• add Issue.createLabel
• add Repository.createKey
• add Repository.deleteKey
• add Repository.getBranch
• add Repository.listKeys
• add Repository.getKey
• add Repository.updatePullRequest
• deprecate Repository.updatePullRequst

• Request URL for deleting a hook (Repository.deleteHook)

• add Repository.mergePullRequest
• add Repository.updatePullRequest
• add Repository.listPullRequestFiles
• add Repository.getReadme

• add Issue.listIssueEvents

• Search returns results again

Team API

• Organization.createTeam
• Organization.getTeams
• Team.getTeam
• Team.listRepos
• Team.editTeam
• Team.listMembers
• Team.getMembership
• Team.addMembership
• Team.isManagedRepo
• Team.manageRepo
• Team.unmanageRepo
• Team.deleteTeam

• Repository#move has a new argument list User
• getRepos → listRepos
• getOrgs → listOrgs
• getGists → listGists
• getNotifications → listNotifications
• getStarredRepos → listStarredRepos

• Repository: move now works
• User: listRepos

• Repository: Replace invalid references to postTree with createTree

• Search API now returns all pages of results
• Added Repository.listReleases

Added functions for querying organization membership

• Organization.listMembers
• Organization.isMember

Added functions for issue comments

• Issue.listComments
• Issue.getComment
• Issue.editComment
• Issue.deleteComment

• all functions now return a Promise

Added methods for commenting on Gists:

• Gist.listComments
• Gist.getComment
• Gist.editComment
• Gist.deleteComment
• Gist.createComment

• Repository.deleteFile now correctly returns a promise.

Complete rewrite in ES2015.

• Promise-ified the API
• Auto-generation of documentation
• Modularized codebase
• Refactored tests to run primarily in mocha

Most of the breaking changes are just methods that got renamed. The changes to User and Organization are deeper changes that now scope a particular User or Organization to the entity they were instantiated with. You will need separate Users to query data about different user accounts.

• Github.getOrg → Github.getOrganization and requires an organization name.
• Github.getUser now requires a username.
• Issue.comment → Issue.createIssueComment
• Issue.create → Issue.createIssue
• Issue.edit → Issue.editIssue
• Issue.get → Issue.getIssue
• Issue.list → Issue.listIssues
• Repository.branch → Repository.createBranch
• Repository.collaborators → Repository.getCollaborators
• Repository.compare → Repository.compareBranches
• Repository.contents → Repository.getContents and now takes an argument for the content type
• Repository.delete has been removed.
• Repository.editHook → Repository.updateHook
• Repository.editRelease → Repository.updateRelease
• Repository.getCommit no longer takes a branch as the first argument
• Repository.getPull → Repository.getPullRequest
• Repository.getRef now returns the refspec from GitHub's API.
• Repository.getSha now returns the same data as GitHub's API. If the reqeusted object is not a directory then the response will contain a property SHA, and if the reqeusted object is a directory then the contents of the directory are stated.
• Repository.getStatuses → Repository.listStatuses
• Repository.listPulls → Repository.listPullRequests
• Repository.postBlob → Repository.createBlob
• Repository.postTree → Repository.createTree
• Repository.read remove in favor of Repository.getContents
• Repository.remove → Repository.deleteFile
• Repository.show → Repository.getDetails
• Repository.write → Repository.writeFile
• Search.code → Search.forCode
• Search.issues → Search.forIssues
• Search.repositories → Search.forRepositories
• Search.users → Search.forUsers
• The Search API no longer takes a string, it now takes an object with properties q, sort, and order to make the parts of the query easier to grok and to better match GitHub's API.
• User.gists → User.getGists
• User.notifications → User.getNotifications
• User.orgRepos → Organization.getRepos
• User.orgs → User.getOrgs
• User.repos → User.getRepos
• User.show → User.getProfile and no longer takes filtering options
• User.userStarred → User.getStarredRepos