[PATCH v4 17/19] parallel-checkout: add tests related to clone collisions

[Matheus Tavares <matheus.bernardino@usp.br>]

Add tests to confirm that path collisions are properly reported during a
clone operation using parallel-checkout.

Original-patch-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
---
 t/lib-parallel-checkout.sh              |  4 +-
 t/t2081-parallel-checkout-collisions.sh | 98 +++++++++++++++++++++++++
 2 files changed, 100 insertions(+), 2 deletions(-)
 create mode 100755 t/t2081-parallel-checkout-collisions.sh

diff --git a/t/lib-parallel-checkout.sh b/t/lib-parallel-checkout.sh
index 4dad9043fb..e62a433eb1 100644
--- a/t/lib-parallel-checkout.sh
+++ b/t/lib-parallel-checkout.sh
@@ -18,7 +18,7 @@ git_pc()
 		-c checkout.workers=$workers \
 		-c checkout.thresholdForParallelism=$threshold \
 		-c advice.detachedHead=0 \
-		"$@" &&
+		"$@" 2>&8 &&
 
 	# Check that the expected number of workers has been used. Note that it
 	# can be different from the requested number in two cases: when the
@@ -28,7 +28,7 @@ git_pc()
 	local workers_in_trace=$(grep "child_start\[..*\] git checkout--helper" trace | wc -l) &&
 	test $workers_in_trace -eq $expected_workers &&
 	rm -f trace
-}
+} 8>&2 2>&4
 
 # Verify that both the working tree and the index were created correctly
 verify_checkout()
diff --git a/t/t2081-parallel-checkout-collisions.sh b/t/t2081-parallel-checkout-collisions.sh
new file mode 100755
index 0000000000..5cab2dcd2c
--- /dev/null
+++ b/t/t2081-parallel-checkout-collisions.sh
@@ -0,0 +1,98 @@
+#!/bin/sh
+
+test_description='parallel-checkout collisions
+
+When there are path collisions during a clone, Git should report a warning
+listing all of the colliding entries. The sequential code detects a collision
+by calling lstat() before trying to open(O_CREAT) the file. Then, to find the
+colliding pair of an item k, it searches cache_entry[0, k-1].
+
+This is not sufficient in parallel checkout since:
+
+- A colliding file may be created between the lstat() and open() calls;
+- A colliding entry might appear in the second half of the cache_entry array.
+
+The tests in this file make sure that the collision detection code is extended
+for parallel checkout.
+'
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY/lib-parallel-checkout.sh"
+
+TEST_ROOT="$PWD"
+
+test_expect_success CASE_INSENSITIVE_FS 'setup' '
+	file_x_hex=$(git hash-object -w --stdin </dev/null) &&
+	file_x_oct=$(echo $file_x_hex | hex2oct) &&
+
+	attr_hex=$(echo "file_x filter=logger" | git hash-object -w --stdin) &&
+	attr_oct=$(echo $attr_hex | hex2oct) &&
+
+	printf "100644 FILE_X\0${file_x_oct}" >tree &&
+	printf "100644 FILE_x\0${file_x_oct}" >>tree &&
+	printf "100644 file_X\0${file_x_oct}" >>tree &&
+	printf "100644 file_x\0${file_x_oct}" >>tree &&
+	printf "100644 .gitattributes\0${attr_oct}" >>tree &&
+
+	tree_hex=$(git hash-object -w -t tree --stdin <tree) &&
+	commit_hex=$(git commit-tree -m collisions $tree_hex) &&
+	git update-ref refs/heads/collisions $commit_hex &&
+
+	write_script "$TEST_ROOT"/logger_script <<-\EOF
+	echo "$@" >>filter.log
+	EOF
+'
+
+for mode in parallel sequential-fallback
+do
+
+	case $mode in
+	parallel)		workers=2 threshold=0 expected_workers=2 ;;
+	sequential-fallback)	workers=2 threshold=100 expected_workers=0 ;;
+	esac
+
+	test_expect_success CASE_INSENSITIVE_FS "collision detection on $mode clone" '
+		git_pc $workers $threshold $expected_workers \
+			clone --branch=collisions . $mode 2>$mode.stderr &&
+
+		grep FILE_X $mode.stderr &&
+		grep FILE_x $mode.stderr &&
+		grep file_X $mode.stderr &&
+		grep file_x $mode.stderr &&
+		test_i18ngrep "the following paths have collided" $mode.stderr
+	'
+
+	# The following test ensures that the collision detection code is
+	# correctly looking for colliding peers in the second half of the
+	# cache_entry array. This is done by defining a smudge command for the
+	# *last* array entry, which makes it non-eligible for parallel-checkout.
+	# The last entry is then checked out *before* any worker is spawned,
+	# making it succeed and the workers' entries collide.
+	#
+	# Note: this test don't work on Windows because, on this system,
+	# collision detection uses strcmp() when core.ignoreCase=false. And we
+	# have to set core.ignoreCase=false so that only 'file_x' matches the
+	# pattern of the filter attribute. But it works on OSX, where collision
+	# detection uses inode.
+	#
+	test_expect_success CASE_INSENSITIVE_FS,!MINGW,!CYGWIN "collision detection on $mode clone w/ filter" '
+		git_pc $workers $threshold $expected_workers \
+			-c core.ignoreCase=false \
+			-c filter.logger.smudge="\"$TEST_ROOT/logger_script\" %f" \
+			clone --branch=collisions . ${mode}_with_filter \
+			2>${mode}_with_filter.stderr &&
+
+		grep FILE_X ${mode}_with_filter.stderr &&
+		grep FILE_x ${mode}_with_filter.stderr &&
+		grep file_X ${mode}_with_filter.stderr &&
+		grep file_x ${mode}_with_filter.stderr &&
+		test_i18ngrep "the following paths have collided" ${mode}_with_filter.stderr &&
+
+		# Make sure only "file_x" was filtered
+		test_path_is_file ${mode}_with_filter/filter.log &&
+		echo file_x >expected.filter.log &&
+		test_cmp ${mode}_with_filter/filter.log expected.filter.log
+	'
+done
+
+test_done
-- 
2.28.0