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git/t/t6600-test-reach.sh
Derrick Stolee 8791bf1841 commit-reach: fix in_merge_bases_many bug 
Way back in f9b8908b (commit.c: use generation numbers for
in_merge_bases(), 2018-05-01), a heuristic was used to short-circuit
the in_merge_bases() walk. This works just fine as long as the
caller is checking only two commits, but when there are multiple,
there is a possibility that this heuristic is _very wrong_.

Some code moves since then has changed this method to
repo_in_merge_bases_many() inside commit-reach.c. The heuristic
computes the minimum generation number of the "reference" list, then
compares this number to the generation number of the "commit".

In a recent topic, a test was added that used in_merge_bases_many()
to test if a commit was reachable from a number of commits pulled
from a reflog. However, this highlighted the problem: if any of the
reference commits have a smaller generation number than the given
commit, then the walk is skipped _even if there exist some with
higher generation number_.

This heuristic is wrong! It must check the MAXIMUM generation number
of the reference commits, not the MINIMUM.

This highlights a testing gap. t6600-test-reach.sh covers many
methods in commit-reach.c, including in_merge_bases() and
get_merge_bases_many(), but since these methods either restrict to
two input commits or actually look for the full list of merge bases,
they don't check this heuristic!

Add a possible input to "test-tool reach" that tests
in_merge_bases_many() and add tests to t6600-test-reach.sh that
cover this heuristic. This includes cases for the reference commits
having generation above and below the generation of the input commit,
but also having maximum generation below the generation of the input
commit.

The fix itself is to swap min_generation with a max_generation in
repo_in_merge_bases_many().

Reported-by: Srinidhi Kaushik <shrinidhi.kaushik@gmail.com>
Helped-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-10-02 10:26:31 -07:00

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#!/bin/sh
test_description='basic commit reachability tests'
. ./test-lib.sh
# Construct a grid-like commit graph with points (x,y)
# with 1 <= x <= 10, 1 <= y <= 10, where (x,y) has
# parents (x-1, y) and (x, y-1), keeping in mind that
# we drop a parent if a coordinate is nonpositive.
#
# (10,10)
# / \
# (10,9) (9,10)
# / \ / \
# (10,8) (9,9) (8,10)
# / \ / \ / \
# ( continued...)
# \ / \ / \ /
# (3,1) (2,2) (1,3)
# \ / \ /
# (2,1) (2,1)
# \ /
# (1,1)
#
# We use branch 'commit-x-y' to refer to (x,y).
# This grid allows interesting reachability and
# non-reachability queries: (x,y) can reach (x',y')
# if and only if x' <= x and y' <= y.
test_expect_success 'setup' '
for i in $(test_seq 1 10)
do
test_commit "1-$i" &&
git branch -f commit-1-$i &&
git tag -a -m "1-$i" tag-1-$i commit-1-$i
done &&
for j in $(test_seq 1 9)
do
git reset --hard commit-$j-1 &&
x=$(($j + 1)) &&
test_commit "$x-1" &&
git branch -f commit-$x-1 &&
git tag -a -m "$x-1" tag-$x-1 commit-$x-1 &&
for i in $(test_seq 2 10)
do
git merge commit-$j-$i -m "$x-$i" &&
git branch -f commit-$x-$i &&
git tag -a -m "$x-$i" tag-$x-$i commit-$x-$i
done
done &&
git commit-graph write --reachable &&
mv .git/objects/info/commit-graph commit-graph-full &&
chmod u+w commit-graph-full &&
git show-ref -s commit-5-5 | git commit-graph write --stdin-commits &&
mv .git/objects/info/commit-graph commit-graph-half &&
chmod u+w commit-graph-half &&
git config core.commitGraph true
'
run_three_modes () {
test_when_finished rm -rf .git/objects/info/commit-graph &&
"$@" <input >actual &&
test_cmp expect actual &&
cp commit-graph-full .git/objects/info/commit-graph &&
"$@" <input >actual &&
test_cmp expect actual &&
cp commit-graph-half .git/objects/info/commit-graph &&
"$@" <input >actual &&
test_cmp expect actual
}
test_three_modes () {
run_three_modes test-tool reach "$@"
}
test_expect_success 'ref_newer:miss' '
cat >input <<-\EOF &&
A:commit-5-7
B:commit-4-9
EOF
echo "ref_newer(A,B):0" >expect &&
test_three_modes ref_newer
'
test_expect_success 'ref_newer:hit' '
cat >input <<-\EOF &&
A:commit-5-7
B:commit-2-3
EOF
echo "ref_newer(A,B):1" >expect &&
test_three_modes ref_newer
'
test_expect_success 'in_merge_bases:hit' '
cat >input <<-\EOF &&
A:commit-5-7
B:commit-8-8
EOF
echo "in_merge_bases(A,B):1" >expect &&
test_three_modes in_merge_bases
'
test_expect_success 'in_merge_bases:miss' '
cat >input <<-\EOF &&
A:commit-6-8
B:commit-5-9
EOF
echo "in_merge_bases(A,B):0" >expect &&
test_three_modes in_merge_bases
'
test_expect_success 'in_merge_bases_many:hit' '
cat >input <<-\EOF &&
A:commit-6-8
X:commit-6-9
X:commit-5-7
EOF
echo "in_merge_bases_many(A,X):1" >expect &&
test_three_modes in_merge_bases_many
'
test_expect_success 'in_merge_bases_many:miss' '
cat >input <<-\EOF &&
A:commit-6-8
X:commit-7-7
X:commit-8-6
EOF
echo "in_merge_bases_many(A,X):0" >expect &&
test_three_modes in_merge_bases_many
'
test_expect_success 'in_merge_bases_many:miss-heuristic' '
cat >input <<-\EOF &&
A:commit-6-8
X:commit-7-5
X:commit-6-6
EOF
echo "in_merge_bases_many(A,X):0" >expect &&
test_three_modes in_merge_bases_many
'
test_expect_success 'is_descendant_of:hit' '
cat >input <<-\EOF &&
A:commit-5-7
X:commit-4-8
X:commit-6-6
X:commit-1-1
EOF
echo "is_descendant_of(A,X):1" >expect &&
test_three_modes is_descendant_of
'
test_expect_success 'is_descendant_of:miss' '
cat >input <<-\EOF &&
A:commit-6-8
X:commit-5-9
X:commit-4-10
X:commit-7-6
EOF
echo "is_descendant_of(A,X):0" >expect &&
test_three_modes is_descendant_of
'
test_expect_success 'get_merge_bases_many' '
cat >input <<-\EOF &&
A:commit-5-7
X:commit-4-8
X:commit-6-6
X:commit-8-3
EOF
{
echo "get_merge_bases_many(A,X):" &&
git rev-parse commit-5-6 \
commit-4-7 | sort
} >expect &&
test_three_modes get_merge_bases_many
'
test_expect_success 'reduce_heads' '
cat >input <<-\EOF &&
X:commit-1-10
X:commit-2-8
X:commit-3-6
X:commit-4-4
X:commit-1-7
X:commit-2-5
X:commit-3-3
X:commit-5-1
EOF
{
echo "reduce_heads(X):" &&
git rev-parse commit-5-1 \
commit-4-4 \
commit-3-6 \
commit-2-8 \
commit-1-10 | sort
} >expect &&
test_three_modes reduce_heads
'
test_expect_success 'can_all_from_reach:hit' '
cat >input <<-\EOF &&
X:commit-2-10
X:commit-3-9
X:commit-4-8
X:commit-5-7
X:commit-6-6
X:commit-7-5
X:commit-8-4
X:commit-9-3
Y:commit-1-9
Y:commit-2-8
Y:commit-3-7
Y:commit-4-6
Y:commit-5-5
Y:commit-6-4
Y:commit-7-3
Y:commit-8-1
EOF
echo "can_all_from_reach(X,Y):1" >expect &&
test_three_modes can_all_from_reach
'
test_expect_success 'can_all_from_reach:miss' '
cat >input <<-\EOF &&
X:commit-2-10
X:commit-3-9
X:commit-4-8
X:commit-5-7
X:commit-6-6
X:commit-7-5
X:commit-8-4
X:commit-9-3
Y:commit-1-9
Y:commit-2-8
Y:commit-3-7
Y:commit-4-6
Y:commit-5-5
Y:commit-6-4
Y:commit-8-5
EOF
echo "can_all_from_reach(X,Y):0" >expect &&
test_three_modes can_all_from_reach
'
test_expect_success 'can_all_from_reach_with_flag: tags case' '
cat >input <<-\EOF &&
X:tag-2-10
X:tag-3-9
X:tag-4-8
X:commit-5-7
X:commit-6-6
X:commit-7-5
X:commit-8-4
X:commit-9-3
Y:tag-1-9
Y:tag-2-8
Y:tag-3-7
Y:commit-4-6
Y:commit-5-5
Y:commit-6-4
Y:commit-7-3
Y:commit-8-1
EOF
echo "can_all_from_reach_with_flag(X,_,_,0,0):1" >expect &&
test_three_modes can_all_from_reach_with_flag
'
test_expect_success 'commit_contains:hit' '
cat >input <<-\EOF &&
A:commit-7-7
X:commit-2-10
X:commit-3-9
X:commit-4-8
X:commit-5-7
X:commit-6-6
X:commit-7-5
X:commit-8-4
X:commit-9-3
EOF
echo "commit_contains(_,A,X,_):1" >expect &&
test_three_modes commit_contains &&
test_three_modes commit_contains --tag
'
test_expect_success 'commit_contains:miss' '
cat >input <<-\EOF &&
A:commit-6-5
X:commit-2-10
X:commit-3-9
X:commit-4-8
X:commit-5-7
X:commit-6-6
X:commit-7-5
X:commit-8-4
X:commit-9-3
EOF
echo "commit_contains(_,A,X,_):0" >expect &&
test_three_modes commit_contains &&
test_three_modes commit_contains --tag
'
test_expect_success 'rev-list: basic topo-order' '
git rev-parse \
commit-6-6 commit-5-6 commit-4-6 commit-3-6 commit-2-6 commit-1-6 \
commit-6-5 commit-5-5 commit-4-5 commit-3-5 commit-2-5 commit-1-5 \
commit-6-4 commit-5-4 commit-4-4 commit-3-4 commit-2-4 commit-1-4 \
commit-6-3 commit-5-3 commit-4-3 commit-3-3 commit-2-3 commit-1-3 \
commit-6-2 commit-5-2 commit-4-2 commit-3-2 commit-2-2 commit-1-2 \
commit-6-1 commit-5-1 commit-4-1 commit-3-1 commit-2-1 commit-1-1 \
>expect &&
run_three_modes git rev-list --topo-order commit-6-6
'
test_expect_success 'rev-list: first-parent topo-order' '
git rev-parse \
commit-6-6 \
commit-6-5 \
commit-6-4 \
commit-6-3 \
commit-6-2 \
commit-6-1 commit-5-1 commit-4-1 commit-3-1 commit-2-1 commit-1-1 \
>expect &&
run_three_modes git rev-list --first-parent --topo-order commit-6-6
'
test_expect_success 'rev-list: range topo-order' '
git rev-parse \
commit-6-6 commit-5-6 commit-4-6 commit-3-6 commit-2-6 commit-1-6 \
commit-6-5 commit-5-5 commit-4-5 commit-3-5 commit-2-5 commit-1-5 \
commit-6-4 commit-5-4 commit-4-4 commit-3-4 commit-2-4 commit-1-4 \
commit-6-3 commit-5-3 commit-4-3 \
commit-6-2 commit-5-2 commit-4-2 \
commit-6-1 commit-5-1 commit-4-1 \
>expect &&
run_three_modes git rev-list --topo-order commit-3-3..commit-6-6
'
test_expect_success 'rev-list: range topo-order' '
git rev-parse \
commit-6-6 commit-5-6 commit-4-6 \
commit-6-5 commit-5-5 commit-4-5 \
commit-6-4 commit-5-4 commit-4-4 \
commit-6-3 commit-5-3 commit-4-3 \
commit-6-2 commit-5-2 commit-4-2 \
commit-6-1 commit-5-1 commit-4-1 \
>expect &&
run_three_modes git rev-list --topo-order commit-3-8..commit-6-6
'
test_expect_success 'rev-list: first-parent range topo-order' '
git rev-parse \
commit-6-6 \
commit-6-5 \
commit-6-4 \
commit-6-3 \
commit-6-2 \
commit-6-1 commit-5-1 commit-4-1 \
>expect &&
run_three_modes git rev-list --first-parent --topo-order commit-3-8..commit-6-6
'
test_expect_success 'rev-list: ancestry-path topo-order' '
git rev-parse \
commit-6-6 commit-5-6 commit-4-6 commit-3-6 \
commit-6-5 commit-5-5 commit-4-5 commit-3-5 \
commit-6-4 commit-5-4 commit-4-4 commit-3-4 \
commit-6-3 commit-5-3 commit-4-3 \
>expect &&
run_three_modes git rev-list --topo-order --ancestry-path commit-3-3..commit-6-6
'
test_expect_success 'rev-list: symmetric difference topo-order' '
git rev-parse \
commit-6-6 commit-5-6 commit-4-6 \
commit-6-5 commit-5-5 commit-4-5 \
commit-6-4 commit-5-4 commit-4-4 \
commit-6-3 commit-5-3 commit-4-3 \
commit-6-2 commit-5-2 commit-4-2 \
commit-6-1 commit-5-1 commit-4-1 \
commit-3-8 commit-2-8 commit-1-8 \
commit-3-7 commit-2-7 commit-1-7 \
>expect &&
run_three_modes git rev-list --topo-order commit-3-8...commit-6-6
'
test_expect_success 'get_reachable_subset:all' '
cat >input <<-\EOF &&
X:commit-9-1
X:commit-8-3
X:commit-7-5
X:commit-6-6
X:commit-1-7
Y:commit-3-3
Y:commit-1-7
Y:commit-5-6
EOF
(
echo "get_reachable_subset(X,Y)" &&
git rev-parse commit-3-3 \
commit-1-7 \
commit-5-6 | sort
) >expect &&
test_three_modes get_reachable_subset
'
test_expect_success 'get_reachable_subset:some' '
cat >input <<-\EOF &&
X:commit-9-1
X:commit-8-3
X:commit-7-5
X:commit-1-7
Y:commit-3-3
Y:commit-1-7
Y:commit-5-6
EOF
(
echo "get_reachable_subset(X,Y)" &&
git rev-parse commit-3-3 \
commit-1-7 | sort
) >expect &&
test_three_modes get_reachable_subset
'
test_expect_success 'get_reachable_subset:none' '
cat >input <<-\EOF &&
X:commit-9-1
X:commit-8-3
X:commit-7-5
X:commit-1-7
Y:commit-9-3
Y:commit-7-6
Y:commit-2-8
EOF
echo "get_reachable_subset(X,Y)" >expect &&
test_three_modes get_reachable_subset
'
test_done
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