Add api method for getting recursive tree (#78)

Coverage is ok, PR is tested

Author: dennisgranath

src/main/java/com/spotify/github/v3/clients/GitDataClient.java

@@ -249,6 +249,17 @@ public CompletableFuture<Tree> getTree(final String sha) {
     return github.request(path, Tree.class);
   }
 
+  /**
+   * Get a repository tree recursively.
+   *
+   * @param sha commit sha
+   * @return tree
+   */
+  public CompletableFuture<Tree> getRecursiveTree(final String sha) {
+    final String path = String.format(TREE_SHA_URI_TEMPLATE, owner, repo, sha);
+    return github.request(path + "?recursive=true", Tree.class);
+  }
+
   /**
    * Set a repository tree.
    *

src/test/java/com/spotify/github/v3/clients/GitDataClientTest.java

@@ -256,6 +256,22 @@ public void testGetTree() throws IOException {
     assertThat(tree.sha(), is("9c27bd92524e2b57b569d4c86695b3993d9b8f9f"));
   }
 
+  @Test
+  public void testGetRecursiveTree() throws IOException {
+    final CompletableFuture<Tree> fixture =
+            completedFuture(json.fromJson(getFixture("recursive-tree.json"), Tree.class));
+
+    when(github.request("/repos/someowner/somerepo/git/trees/thesha", Tree.class))
+            .thenReturn(fixture);
+
+    final Tree tree =
+            gitDataClient
+                    .getTree("thesha")
+                    .join();
+    assertThat(tree.sha(), is("9c27bd92524e2b57b569d4c86695b3993d9b8f9f"));
+    assertThat(tree.tree().size(), is(7));
+  }
+
   @Test
   public void testCreateTree() throws IOException {
     final TreeItem treeItem =

src/test/resources/com/spotify/github/v3/clients/recursive-tree.json

@@ -0,0 +1,61 @@
+{
+  "sha": "9c27bd92524e2b57b569d4c86695b3993d9b8f9f",
+  "url": "https://ghe.spotify.net/api/v3/repos/ugc-sharing/test-repo/git/trees/9c27bd92524e2b57b569d4c86695b3993d9b8f9f",
+  "tree": [
+    {
+      "path": "README.md",
+      "mode": "100644",
+      "type": "blob",
+      "sha": "6e091fd045dc88806e5c70357326af7fa0e1ccde",
+      "size": 12,
+      "url": "https://ghe.spotify.net/api/v3/repos/ugc-sharing/test-repo/git/blobs/6e091fd045dc88806e5c70357326af7fa0e1ccde"
+    },
+    {
+      "path": "UserGeneratedContentUtils.java",
+      "mode": "100644",
+      "type": "blob",
+      "sha": "77b3e188803e717a0a5ce53b818b0ed6fb6b8a23",
+      "size": 5340,
+      "url": "https://ghe.spotify.net/api/v3/repos/ugc-sharing/test-repo/git/blobs/77b3e188803e717a0a5ce53b818b0ed6fb6b8a23"
+    },
+    {
+      "path": "readme.md",
+      "mode": "100644",
+      "type": "blob",
+      "sha": "f09eac953086b8760f600822f057141d7b311165",
+      "size": 29,
+      "url": "https://ghe.spotify.net/api/v3/repos/ugc-sharing/test-repo/git/blobs/f09eac953086b8760f600822f057141d7b311165"
+    },
+    {
+      "path": "src",
+      "mode": "040000",
+      "type": "tree",
+      "sha": "26cd96e1394d6c4982d8cec879ad4fefa423bec8",
+      "url": "https://ghe.spotify.net/api/v3/repos/ugc-sharing/test-repo/git/trees/26cd96e1394d6c4982d8cec879ad4fefa423bec8"
+    },
+    {
+      "path": "src/public",
+      "mode": "040000",
+      "type": "tree",
+      "sha": "a296470ebb9709103115d6e21d9bc54cdfc8b120",
+      "url": "https://ghe.spotify.net/api/v3/repos/ugc-sharing/test-repo/git/trees/a296470ebb9709103115d6e21d9bc54cdfc8b120"
+    },
+    {
+      "path": "src/public/UserGeneratedContentUtils.java",
+      "mode": "100644",
+      "type": "blob",
+      "sha": "77b3e188803e717a0a5ce53b818b0ed6fb6b8a23",
+      "size": 5340,
+      "url": "https://ghe.spotify.net/api/v3/repos/ugc-sharing/test-repo/git/blobs/77b3e188803e717a0a5ce53b818b0ed6fb6b8a23"
+    },
+    {
+      "path": "src/public/test.txt",
+      "mode": "100644",
+      "type": "blob",
+      "sha": "c57eff55ebc0c54973903af5f72bac72762cf4f4",
+      "size": 12,
+      "url": "https://ghe.spotify.net/api/v3/repos/ugc-sharing/test-repo/git/blobs/c57eff55ebc0c54973903af5f72bac72762cf4f4"
+    }
+  ],
+  "truncated": false
+}