t7519: rewrite sparse index test

The sparse index is tested with the FS Monitor hook and extension since
f8fe49e (fsmonitor: integrate with sparse index, 2021-07-14). This test
was very fragile because it shared an index across sparse and non-sparse
behavior. Since that expansion and contraction could cause the index to
lose its FS Monitor bitmap and token, behavior is fragile to changes in
'git sparse-checkout set'.

Rewrite the test to use two clones of the original repo: full and
sparse. This allows us to also keep the test files (actual, expect,
trace2.txt) out of the repos we are testing with 'git status'.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

Author: derrickstolee

t/t7519-status-fsmonitor.sh

@@ -389,43 +389,47 @@ test_expect_success 'status succeeds after staging/unstaging' '
 # If "!" is supplied, then we verify that we do not call ensure_full_index
 # during a call to 'git status'. Otherwise, we verify that we _do_ call it.
 check_sparse_index_behavior () {
-	git status --porcelain=v2 >expect &&
-	git sparse-checkout init --cone --sparse-index &&
-	git sparse-checkout set dir1 dir2 &&
+	git -C full status --porcelain=v2 >expect &&
 	GIT_TRACE2_EVENT="$(pwd)/trace2.txt" GIT_TRACE2_EVENT_NESTING=10 \
-		git status --porcelain=v2 >actual &&
+		git -C sparse status --porcelain=v2 >actual &&
 	test_region $1 index ensure_full_index trace2.txt &&
 	test_region fsm_hook query trace2.txt &&
 	test_cmp expect actual &&
-	rm trace2.txt &&
-	git sparse-checkout disable
+	rm trace2.txt
 }
 
 test_expect_success 'status succeeds with sparse index' '
-	git reset --hard &&
+	git clone . full &&
+	git clone --sparse . sparse &&
+	git -C sparse sparse-checkout init --cone --sparse-index &&
+	git -C sparse sparse-checkout set dir1 dir2 &&
 
-	test_config core.fsmonitor "$TEST_DIRECTORY/t7519/fsmonitor-all" &&
-	check_sparse_index_behavior ! &&
-
-	write_script .git/hooks/fsmonitor-test<<-\EOF &&
+	write_script .git/hooks/fsmonitor-test <<-\EOF &&
 		printf "last_update_token\0"
 	EOF
-	git config core.fsmonitor .git/hooks/fsmonitor-test &&
+	git -C full config core.fsmonitor ../.git/hooks/fsmonitor-test &&
+	git -C sparse config core.fsmonitor ../.git/hooks/fsmonitor-test &&
 	check_sparse_index_behavior ! &&
 
-	write_script .git/hooks/fsmonitor-test<<-\EOF &&
+	write_script .git/hooks/fsmonitor-test <<-\EOF &&
 		printf "last_update_token\0"
 		printf "dir1/modified\0"
 	EOF
 	check_sparse_index_behavior ! &&
 
-	cp -r dir1 dir1a &&
-	git add dir1a &&
-	git commit -m "add dir1a" &&
+	git -C sparse sparse-checkout add dir1a &&
+
+	for repo in full sparse
+	do
+		cp -r $repo/dir1 $repo/dir1a &&
+		git -C $repo add dir1a &&
+		git -C $repo commit -m "add dir1a" || return 1
+	done &&
+	git -C sparse sparse-checkout set dir1 dir2 &&
 
 	# This one modifies outside the sparse-checkout definition
 	# and hence we expect to expand the sparse-index.
-	write_script .git/hooks/fsmonitor-test<<-\EOF &&
+	write_script .git/hooks/fsmonitor-test <<-\EOF &&
 		printf "last_update_token\0"
 		printf "dir1a/modified\0"
 	EOF