Add unit tests for list sorting.

Signed-off-by: Vicent Marti <tanoku@gmail.com>
Signed-off-by: Andreas Ericsson <ae@op5.se>

tests/t0403-lists.c

+#include "test_lib.h"
+#include "test_helpers.h"
+#include "commit.h"
+#include <git/odb.h>
+#include <git/commit.h>
+
+BEGIN_TEST(list_sort_test)
+
+    git_commit_list list;
+    git_commit_node *n;
+    int i, t;
+    time_t previous_time;
+
+#define TEST_SORTED() \
+    previous_time = 0;\
+    for (n = list.head; n != NULL; n = n->next)\
+    {\
+        must_be_true(n->commit->commit_time >= previous_time);\
+        previous_time = n->commit->commit_time;\
+    }
+
+    memset(&list, 0x0, sizeof(git_commit_list));
+    srand(time(NULL));
+
+    for (t = 0; t < 20; ++t)
+    {
+        const int test_size = rand() % 500 + 500;
+
+        // Purely random sorting test
+        for (i = 0; i < test_size; ++i)
+        {
+            git_commit *c = git__malloc(sizeof(git_commit));
+            c->commit_time = (time_t)rand();
+
+            git_commit_list_append(&list, c);
+        }
+
+        git_commit_list_sort(&list);
+        TEST_SORTED();
+        git_commit_list_clear(&list, 1);
+    }
+
+    // Try to sort list with all dates equal.
+    for (i = 0; i < 200; ++i)
+    {
+        git_commit *c = git__malloc(sizeof(git_commit));
+        c->commit_time = 0;
+
+        git_commit_list_append(&list, c);
+    }
+
+    git_commit_list_sort(&list);
+    TEST_SORTED();
+    git_commit_list_clear(&list, 1);
+
+    // Try to sort empty list
+    git_commit_list_sort(&list);
+    TEST_SORTED();
+
+END_TEST