Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

t/helper/test-mergesort.c

@@ -0,0 +1,53 @@
+#include "test-tool.h"
+#include "cache.h"
+#include "mergesort.h"
+
+struct line {
+	char *text;
+	struct line *next;
+};
+
+static void *get_next(const void *a)
+{
+	return ((const struct line *)a)->next;
+}
+
+static void set_next(void *a, void *b)
+{
+	((struct line *)a)->next = b;
+}
+
+static int compare_strings(const void *a, const void *b)
+{
+	const struct line *x = a, *y = b;
+	return strcmp(x->text, y->text);
+}
+
+int cmd__mergesort(int argc, const char **argv)
+{
+	struct line *line, *p = NULL, *lines = NULL;
+	struct strbuf sb = STRBUF_INIT;
+
+	for (;;) {
+		if (strbuf_getwholeline(&sb, stdin, '\n'))
+			break;
+		line = xmalloc(sizeof(struct line));
+		line->text = strbuf_detach(&sb, NULL);
+		if (p) {
+			line->next = p->next;
+			p->next = line;
+		} else {
+			line->next = NULL;
+			lines = line;
+		}
+		p = line;
+	}
+
+	lines = llist_mergesort(lines, get_next, set_next, compare_strings);
+
+	while (lines) {
+		printf("%s", lines->text);
+		lines = lines->next;
+	}
+	return 0;
+}