Merge branch 'gt/t-hash-unit-test'

A pair of test helpers that essentially are unit tests on hash
algorithms have been rewritten using the unit-tests framework.

* gt/t-hash-unit-test:
  t/: migrate helper/test-{sha1, sha256} to unit-tests/t-hash
  strbuf: introduce strbuf_addstrings() to repeatedly add a string

strbuf.c

@@ -313,6 +313,15 @@ void strbuf_add(struct strbuf *sb, const void *data, size_t len)
 	strbuf_setlen(sb, sb->len + len);
 }
 
+void strbuf_addstrings(struct strbuf *sb, const char *s, size_t n)
+{
+	size_t len = strlen(s);
+
+	strbuf_grow(sb, st_mult(len, n));
+	for (size_t i = 0; i < n; i++)
+		strbuf_add(sb, s, len);
+}
+
 void strbuf_addbuf(struct strbuf *sb, const struct strbuf *sb2)
 {
 	strbuf_grow(sb, sb2->len);