[PATCH 05/20] userdiff tests: list builtin drivers via test-tool

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Change the userdiff test to list the builtin drivers via the
test-tool, using the new for_each_userdiff_driver() API function.

This gets rid of the need to modify this part of the test every time a
new pattern is added, see 2ff6c34612 (userdiff: support Bash,
2020-10-22) and 09dad9256a (userdiff: support Markdown, 2020-05-02)
for two recent examples.

I only need the "list-builtin-drivers "argument here, but let's add
"list-custom-drivers" and "list-drivers" too, just because it's easy.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 Makefile                 |  1 +
 t/helper/test-tool.c     |  1 +
 t/helper/test-tool.h     |  1 +
 t/helper/test-userdiff.c | 32 ++++++++++++++++++++++++++++++++
 t/t4018-diff-funcname.sh | 29 +++++------------------------
 5 files changed, 40 insertions(+), 24 deletions(-)
 create mode 100644 t/helper/test-userdiff.c

diff --git a/Makefile b/Makefile
index 5a239cac20..710a0deaed 100644
--- a/Makefile
+++ b/Makefile
@@ -741,6 +741,7 @@ TEST_BUILTINS_OBJS += test-submodule-nested-repo-config.o
 TEST_BUILTINS_OBJS += test-subprocess.o
 TEST_BUILTINS_OBJS += test-trace2.o
 TEST_BUILTINS_OBJS += test-urlmatch-normalization.o
+TEST_BUILTINS_OBJS += test-userdiff.o
 TEST_BUILTINS_OBJS += test-wildmatch.o
 TEST_BUILTINS_OBJS += test-windows-named-pipe.o
 TEST_BUILTINS_OBJS += test-write-cache.o
diff --git a/t/helper/test-tool.c b/t/helper/test-tool.c
index f97cd9f48a..dcb05ca6e5 100644
--- a/t/helper/test-tool.c
+++ b/t/helper/test-tool.c
@@ -71,6 +71,7 @@ static struct test_cmd cmds[] = {
 	{ "submodule-nested-repo-config", cmd__submodule_nested_repo_config },
 	{ "subprocess", cmd__subprocess },
 	{ "trace2", cmd__trace2 },
+	{ "userdiff", cmd__userdiff },
 	{ "urlmatch-normalization", cmd__urlmatch_normalization },
 	{ "xml-encode", cmd__xml_encode },
 	{ "wildmatch", cmd__wildmatch },
diff --git a/t/helper/test-tool.h b/t/helper/test-tool.h
index 28072c0ad5..589f2e8ac6 100644
--- a/t/helper/test-tool.h
+++ b/t/helper/test-tool.h
@@ -61,6 +61,7 @@ int cmd__submodule_config(int argc, const char **argv);
 int cmd__submodule_nested_repo_config(int argc, const char **argv);
 int cmd__subprocess(int argc, const char **argv);
 int cmd__trace2(int argc, const char **argv);
+int cmd__userdiff(int argc, const char **argv);
 int cmd__urlmatch_normalization(int argc, const char **argv);
 int cmd__xml_encode(int argc, const char **argv);
 int cmd__wildmatch(int argc, const char **argv);
diff --git a/t/helper/test-userdiff.c b/t/helper/test-userdiff.c
new file mode 100644
index 0000000000..80de456287
--- /dev/null
+++ b/t/helper/test-userdiff.c
@@ -0,0 +1,32 @@
+#include "test-tool.h"
+#include "cache.h"
+#include "userdiff.h"
+
+static int userdiff_list_builtin_drivers_cb(struct userdiff_driver *driver,
+					    enum userdiff_driver_type type,
+					    void *priv)
+{
+	puts(driver->name);
+	return 0;
+}
+
+static int list_what(enum userdiff_driver_type type)
+{
+	return for_each_userdiff_driver(userdiff_list_builtin_drivers_cb, type,
+					NULL);
+}
+
+int cmd__userdiff(int argc, const char **argv)
+{
+	if (argc != 2)
+		return 1;
+
+	if (!strcmp(argv[1], "list-drivers"))
+		return list_what(USERDIFF_DRIVER_TYPE_UNSPECIFIED);
+	else if (!strcmp(argv[1], "list-builtin-drivers"))
+		return list_what(USERDIFF_DRIVER_TYPE_BUILTIN);
+	else if (!strcmp(argv[1], "list-custom-drivers"))
+		return list_what(USERDIFF_DRIVER_TYPE_CUSTOM);
+	else
+		return error("unknown argument %s", argv[1]);
+}
diff --git a/t/t4018-diff-funcname.sh b/t/t4018-diff-funcname.sh
index cefe329aea..11ac648451 100755
--- a/t/t4018-diff-funcname.sh
+++ b/t/t4018-diff-funcname.sh
@@ -8,6 +8,10 @@ test_description='Test custom diff function name patterns'
 . ./test-lib.sh
 
 test_expect_success 'setup' '
+	test-tool userdiff list-builtin-drivers >builtin-drivers &&
+	test_file_not_empty builtin-drivers &&
+	builtin_drivers=$(cat builtin-drivers) &&
+
 	# a non-trivial custom pattern
 	git config diff.custom1.funcname "!static
 !String
@@ -26,30 +30,7 @@ test_expect_success 'setup' '
 '
 
 diffpatterns="
-	ada
-	bash
-	bibtex
-	cpp
-	csharp
-	css
-	dts
-	elixir
-	fortran
-	fountain
-	golang
-	html
-	java
-	markdown
-	matlab
-	objc
-	pascal
-	perl
-	php
-	python
-	ruby
-	rust
-	tex
-	default
+	$builtin_drivers
 	custom1
 	custom2
 	custom3
-- 
2.30.0.284.gd98b1dd5eaa7