' '
git pack-refs --all &&
git show-ref -d >actual &&
test_cmp expect actual
'
test_expect_success 'create old-style pack-refs without fully-peeled' '
# Git no longer writes without fully-peeled, so we just write our own
# from scratch; we could also munge the existing file to remove the
# fully-peeled bits, but that seems even more prone to failure,
# especially if the format ever changes again. At least this way we
# know we are emulating exactly what an older git would have written.
{
echo "# pack-refs with: peeled " &&
print_ref "refs/heads/master" &&
print_ref "refs/outside/foo" &&
print_ref "refs/tags/base" &&
print_ref "refs/tags/foo" &&
echo "^$(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_expect_success 'peeled refs survive deletion of packed ref' '
git pack-refs --all &&
cp .git/packed-refs fully-peeled &&
git branch yadda &&
git pack-refs --all &&
git branch -d yadda &&
test_cmp fully-peeled .git/packed-refs
'
test_done