prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
#!/bin/sh
|
|
|
|
#
|
|
|
|
# This test covers the handling of objects which might have old
|
|
|
|
# mtimes in the filesystem (because they were used previously)
|
|
|
|
# and are just now becoming referenced again.
|
|
|
|
#
|
|
|
|
# We're going to do two things that are a little bit "fake" to
|
|
|
|
# help make our simulation easier:
|
|
|
|
#
|
|
|
|
# 1. We'll turn off reflogs. You can still run into
|
|
|
|
# problems with reflogs on, but your objects
|
|
|
|
# don't get pruned until both the reflog expiration
|
|
|
|
# has passed on their references, _and_ they are out
|
|
|
|
# of prune's expiration period. Dropping reflogs
|
|
|
|
# means we only have to deal with one variable in our tests,
|
|
|
|
# but the results generalize.
|
|
|
|
#
|
|
|
|
# 2. We'll use a temporary index file to create our
|
|
|
|
# works-in-progress. Most workflows would mention
|
|
|
|
# referenced objects in the index, which prune takes
|
|
|
|
# into account. However, many operations don't. For
|
|
|
|
# example, a partial commit with "git commit foo"
|
|
|
|
# will use a temporary index. Or they may not need
|
|
|
|
# an index at all (e.g., creating a new commit
|
|
|
|
# to refer to an existing tree).
|
|
|
|
|
|
|
|
test_description='check pruning of dependent objects'
|
2020-11-18 23:44:38 +00:00
|
|
|
GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
|
tests: mark tests relying on the current default for `init.defaultBranch`
In addition to the manual adjustment to let the `linux-gcc` CI job run
the test suite with `master` and then with `main`, this patch makes sure
that GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME is set in all test scripts
that currently rely on the initial branch name being `master by default.
To determine which test scripts to mark up, the first step was to
force-set the default branch name to `master` in
- all test scripts that contain the keyword `master`,
- t4211, which expects `t/t4211/history.export` with a hard-coded ref to
initialize the default branch,
- t5560 because it sources `t/t556x_common` which uses `master`,
- t8002 and t8012 because both source `t/annotate-tests.sh` which also
uses `master`)
This trick was performed by this command:
$ sed -i '/^ *\. \.\/\(test-lib\|lib-\(bash\|cvs\|git-svn\)\|gitweb-lib\)\.sh$/i\
GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master\
export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME\
' $(git grep -l master t/t[0-9]*.sh) \
t/t4211*.sh t/t5560*.sh t/t8002*.sh t/t8012*.sh
After that, careful, manual inspection revealed that some of the test
scripts containing the needle `master` do not actually rely on a
specific default branch name: either they mention `master` only in a
comment, or they initialize that branch specificially, or they do not
actually refer to the current default branch. Therefore, the
aforementioned modification was undone in those test scripts thusly:
$ git checkout HEAD -- \
t/t0027-auto-crlf.sh t/t0060-path-utils.sh \
t/t1011-read-tree-sparse-checkout.sh \
t/t1305-config-include.sh t/t1309-early-config.sh \
t/t1402-check-ref-format.sh t/t1450-fsck.sh \
t/t2024-checkout-dwim.sh \
t/t2106-update-index-assume-unchanged.sh \
t/t3040-subprojects-basic.sh t/t3301-notes.sh \
t/t3308-notes-merge.sh t/t3423-rebase-reword.sh \
t/t3436-rebase-more-options.sh \
t/t4015-diff-whitespace.sh t/t4257-am-interactive.sh \
t/t5323-pack-redundant.sh t/t5401-update-hooks.sh \
t/t5511-refspec.sh t/t5526-fetch-submodules.sh \
t/t5529-push-errors.sh t/t5530-upload-pack-error.sh \
t/t5548-push-porcelain.sh \
t/t5552-skipping-fetch-negotiator.sh \
t/t5572-pull-submodule.sh t/t5608-clone-2gb.sh \
t/t5614-clone-submodules-shallow.sh \
t/t7508-status.sh t/t7606-merge-custom.sh \
t/t9302-fast-import-unpack-limit.sh
We excluded one set of test scripts in these commands, though: the range
of `git p4` tests. The reason? `git p4` stores the (foreign) remote
branch in the branch called `p4/master`, which is obviously not the
default branch. Manual analysis revealed that only five of these tests
actually require a specific default branch name to pass; They were
modified thusly:
$ sed -i '/^ *\. \.\/lib-git-p4\.sh$/i\
GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=master\
export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME\
' t/t980[0167]*.sh t/t9811*.sh
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-11-18 23:44:19 +00:00
|
|
|
export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
|
|
|
|
|
tests: mark tests as passing with SANITIZE=leak
When the "ab/various-leak-fixes" topic was merged in [1] only t6021
would fail if the tests were run in the
"GIT_TEST_PASSING_SANITIZE_LEAK=check" mode, i.e. to check whether we
marked all leak-free tests with "TEST_PASSES_SANITIZE_LEAK=true".
Since then we've had various tests starting to pass under
SANITIZE=leak. Let's mark those as passing, this is when they started
to pass, narrowed down with "git bisect":
- t5317-pack-objects-filter-objects.sh: In
faebba436e6 (list-objects-filter: plug pattern_list leak, 2022-12-01).
- t3210-pack-refs.sh, t5613-info-alternate.sh,
t7403-submodule-sync.sh: In 189e97bc4ba (diff: remove parseopts member
from struct diff_options, 2022-12-01).
- t1408-packed-refs.sh: In ab91f6b7c42 (Merge branch
'rs/diff-parseopts', 2022-12-19).
- t0023-crlf-am.sh, t4152-am-subjects.sh, t4254-am-corrupt.sh,
t4256-am-format-flowed.sh, t4257-am-interactive.sh,
t5403-post-checkout-hook.sh: In a658e881c13 (am: don't pass strvec to
apply_parse_options(), 2022-12-13)
- t1301-shared-repo.sh, t1302-repo-version.sh: In b07a819c05f (reflog:
clear leftovers in reflog_expiry_cleanup(), 2022-12-13).
- t1304-default-acl.sh, t1410-reflog.sh,
t5330-no-lazy-fetch-with-commit-graph.sh, t5502-quickfetch.sh,
t5604-clone-reference.sh, t6014-rev-list-all.sh,
t7701-repack-unpack-unreachable.sh: In b0c61be3209 (Merge branch
'rs/reflog-expiry-cleanup', 2022-12-26)
- t3800-mktag.sh, t5302-pack-index.sh, t5306-pack-nobase.sh,
t5573-pull-verify-signatures.sh, t7612-merge-verify-signatures.sh: In
69bbbe484ba (hash-object: use fsck for object checks, 2023-01-18).
- t1451-fsck-buffer.sh: In 8e4309038f0 (fsck: do not assume
NUL-termination of buffers, 2023-01-19).
- t6501-freshen-objects.sh: In abf2bb895b4 (Merge branch
'jk/hash-object-fsck', 2023-01-30)
1. 9ea1378d046 (Merge branch 'ab/various-leak-fixes', 2022-12-14)
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-02-06 23:07:36 +00:00
|
|
|
TEST_PASSES_SANITIZE_LEAK=true
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
. ./test-lib.sh
|
|
|
|
|
|
|
|
# We care about reachability, so we do not want to use
|
|
|
|
# the normal test_commit, which creates extra tags.
|
|
|
|
add () {
|
|
|
|
echo "$1" >"$1" &&
|
|
|
|
git add "$1"
|
|
|
|
}
|
|
|
|
commit () {
|
|
|
|
test_tick &&
|
|
|
|
add "$1" &&
|
|
|
|
git commit -m "$1"
|
|
|
|
}
|
|
|
|
|
2014-10-15 22:42:09 +00:00
|
|
|
maybe_repack () {
|
prune: save reachable-from-recent objects with bitmaps
We pass our prune expiration to mark_reachable_objects(), which will
traverse not only the reachable objects, but consider any recent ones as
tips for reachability; see d3038d22f9 (prune: keep objects reachable
from recent objects, 2014-10-15) for details.
However, this interacts badly with the bitmap code path added in
fde67d6896 (prune: use bitmaps for reachability traversal, 2019-02-13).
If we hit the bitmap-optimized path, we return immediately to avoid the
regular traversal, accidentally skipping the "also traverse recent"
code.
Instead, we should do an if-else for the bitmap versus regular
traversal, and then follow up with the "recent" traversal in either
case. This reuses the "rev_info" for a bitmap and then a regular
traversal, but that should work OK (the bitmap code clears the pending
array in the usual way, just like a regular traversal would).
Note that I dropped the comment above the regular traversal here. It
has little explanatory value, and makes the if-else logic much harder to
read.
Here are a few variants that I rejected:
- it seems like both the reachability and recent traversals could be
done in a single traversal. This was rejected by d3038d22f9 (prune:
keep objects reachable from recent objects, 2014-10-15), though the
balance may be different when using bitmaps. However, there's a
subtle correctness issue, too: we use revs->ignore_missing_links for
the recent traversal, but not the reachability one.
- we could try using bitmaps for the recent traversal, too, which
could possibly improve performance. But it would require some fixes
in the bitmap code, which uses ignore_missing_links for its own
purposes. Plus it would probably not help all that much in practice.
We use the reachable tips to generate bitmaps, so those objects are
likely not covered by bitmaps (unless they just became unreachable).
And in general, we expect the set of unreachable objects to be much
smaller anyway, so there's less to gain.
The test in t5304 detects the bug and confirms the fix.
I also beefed up the tests in t6501, which covers the mtime-checking
code more thoroughly, to handle the bitmap case (in addition to just
"loose" and "packed" cases). Interestingly, this test doesn't actually
detect the bug, because it is running "git gc", and not "prune"
directly. And "gc" will call "repack" first, which does not suffer the
same bug. So the old-but-reachable-from-recent objects get scooped up
into the new pack along with the actually-recent objects, which gives
both a recent mtime. But it seemed prudent to get more coverage of the
bitmap case for related code.
Reported-by: David Emett <dave@sp4m.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-04-28 15:42:43 +00:00
|
|
|
case "$title" in
|
|
|
|
loose)
|
|
|
|
: skip repack
|
|
|
|
;;
|
|
|
|
repack)
|
2014-10-15 22:42:09 +00:00
|
|
|
git repack -ad
|
prune: save reachable-from-recent objects with bitmaps
We pass our prune expiration to mark_reachable_objects(), which will
traverse not only the reachable objects, but consider any recent ones as
tips for reachability; see d3038d22f9 (prune: keep objects reachable
from recent objects, 2014-10-15) for details.
However, this interacts badly with the bitmap code path added in
fde67d6896 (prune: use bitmaps for reachability traversal, 2019-02-13).
If we hit the bitmap-optimized path, we return immediately to avoid the
regular traversal, accidentally skipping the "also traverse recent"
code.
Instead, we should do an if-else for the bitmap versus regular
traversal, and then follow up with the "recent" traversal in either
case. This reuses the "rev_info" for a bitmap and then a regular
traversal, but that should work OK (the bitmap code clears the pending
array in the usual way, just like a regular traversal would).
Note that I dropped the comment above the regular traversal here. It
has little explanatory value, and makes the if-else logic much harder to
read.
Here are a few variants that I rejected:
- it seems like both the reachability and recent traversals could be
done in a single traversal. This was rejected by d3038d22f9 (prune:
keep objects reachable from recent objects, 2014-10-15), though the
balance may be different when using bitmaps. However, there's a
subtle correctness issue, too: we use revs->ignore_missing_links for
the recent traversal, but not the reachability one.
- we could try using bitmaps for the recent traversal, too, which
could possibly improve performance. But it would require some fixes
in the bitmap code, which uses ignore_missing_links for its own
purposes. Plus it would probably not help all that much in practice.
We use the reachable tips to generate bitmaps, so those objects are
likely not covered by bitmaps (unless they just became unreachable).
And in general, we expect the set of unreachable objects to be much
smaller anyway, so there's less to gain.
The test in t5304 detects the bug and confirms the fix.
I also beefed up the tests in t6501, which covers the mtime-checking
code more thoroughly, to handle the bitmap case (in addition to just
"loose" and "packed" cases). Interestingly, this test doesn't actually
detect the bug, because it is running "git gc", and not "prune"
directly. And "gc" will call "repack" first, which does not suffer the
same bug. So the old-but-reachable-from-recent objects get scooped up
into the new pack along with the actually-recent objects, which gives
both a recent mtime. But it seemed prudent to get more coverage of the
bitmap case for related code.
Reported-by: David Emett <dave@sp4m.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-04-28 15:42:43 +00:00
|
|
|
;;
|
|
|
|
bitmap)
|
|
|
|
git repack -adb
|
|
|
|
;;
|
|
|
|
*)
|
|
|
|
echo >&2 "unknown test type in maybe_repack"
|
|
|
|
return 1
|
|
|
|
;;
|
|
|
|
esac
|
2014-10-15 22:42:09 +00:00
|
|
|
}
|
|
|
|
|
prune: save reachable-from-recent objects with bitmaps
We pass our prune expiration to mark_reachable_objects(), which will
traverse not only the reachable objects, but consider any recent ones as
tips for reachability; see d3038d22f9 (prune: keep objects reachable
from recent objects, 2014-10-15) for details.
However, this interacts badly with the bitmap code path added in
fde67d6896 (prune: use bitmaps for reachability traversal, 2019-02-13).
If we hit the bitmap-optimized path, we return immediately to avoid the
regular traversal, accidentally skipping the "also traverse recent"
code.
Instead, we should do an if-else for the bitmap versus regular
traversal, and then follow up with the "recent" traversal in either
case. This reuses the "rev_info" for a bitmap and then a regular
traversal, but that should work OK (the bitmap code clears the pending
array in the usual way, just like a regular traversal would).
Note that I dropped the comment above the regular traversal here. It
has little explanatory value, and makes the if-else logic much harder to
read.
Here are a few variants that I rejected:
- it seems like both the reachability and recent traversals could be
done in a single traversal. This was rejected by d3038d22f9 (prune:
keep objects reachable from recent objects, 2014-10-15), though the
balance may be different when using bitmaps. However, there's a
subtle correctness issue, too: we use revs->ignore_missing_links for
the recent traversal, but not the reachability one.
- we could try using bitmaps for the recent traversal, too, which
could possibly improve performance. But it would require some fixes
in the bitmap code, which uses ignore_missing_links for its own
purposes. Plus it would probably not help all that much in practice.
We use the reachable tips to generate bitmaps, so those objects are
likely not covered by bitmaps (unless they just became unreachable).
And in general, we expect the set of unreachable objects to be much
smaller anyway, so there's less to gain.
The test in t5304 detects the bug and confirms the fix.
I also beefed up the tests in t6501, which covers the mtime-checking
code more thoroughly, to handle the bitmap case (in addition to just
"loose" and "packed" cases). Interestingly, this test doesn't actually
detect the bug, because it is running "git gc", and not "prune"
directly. And "gc" will call "repack" first, which does not suffer the
same bug. So the old-but-reachable-from-recent objects get scooped up
into the new pack along with the actually-recent objects, which gives
both a recent mtime. But it seemed prudent to get more coverage of the
bitmap case for related code.
Reported-by: David Emett <dave@sp4m.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-04-28 15:42:43 +00:00
|
|
|
for title in loose repack bitmap
|
|
|
|
do
|
2014-10-15 22:42:09 +00:00
|
|
|
test_expect_success "make repo completely empty ($title)" '
|
|
|
|
rm -rf .git &&
|
|
|
|
git init
|
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success "disable reflogs ($title)" '
|
|
|
|
git config core.logallrefupdates false &&
|
2015-07-27 22:57:08 +00:00
|
|
|
git reflog expire --expire=all --all
|
2014-10-15 22:42:09 +00:00
|
|
|
'
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
|
2014-10-15 22:42:09 +00:00
|
|
|
test_expect_success "setup basic history ($title)" '
|
|
|
|
commit base
|
|
|
|
'
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
|
2014-10-15 22:42:09 +00:00
|
|
|
test_expect_success "create and abandon some objects ($title)" '
|
|
|
|
git checkout -b experiment &&
|
|
|
|
commit abandon &&
|
|
|
|
maybe_repack &&
|
2020-11-18 23:44:38 +00:00
|
|
|
git checkout main &&
|
2014-10-15 22:42:09 +00:00
|
|
|
git branch -D experiment
|
|
|
|
'
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
|
2014-10-15 22:42:09 +00:00
|
|
|
test_expect_success "simulate time passing ($title)" '
|
2018-04-25 04:29:00 +00:00
|
|
|
test-tool chmtime --get -86400 $(find .git/objects -type f)
|
2014-10-15 22:42:09 +00:00
|
|
|
'
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
|
2014-10-15 22:42:09 +00:00
|
|
|
test_expect_success "start writing new commit with old blob ($title)" '
|
|
|
|
tree=$(
|
|
|
|
GIT_INDEX_FILE=index.tmp &&
|
|
|
|
export GIT_INDEX_FILE &&
|
|
|
|
git read-tree HEAD &&
|
|
|
|
add unrelated &&
|
|
|
|
add abandon &&
|
|
|
|
git write-tree
|
|
|
|
)
|
|
|
|
'
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
|
2014-10-15 22:42:09 +00:00
|
|
|
test_expect_success "simultaneous gc ($title)" '
|
|
|
|
git gc --prune=12.hours.ago
|
|
|
|
'
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
|
2014-10-15 22:42:09 +00:00
|
|
|
test_expect_success "finish writing out commit ($title)" '
|
|
|
|
commit=$(echo foo | git commit-tree -p HEAD $tree) &&
|
|
|
|
git update-ref HEAD $commit
|
|
|
|
'
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
|
2014-10-15 22:42:09 +00:00
|
|
|
# "abandon" blob should have been rescued by reference from new tree
|
|
|
|
test_expect_success "repository passes fsck ($title)" '
|
|
|
|
git fsck
|
|
|
|
'
|
2014-10-15 22:42:22 +00:00
|
|
|
|
|
|
|
test_expect_success "abandon objects again ($title)" '
|
|
|
|
git reset --hard HEAD^ &&
|
2018-04-25 04:29:00 +00:00
|
|
|
test-tool chmtime --get -86400 $(find .git/objects -type f)
|
2014-10-15 22:42:22 +00:00
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success "start writing new commit with same tree ($title)" '
|
|
|
|
tree=$(
|
|
|
|
GIT_INDEX_FILE=index.tmp &&
|
|
|
|
export GIT_INDEX_FILE &&
|
|
|
|
git read-tree HEAD &&
|
|
|
|
add abandon &&
|
|
|
|
add unrelated &&
|
|
|
|
git write-tree
|
|
|
|
)
|
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success "simultaneous gc ($title)" '
|
|
|
|
git gc --prune=12.hours.ago
|
|
|
|
'
|
|
|
|
|
|
|
|
# tree should have been refreshed by write-tree
|
|
|
|
test_expect_success "finish writing out commit ($title)" '
|
|
|
|
commit=$(echo foo | git commit-tree -p HEAD $tree) &&
|
|
|
|
git update-ref HEAD $commit
|
|
|
|
'
|
2014-10-15 22:42:09 +00:00
|
|
|
done
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
|
2017-05-20 08:30:25 +00:00
|
|
|
test_expect_success 'do not complain about existing broken links (commit)' '
|
2020-07-29 23:13:58 +00:00
|
|
|
cat >broken-commit <<-EOF &&
|
|
|
|
tree $(test_oid 001)
|
|
|
|
parent $(test_oid 002)
|
2015-06-01 09:56:37 +00:00
|
|
|
author whatever <whatever@example.com> 1234 -0000
|
|
|
|
committer whatever <whatever@example.com> 1234 -0000
|
|
|
|
|
|
|
|
some message
|
|
|
|
EOF
|
|
|
|
commit=$(git hash-object -t commit -w broken-commit) &&
|
2019-08-13 18:37:45 +00:00
|
|
|
git gc -q 2>stderr &&
|
2015-06-01 09:56:37 +00:00
|
|
|
verbose git cat-file -e $commit &&
|
|
|
|
test_must_be_empty stderr
|
|
|
|
'
|
|
|
|
|
2017-05-20 08:30:25 +00:00
|
|
|
test_expect_success 'do not complain about existing broken links (tree)' '
|
2020-07-29 23:13:58 +00:00
|
|
|
cat >broken-tree <<-EOF &&
|
|
|
|
100644 blob $(test_oid 003) foo
|
2017-05-20 08:30:25 +00:00
|
|
|
EOF
|
|
|
|
tree=$(git mktree --missing <broken-tree) &&
|
2019-08-13 18:37:45 +00:00
|
|
|
git gc -q 2>stderr &&
|
2017-05-20 08:30:25 +00:00
|
|
|
git cat-file -e $tree &&
|
|
|
|
test_must_be_empty stderr
|
|
|
|
'
|
|
|
|
|
|
|
|
test_expect_success 'do not complain about existing broken links (tag)' '
|
2020-07-29 23:13:58 +00:00
|
|
|
cat >broken-tag <<-EOF &&
|
|
|
|
object $(test_oid 004)
|
2017-05-20 08:30:25 +00:00
|
|
|
type commit
|
|
|
|
tag broken
|
|
|
|
tagger whatever <whatever@example.com> 1234 -0000
|
|
|
|
|
|
|
|
this is a broken tag
|
|
|
|
EOF
|
|
|
|
tag=$(git hash-object -t tag -w broken-tag) &&
|
2019-08-13 18:37:45 +00:00
|
|
|
git gc -q 2>stderr &&
|
2017-05-20 08:30:25 +00:00
|
|
|
git cat-file -e $tag &&
|
|
|
|
test_must_be_empty stderr
|
|
|
|
'
|
|
|
|
|
prune: keep objects reachable from recent objects
Our current strategy with prune is that an object falls into
one of three categories:
1. Reachable (from ref tips, reflogs, index, etc).
2. Not reachable, but recent (based on the --expire time).
3. Not reachable and not recent.
We keep objects from (1) and (2), but prune objects in (3).
The point of (2) is that these objects may be part of an
in-progress operation that has not yet updated any refs.
However, it is not always the case that objects for an
in-progress operation will have a recent mtime. For example,
the object database may have an old copy of a blob (from an
abandoned operation, a branch that was deleted, etc). If we
create a new tree that points to it, a simultaneous prune
will leave our tree, but delete the blob. Referencing that
tree with a commit will then work (we check that the tree is
in the object database, but not that all of its referred
objects are), as will mentioning the commit in a ref. But
the resulting repo is corrupt; we are missing the blob
reachable from a ref.
One way to solve this is to be more thorough when
referencing a sha1: make sure that not only do we have that
sha1, but that we have objects it refers to, and so forth
recursively. The problem is that this is very expensive.
Creating a parent link would require traversing the entire
object graph!
Instead, this patch pushes the extra work onto prune, which
runs less frequently (and has to look at the whole object
graph anyway). It creates a new category of objects: objects
which are not recent, but which are reachable from a recent
object. We do not prune these objects, just like the
reachable and recent ones.
This lets us avoid the recursive check above, because if we
have an object, even if it is unreachable, we should have
its referent. We can make a simple inductive argument that
with this patch, this property holds (that there are no
objects with missing referents in the repository):
0. When we have no objects, we have nothing to refer or be
referred to, so the property holds.
1. If we add objects to the repository, their direct
referents must generally exist (e.g., if you create a
tree, the blobs it references must exist; if you create
a commit to point at the tree, the tree must exist).
This is already the case before this patch. And it is
not 100% foolproof (you can make bogus objects using
`git hash-object`, for example), but it should be the
case for normal usage.
Therefore for any sequence of object additions, the
property will continue to hold.
2. If we remove objects from the repository, then we will
not remove a child object (like a blob) if an object
that refers to it is being kept. That is the part
implemented by this patch.
Note, however, that our reachability check and the
actual pruning are not atomic. So it _is_ still
possible to violate the property (e.g., an object
becomes referenced just as we are deleting it). This
patch is shooting for eliminating problems where the
mtimes of dependent objects differ by hours or days,
and one is dropped without the other. It does nothing
to help with short races.
Naively, the simplest way to implement this would be to add
all recent objects as tips to the reachability traversal.
However, this does not perform well. In a recently-packed
repository, all reachable objects will also be recent, and
therefore we have to look at each object twice. This patch
instead performs the reachability traversal, then follows up
with a second traversal for recent objects, skipping any
that have already been marked.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-15 22:41:35 +00:00
|
|
|
test_done
|