Fixed issue with dropping days (#114).

src/main/java/org/gitlab4j/api/utils/DurationUtils.java

@@ -75,6 +75,8 @@ public class DurationUtils {
                 buf.append(days).append('d').append(hours).append('h').append(minutes).append('m');
             } else if (hours > 0) {
                 buf.append(days).append('d').append(hours).append('h');
+            }  else if (days > 0) {
+                buf.append(days).append('d');
             }
 
         } else  if (days > 0) {

src/test/java/org/gitlab4j/api/TestDuration.java

@@ -3,6 +3,7 @@ package org.gitlab4j.api;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.fail;
 
+import org.gitlab4j.api.models.Duration;
 import org.gitlab4j.api.utils.DurationUtils;
 import org.junit.Test;
 
@@ -27,6 +28,29 @@ public class TestDuration {
         assertEquals(60 * 60, seconds);
     }
 
+    @Test
+    public void testRoundTrip() {
+
+        Duration duration = new Duration("2mo1d");
+        String durationString = DurationUtils.toString(duration.getSeconds(), false);
+        assertEquals("8w1d", durationString);
+        duration = new Duration(durationString);
+        assertEquals("2mo1d", duration.toString());
+
+        duration = new Duration("9w2h5m");
+        durationString = DurationUtils.toString(duration.getSeconds(), false);
+        assertEquals("9w0d2h5m", durationString);
+        duration = new Duration(durationString);
+        assertEquals("2mo1w0d2h5m", duration.toString());
+
+        duration = new Duration("2mo1w1d2h5m");
+        durationString = DurationUtils.toString(duration.getSeconds(), false);
+        assertEquals("9w1d2h5m", durationString);
+        duration = new Duration(durationString);
+        assertEquals("2mo1w1d2h5m", duration.toString());
+    }
+
+
     @Test
     public void testParseWithSpaces() {
 
@@ -108,5 +132,8 @@ public class TestDuration {
 
         duration = DurationUtils.toString(60 * 60 * 8 * 5 * 4 * 3 + 60 * 60 * 8 * 2 + 60 * 60 * 3 + 60 * 6 + 8, false);
         assertEquals("12w2d3h6m8s", duration);
+
+        duration = DurationUtils.toString(60 * 60 * 8 * 5 * 5 + 60 * 60 * 8 * 2 + 60 * 60 * 3 + 60 * 4 + 5, false);
+        assertEquals("5w2d3h4m5s", duration);
     }
 }