Adding in support for the compare command in the API

src/main/java/org/kohsuke/github/GHCompare.java

@@ -0,0 +1,156 @@
+package org.kohsuke.github;
+
+import java.net.URL;
+import java.util.Date;
+
+/**
+ * The model user for comparing 2 commits in the GitHub API.
+ *
+ * @author Michael Clarke
+ */
+public class GHCompare {
+
+    private String url, html_url, permalink_url, diff_url, patch_url;
+    public Status status;
+    private int ahead_by, behind_by, total_commits;
+    private Commit base_commit, merge_base_commit;
+    private Commit[] commits;
+    private GHCommit.File[] files;
+
+    private GHRepository owner;
+
+    public URL getUrl() {
+        return GitHub.parseURL(url);
+    }
+
+    public URL getHtmlUrl() {
+        return GitHub.parseURL(html_url);
+    }
+
+    public URL getPermalinkUrl() {
+        return GitHub.parseURL(permalink_url);
+    }
+
+    public URL getDiffUrl() {
+        return GitHub.parseURL(diff_url);
+    }
+
+    public URL getPatchUrl() {
+        return GitHub.parseURL(patch_url);
+    }
+
+    public Status getStatus() {
+        return status;
+    }
+
+    public int getAheadBy() {
+        return ahead_by;
+    }
+
+    public int getBehindBy() {
+        return behind_by;
+    }
+
+    public int getTotalCommits() {
+        return total_commits;
+    }
+
+    public Commit getBaseCommit() {
+        return base_commit;
+    }
+
+    public Commit getMergeBaseCommit() {
+        return merge_base_commit;
+    }
+
+    public Commit[] getCommits() {
+        return commits;
+    }
+
+
+    public GHCompare wrap(GHRepository owner) {
+        this.owner = owner;
+        for (Commit commit : commits) {
+            commit.wrapUp(owner);
+        }
+        merge_base_commit.wrapUp(owner);
+        base_commit.wrapUp(owner);
+        return this;
+    }
+
+    /**
+     * Compare commits had a child commit element with additional details we want to capture.
+     * This extenstion of GHCommit provides that.
+     */
+    public static class Commit extends GHCommit {
+
+        private InnerCommit commit;
+
+        public InnerCommit getCommit() {
+            return commit;
+        }
+    }
+
+
+    public static class InnerCommit {
+        private String url, sha, message;
+        private User author, committer;
+        private Tree tree;
+
+        public String getUrl() {
+            return url;
+        }
+
+        public String getSha() {
+            return sha;
+        }
+
+        public String getMessage() {
+            return message;
+        }
+
+        public User getAuthor() {
+            return author;
+        }
+
+        public User getCommitter() {
+            return committer;
+        }
+
+        public Tree getTree() {
+            return tree;
+        }
+    }
+
+    public static class Tree {
+        private String url, sha;
+
+        public String getUrl() {
+            return url;
+        }
+
+        public String getSha() {
+            return sha;
+        }
+    }
+
+    public static class User {
+        private String name, email, date;
+
+        public String getName() {
+            return name;
+        }
+
+        public String getEmail() {
+            return email;
+        }
+
+        public Date getDate() {
+            return GitHub.parseDate(date);
+        }
+    }
+
+    public static enum Status {
+        behind, ahead, identical;
+    }
+}

src/main/java/org/kohsuke/github/GHRepository.java

@@ -393,6 +393,19 @@ public class GHRepository {
         return root.retrieve().to(String.format("/repos/%s/%s/hooks/%d", owner.login, name, id), GHHook.class).wrap(this);
     }
 
+    /**
+     * Gets a comparison between 2 points in the repository. This would be similar
+     * to calling <tt>git log id1...id2</tt> against a local repository.
+     * @param id1 an identifier for the first point to compare from, this can be a sha1 ID (for a commit, tag etc) or a direct tag name
+     * @param id2 an identifier for the second point to compare to. Can be the same as the first point.
+     * @return the comparison output
+     * @throws IOException on failure communicating with GitHub
+     */
+    public GHCompare getCompare(String id1, String id2) throws IOException {
+        GHCompare compare = root.retrieve().to(String.format("/repos/%s/%s/compare/%s...%s", owner.login, name, id1, id2), GHCompare.class);
+        return compare.wrap(this);
+    }
+
     /**
      * Gets a commit object in this repository.
      */