1 files changed, 182 insertions, 0 deletions
diff --git a/t/t4051-diff-function-context.sh b/t/t4051-diff-function-context.sh
new file mode 100755
index 0000000000..b79b87790b
--- /dev/null
+++ b/t/t4051-diff-function-context.sh
@@ -0,0 +1,182 @@
+#!/bin/sh
+
+test_description='diff function context'
+
+. ./test-lib.sh
+
+dir="$TEST_DIRECTORY/t4051"
+
+commit_and_tag () {
+	tag=$1 &&
+	shift &&
+	git add "$@" &&
+	test_tick &&
+	git commit -m "$tag" &&
+	git tag "$tag"
+}
+
+first_context_line () {
+	awk '
+		found {print; exit}
+		/^@@/ {found = 1}
+	'
+}
+
+last_context_line () {
+	sed -ne \$p
+}
+
+check_diff () {
+	name=$1
+	desc=$2
+	options="-W $3"
+
+	test_expect_success "$desc" '
+		git diff $options "$name^" "$name" >"$name.diff"
+	'
+
+	test_expect_success ' diff applies' '
+		test_when_finished "git reset --hard" &&
+		git checkout --detach "$name^" &&
+		git apply --index "$name.diff" &&
+		git diff --exit-code "$name"
+	'
+}
+
+test_expect_success 'setup' '
+	cat "$dir/includes.c" "$dir/dummy.c" "$dir/dummy.c" "$dir/hello.c" \
+		"$dir/dummy.c" "$dir/dummy.c" >file.c &&
+	commit_and_tag initial file.c &&
+
+	grep -v "delete me from hello" <file.c >file.c.new &&
+	mv file.c.new file.c &&
+	commit_and_tag changed_hello file.c &&
+
+	grep -v "delete me from includes" <file.c >file.c.new &&
+	mv file.c.new file.c &&
+	commit_and_tag changed_includes file.c &&
+
+	cat "$dir/appended1.c" >>file.c &&
+	commit_and_tag appended file.c &&
+
+	cat "$dir/appended2.c" >>file.c &&
+	commit_and_tag extended file.c &&
+
+	grep -v "Begin of second part" <file.c >file.c.new &&
+	mv file.c.new file.c &&
+	commit_and_tag long_common_tail file.c &&
+
+	git checkout initial &&
+	grep -v "delete me from hello" <file.c >file.c.new &&
+	mv file.c.new file.c &&
+	cat "$dir/appended1.c" >>file.c &&
+	commit_and_tag changed_hello_appended file.c
+'
+
+check_diff changed_hello 'changed function'
+
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin of hello" changed_hello.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^ .*End of hello" changed_hello.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" changed_hello.diff) -le 1
+'
+
+test_expect_success ' context does not include preceding empty lines' '
+	test "$(first_context_line <changed_hello.diff)" != " "
+'
+
+test_expect_success ' context does not include trailing empty lines' '
+	test "$(last_context_line <changed_hello.diff)" != " "
+'
+
+check_diff changed_includes 'changed includes'
+
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin.h" changed_includes.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^ .*End.h" changed_includes.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" changed_includes.diff) -le 1
+'
+
+test_expect_success ' context does not include trailing empty lines' '
+	test "$(last_context_line <changed_includes.diff)" != " "
+'
+
+check_diff appended 'appended function'
+
+test_expect_success ' context includes begin' '
+	grep "^[+].*Begin of first part" appended.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^[+].*End of first part" appended.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" appended.diff) -le 1
+'
+
+check_diff extended 'appended function part'
+
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin of first part" extended.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^[+].*End of second part" extended.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" extended.diff) -le 2
+'
+
+test_expect_success ' context does not include preceding empty lines' '
+	test "$(first_context_line <extended.diff)" != " "
+'
+
+check_diff long_common_tail 'change with long common tail and no context' -U0
+
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin of first part" long_common_tail.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^ .*End of second part" long_common_tail.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" long_common_tail.diff) -le 2
+'
+
+test_expect_success ' context does not include preceding empty lines' '
+	test "$(first_context_line <long_common_tail.diff.diff)" != " "
+'
+
+check_diff changed_hello_appended 'changed function plus appended function'
+
+test_expect_success ' context includes begin' '
+	grep "^ .*Begin of hello" changed_hello_appended.diff &&
+	grep "^[+].*Begin of first part" changed_hello_appended.diff
+'
+
+test_expect_success ' context includes end' '
+	grep "^ .*End of hello" changed_hello_appended.diff &&
+	grep "^[+].*End of first part" changed_hello_appended.diff
+'
+
+test_expect_success ' context does not include other functions' '
+	test $(grep -c "^[ +-].*Begin" changed_hello_appended.diff) -le 2
+'
+
+test_done