ref-filter: add ref_format_clear() function

After using the ref-filter API, callers should use ref_filter_clear() to
free any used memory. However, there's not a matching function to clear
the ref_format struct.

Traditionally this did not need to be cleaned up, as it was just a way
for the caller to store and pass format options as a single unit. Even
though the parsing step of some placeholders may allocate data, that's
usually inside their "used_atom" structs, which are part of the
ref_filter itself.

But a few placeholders keep data outside of there. The %(ahead-behind)
and %(is-base) parsers both keep a master list of bases, because they
perform a single filtering pass outside of the use of any particular
atom. And since the format parser does not have access to the ref_filter
struct, they store their cross-atom data in the ref_format struct
itself.

And thus when they are finished, the ref_format also needs to be cleaned
up. So let's add a function to do so, and call it from all of the users
of the ref-filter API.

The %(is-base) case is found by running LSan on t6300. After this patch,
the script can now be marked leak-free.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/branch.c

@@ -878,6 +878,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		string_list_clear(&output, 0);
 		ref_sorting_release(sorting);
 		ref_filter_clear(&filter);
+		ref_format_clear(&format);
 		return 0;
 	} else if (edit_description) {
 		const char *branch_name;

builtin/for-each-ref.c

@@ -104,6 +104,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	filter_and_format_refs(&filter, flags, sorting, &format);
 
 	ref_filter_clear(&filter);
+	ref_format_clear(&format);
 	ref_sorting_release(sorting);
 	strvec_clear(&vec);
 	return 0;

builtin/tag.c

@@ -702,6 +702,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 cleanup:
 	ref_sorting_release(sorting);
 	ref_filter_clear(&filter);
+	ref_format_clear(&format);
 	strbuf_release(&buf);
 	strbuf_release(&ref);
 	strbuf_release(&reflog_msg);

builtin/verify-tag.c

@@ -65,5 +65,6 @@ int cmd_verify_tag(int argc, const char **argv, const char *prefix)
 		if (format.format)
 			pretty_print_ref(name, &oid, &format);
 	}
+	ref_format_clear(&format);
 	return had_error;
 }

ref-filter.c

@@ -3621,3 +3621,16 @@ void ref_filter_clear(struct ref_filter *filter)
 	free_commit_list(filter->unreachable_from);
 	ref_filter_init(filter);
 }
+
+void ref_format_init(struct ref_format *format)
+{
+	struct ref_format blank = REF_FORMAT_INIT;
+	memcpy(format, &blank, sizeof(blank));
+}
+
+void ref_format_clear(struct ref_format *format)
+{
+	string_list_clear(&format->bases, 0);
+	string_list_clear(&format->is_base_tips, 0);
+	ref_format_init(format);
+}

ref-filter.h

@@ -221,4 +221,7 @@ void filter_is_base(struct repository *r,
 void ref_filter_init(struct ref_filter *filter);
 void ref_filter_clear(struct ref_filter *filter);
 
+void ref_format_init(struct ref_format *format);
+void ref_format_clear(struct ref_format *format);
+
 #endif /*  REF_FILTER_H  */

t/t6300-for-each-ref.sh

@@ -5,6 +5,7 @@
 
 test_description='for-each-ref test'
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 GNUPGHOME_NOT_USED=$GNUPGHOME
 . "$TEST_DIRECTORY"/lib-gpg.sh