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116 lines
4.5 KiB
116 lines
4.5 KiB
From 51441e6460b505c07b4a8a6deeaa7de4bf6e8e33 Mon Sep 17 00:00:00 2001
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From: Junio C Hamano <gitster@pobox.com>
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Date: Fri, 3 May 2024 08:34:27 -0700
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Subject: [PATCH] stop using HEAD for attributes in bare repository by default
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With 23865355 (attr: read attributes from HEAD when bare repo,
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2023-10-13), we started to use the HEAD tree as the default
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attribute source in a bare repository. One argument for such a
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behaviour is that it would make things like "git archive" run in
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bare and non-bare repositories for the same commit consistent.
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This changes was merged to Git 2.43 but without an explicit mention
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in its release notes.
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It turns out that this change destroys performance of shallowly
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cloning from a bare repository. As the "server" installations are
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expected to be mostly bare, and "git pack-objects", which is the
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core of driving the other side of "git clone" and "git fetch" wants
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to see if a path is set not to delta with blobs from other paths via
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the attribute system, the change forces the server side to traverse
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the tree of the HEAD commit needlessly to find if each and every
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paths the objects it sends out has the attribute that controls the
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deltification. Given that (1) most projects do not configure such
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an attribute, and (2) it is dubious for the server side to honor
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such an end-user supplied attribute anyway, this was a poor choice
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of the default.
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To mitigate the current situation, let's revert the change that uses
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the tree of HEAD in a bare repository by default as the attribute
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source. This will help most people who have been happy with the
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behaviour of Git 2.42 and before.
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Two things to note:
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* If you are stuck with versions of Git 2.43 or newer, that is
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older than the release this fix appears in, you can explicitly
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set the attr.tree configuration variable to point at an empty
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tree object, i.e.
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$ git config attr.tree 4b825dc642cb6eb9a060e54bf8d69288fbee4904
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* If you like the behaviour we are reverting, you can explicitly
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set the attr.tree configuration variable to HEAD, i.e.
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$ git config attr.tree HEAD
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The right fix for this is to optimize the code paths that allow
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accesses to attributes in tree objects, but that is a much more
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involved change and is left as a longer-term project, outside the
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scope of this "first step" fix.
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Signed-off-by: Junio C Hamano <gitster@pobox.com>
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---
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attr.c | 7 -------
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t/t0003-attributes.sh | 10 ++++++++--
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t/t5001-archive-attr.sh | 3 ++-
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3 files changed, 10 insertions(+), 10 deletions(-)
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diff --git a/attr.c b/attr.c
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index e62876dfd3e9be..02ab8436266289 100644
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--- a/attr.c
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+++ b/attr.c
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@@ -1213,13 +1213,6 @@ static void compute_default_attr_source(struct object_id *attr_source)
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ignore_bad_attr_tree = 1;
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}
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- if (!default_attr_source_tree_object_name &&
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- startup_info->have_repository &&
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- is_bare_repository()) {
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- default_attr_source_tree_object_name = "HEAD";
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- ignore_bad_attr_tree = 1;
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- }
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-
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if (!default_attr_source_tree_object_name || !is_null_oid(attr_source))
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return;
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diff --git a/t/t0003-attributes.sh b/t/t0003-attributes.sh
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index aee2298f01331a..5de46ddf67f7ff 100755
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--- a/t/t0003-attributes.sh
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+++ b/t/t0003-attributes.sh
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@@ -384,13 +384,19 @@ test_expect_success 'bad attr source defaults to reading .gitattributes file' '
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)
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'
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-test_expect_success 'bare repo defaults to reading .gitattributes from HEAD' '
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+test_expect_success 'bare repo no longer defaults to reading .gitattributes from HEAD' '
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test_when_finished rm -rf test bare_with_gitattribute &&
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git init test &&
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test_commit -C test gitattributes .gitattributes "f/path test=val" &&
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git clone --bare test bare_with_gitattribute &&
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- echo "f/path: test: val" >expect &&
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+
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+ echo "f/path: test: unspecified" >expect &&
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git -C bare_with_gitattribute check-attr test -- f/path >actual &&
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+ test_cmp expect actual &&
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+
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+ echo "f/path: test: val" >expect &&
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+ git -C bare_with_gitattribute -c attr.tree=HEAD \
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+ check-attr test -- f/path >actual &&
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test_cmp expect actual
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'
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diff --git a/t/t5001-archive-attr.sh b/t/t5001-archive-attr.sh
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index eaf959d8f63f15..7310774af5efea 100755
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--- a/t/t5001-archive-attr.sh
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+++ b/t/t5001-archive-attr.sh
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@@ -133,7 +133,8 @@ test_expect_success 'git archive vs. bare' '
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'
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test_expect_success 'git archive with worktree attributes, bare' '
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- (cd bare && git archive --worktree-attributes HEAD) >bare-worktree.tar &&
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+ (cd bare &&
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+ git -c attr.tree=HEAD archive --worktree-attributes HEAD) >bare-worktree.tar &&
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(mkdir bare-worktree && cd bare-worktree && "$TAR" xf -) <bare-worktree.tar
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'
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