fix: Improve since/until when counting commits for X-Total-Count (#38243)

Follow up for https://github.com/go-gitea/gitea/pull/38204.

---------

Signed-off-by: puni9869 <80308335+puni9869@users.noreply.github.com>

tests/integration/api_repo_git_commits_test.go

@@ -241,3 +241,27 @@ func TestGetFileHistoryNotOnMaster(t *testing.T) {
 
 	assert.Equal(t, "1", resp.Header().Get("X-Total"))
 }
+
+func TestGetFileHistoryEmptyDateRange(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	// Login as User2.
+	session := loginUser(t, user.Name)
+	token := getTokenForLoggedInUser(t, session, auth_model.AccessTokenScopeReadRepository)
+
+	// readme.md exists in repo16 but no commits fall before 1970, so the date
+	// filter yields an empty range: this must return 200 with an empty list,
+	// not 404 (regression: a valid path with an empty date range was a 404).
+	req := NewRequestf(t, "GET", "/api/v1/repos/%s/repo16/commits?path=readme.md&sha=good-sign&until=1970-01-01T00:00:00Z", user.Name).
+		AddTokenAuth(token)
+	resp := MakeRequest(t, req, http.StatusOK)
+
+	apiData := DecodeJSON(t, resp, []api.Commit{})
+	assert.Empty(t, apiData)
+	assert.Equal(t, "0", resp.Header().Get("X-Total"))
+
+	// a path that does not exist must still return 404 even with a date filter
+	req = NewRequestf(t, "GET", "/api/v1/repos/%s/repo16/commits?path=does-not-exist.md&sha=good-sign&until=1970-01-01T00:00:00Z", user.Name).
+		AddTokenAuth(token)
+	MakeRequest(t, req, http.StatusNotFound)
+}