fast-export: add support to delete refs

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fast-export.c

@@ -673,6 +673,19 @@ static void import_marks(char *input_file)
 	fclose(f);
 }
 
+static void handle_deletes(void)
+{
+	int i;
+	for (i = 0; i < refspecs_nr; i++) {
+		struct refspec *refspec = &refspecs[i];
+		if (*refspec->src)
+			continue;
+
+		printf("reset %s\nfrom %s\n\n",
+				refspec->dst, sha1_to_hex(null_sha1));
+	}
+}
+
 int cmd_fast_export(int argc, const char **argv, const char *prefix)
 {
 	struct rev_info revs;
@@ -764,6 +777,7 @@ int cmd_fast_export(int argc, const char **argv, const char *prefix)
 	}
 
 	handle_tags_and_duplicates();
+	handle_deletes();
 
 	if (export_filename && lastimportid != last_idnum)
 		export_marks(export_filename);

t/t9350-fast-export.sh

@@ -511,4 +511,15 @@ test_expect_success 'use refspec' '
 	test_cmp expected actual
 '
 
+test_expect_success 'delete refspec' '
+	git branch to-delete &&
+	git fast-export --refspec :refs/heads/to-delete to-delete ^to-delete > actual &&
+	cat > expected <<-EOF &&
+	reset refs/heads/to-delete
+	from 0000000000000000000000000000000000000000
+
+	EOF
+	test_cmp expected actual
+'
+
 test_done