diff --git a/src/main/scala/gitbucket/core/api/AddACollaborator.scala b/src/main/scala/gitbucket/core/api/AddACollaborator.scala
new file mode 100644
index 0000000..05b1768
--- /dev/null
+++ b/src/main/scala/gitbucket/core/api/AddACollaborator.scala
@@ -0,0 +1,9 @@
+package gitbucket.core.api
+
+case class AddACollaborator(permission: String) {
+  val role: String = permission match {
+    case "admin" => "ADMIN"
+    case "push"  => "DEVELOPER"
+    case "pull"  => "GUEST"
+  }
+}
diff --git a/src/main/scala/gitbucket/core/api/ApiGroup.scala b/src/main/scala/gitbucket/core/api/ApiGroup.scala
new file mode 100644
index 0000000..5af6d4f
--- /dev/null
+++ b/src/main/scala/gitbucket/core/api/ApiGroup.scala
@@ -0,0 +1,20 @@
+package gitbucket.core.api
+
+import java.util.Date
+
+import gitbucket.core.model.Account
+
+case class ApiGroup(login: String, description: Option[String], created_at: Date) {
+  val id = 0 // dummy id
+  val url = ApiPath(s"/api/v3/orgs/${login}")
+  val html_url = ApiPath(s"/${login}")
+  val avatar_url = ApiPath(s"/${login}/_avatar")
+}
+
+object ApiGroup {
+  def apply(group: Account): ApiGroup = ApiGroup(
+    login = group.userName,
+    description = group.description,
+    created_at = group.registeredDate
+  )
+}
diff --git a/src/main/scala/gitbucket/core/api/CreateAPullRequest.scala b/src/main/scala/gitbucket/core/api/CreateAPullRequest.scala
new file mode 100644
index 0000000..aa253b8
--- /dev/null
+++ b/src/main/scala/gitbucket/core/api/CreateAPullRequest.scala
@@ -0,0 +1,16 @@
+package gitbucket.core.api
+
+case class CreateAPullRequest(
+  title: String,
+  head: String,
+  base: String,
+  body: Option[String],
+  maintainer_can_modify: Option[Boolean]
+)
+
+case class CreateAPullRequestAlt(
+  issue: Integer,
+  head: String,
+  base: String,
+  maintainer_can_modify: Option[Boolean]
+)
diff --git a/src/main/scala/gitbucket/core/api/CreateAUser.scala b/src/main/scala/gitbucket/core/api/CreateAUser.scala
new file mode 100644
index 0000000..f2cd9f0
--- /dev/null
+++ b/src/main/scala/gitbucket/core/api/CreateAUser.scala
@@ -0,0 +1,11 @@
+package gitbucket.core.api
+
+case class CreateAUser(
+  login: String,
+  password: String,
+  email: String,
+  fullName: Option[String],
+  isAdmin: Option[Boolean],
+  description: Option[String],
+  url: Option[String]
+)
diff --git a/src/main/scala/gitbucket/core/api/JsonFormat.scala b/src/main/scala/gitbucket/core/api/JsonFormat.scala
index 8579926..96fbd69 100644
--- a/src/main/scala/gitbucket/core/api/JsonFormat.scala
+++ b/src/main/scala/gitbucket/core/api/JsonFormat.scala
@@ -24,6 +24,7 @@
         }, { case x: Date => JString(OffsetDateTime.ofInstant(x.toInstant, ZoneId.of("UTC")).format(parserISO)) }
     )
   ) + FieldSerializer[ApiUser]() +
+    FieldSerializer[ApiGroup]() +
     FieldSerializer[ApiPullRequest]() +
     FieldSerializer[ApiRepository]() +
     FieldSerializer[ApiCommitListItem.Parent]() +
diff --git a/src/main/scala/gitbucket/core/api/UpdateAUser.scala b/src/main/scala/gitbucket/core/api/UpdateAUser.scala
new file mode 100644
index 0000000..1981c78
--- /dev/null
+++ b/src/main/scala/gitbucket/core/api/UpdateAUser.scala
@@ -0,0 +1,11 @@
+package gitbucket.core.api
+
+case class UpdateAUser(
+  name: Option[String],
+  email: Option[String],
+  blog: Option[String],
+  company: Option[String],
+  location: Option[String],
+  hireable: Option[Boolean],
+  bio: Option[String]
+)
diff --git a/src/main/scala/gitbucket/core/controller/ApiController.scala b/src/main/scala/gitbucket/core/controller/ApiController.scala
index 5e78b20..1cf08af 100644
--- a/src/main/scala/gitbucket/core/controller/ApiController.scala
+++ b/src/main/scala/gitbucket/core/controller/ApiController.scala
@@ -33,6 +33,7 @@
     with RepositoryCreationService
     with IssueCreationService
     with HandleCommentService
+    with MergeService
     with WebHookService
     with WebHookPullRequestService
     with WebHookIssueCommentService
@@ -40,6 +41,7 @@
     with WikiService
     with ActivityService
     with PrioritiesService
+    with AdminAuthenticator
     with OwnerAuthenticator
     with UsersAuthenticator
     with GroupManagerAuthenticator
diff --git a/src/main/scala/gitbucket/core/controller/PullRequestsController.scala b/src/main/scala/gitbucket/core/controller/PullRequestsController.scala
index 3b5ab5c..18fd38d 100644
--- a/src/main/scala/gitbucket/core/controller/PullRequestsController.scala
+++ b/src/main/scala/gitbucket/core/controller/PullRequestsController.scala
@@ -15,7 +15,7 @@
 import gitbucket.core.util._
 import org.scalatra.forms._
 import org.eclipse.jgit.api.Git
-import org.eclipse.jgit.lib.PersonIdent
+import org.eclipse.jgit.lib.{ObjectId, PersonIdent}
 import org.eclipse.jgit.revwalk.RevWalk
 import org.scalatra.BadRequest
 
@@ -412,97 +412,68 @@
               .map(_.repository.repositoryName)
           };
           originRepository <- getRepository(originOwner, originRepositoryName)) yield {
-      using(
-        Git.open(getRepositoryDir(originRepository.owner, originRepository.name)),
-        Git.open(getRepositoryDir(forkedRepository.owner, forkedRepository.name))
-      ) {
-        case (oldGit, newGit) =>
-          val (oldId, newId) =
-            if (originRepository.branchList.contains(originId)) {
-              val forkedId2 =
-                forkedRepository.tags.collectFirst { case x if x.name == forkedId => x.id }.getOrElse(forkedId)
+      val (oldId, newId) =
+        getPullRequestCommitFromTo(originRepository, forkedRepository, originId, forkedId)
 
-              val originId2 = JGitUtil.getForkedCommitId(
-                oldGit,
-                newGit,
-                originRepository.owner,
-                originRepository.name,
-                originId,
-                forkedRepository.owner,
-                forkedRepository.name,
-                forkedId2
-              )
+      (oldId, newId) match {
+        case (Some(oldId), Some(newId)) => {
+          val (commits, diffs) = getRequestCompareInfo(
+            originRepository.owner,
+            originRepository.name,
+            oldId.getName,
+            forkedRepository.owner,
+            forkedRepository.name,
+            newId.getName
+          )
 
-              (Option(oldGit.getRepository.resolve(originId2)), Option(newGit.getRepository.resolve(forkedId2)))
-
-            } else {
-              val originId2 =
-                originRepository.tags.collectFirst { case x if x.name == originId => x.id }.getOrElse(originId)
-              val forkedId2 =
-                forkedRepository.tags.collectFirst { case x if x.name == forkedId => x.id }.getOrElse(forkedId)
-
-              (Option(oldGit.getRepository.resolve(originId2)), Option(newGit.getRepository.resolve(forkedId2)))
-            }
-
-          (oldId, newId) match {
-            case (Some(oldId), Some(newId)) => {
-              val (commits, diffs) = getRequestCompareInfo(
-                originRepository.owner,
-                originRepository.name,
-                oldId.getName,
-                forkedRepository.owner,
-                forkedRepository.name,
-                newId.getName
-              )
-
-              val title = if (commits.flatten.length == 1) {
-                commits.flatten.head.shortMessage
-              } else {
-                val text = forkedId.replaceAll("[\\-_]", " ")
-                text.substring(0, 1).toUpperCase + text.substring(1)
-              }
-
-              html.compare(
-                title,
-                commits,
-                diffs,
-                ((forkedRepository.repository.originUserName, forkedRepository.repository.originRepositoryName) match {
-                  case (Some(userName), Some(repositoryName)) =>
-                    getRepository(userName, repositoryName) match {
-                      case Some(x) => x.repository :: getForkedRepositories(userName, repositoryName)
-                      case None    => getForkedRepositories(userName, repositoryName)
-                    }
-                  case _ =>
-                    forkedRepository.repository :: getForkedRepositories(forkedRepository.owner, forkedRepository.name)
-                }).map { repository =>
-                  (repository.userName, repository.repositoryName, repository.defaultBranch)
-                },
-                commits.flatten
-                  .map(commit => getCommitComments(forkedRepository.owner, forkedRepository.name, commit.id, false))
-                  .flatten
-                  .toList,
-                originId,
-                forkedId,
-                oldId.getName,
-                newId.getName,
-                getContentTemplate(originRepository, "PULL_REQUEST_TEMPLATE"),
-                forkedRepository,
-                originRepository,
-                forkedRepository,
-                hasDeveloperRole(originRepository.owner, originRepository.name, context.loginAccount),
-                getAssignableUserNames(originRepository.owner, originRepository.name),
-                getMilestones(originRepository.owner, originRepository.name),
-                getPriorities(originRepository.owner, originRepository.name),
-                getLabels(originRepository.owner, originRepository.name)
-              )
-            }
-            case (oldId, newId) =>
-              redirect(
-                s"/${forkedRepository.owner}/${forkedRepository.name}/compare/" +
-                  s"${originOwner}:${oldId.map(_ => originId).getOrElse(originRepository.repository.defaultBranch)}..." +
-                  s"${forkedOwner}:${newId.map(_ => forkedId).getOrElse(forkedRepository.repository.defaultBranch)}"
-              )
+          val title = if (commits.flatten.length == 1) {
+            commits.flatten.head.shortMessage
+          } else {
+            val text = forkedId.replaceAll("[\\-_]", " ")
+            text.substring(0, 1).toUpperCase + text.substring(1)
           }
+
+          html.compare(
+            title,
+            commits,
+            diffs,
+            ((forkedRepository.repository.originUserName, forkedRepository.repository.originRepositoryName) match {
+              case (Some(userName), Some(repositoryName)) =>
+                getRepository(userName, repositoryName) match {
+                  case Some(x) => x.repository :: getForkedRepositories(userName, repositoryName)
+                  case None    => getForkedRepositories(userName, repositoryName)
+                }
+              case _ =>
+                forkedRepository.repository :: getForkedRepositories(forkedRepository.owner, forkedRepository.name)
+            }).map { repository =>
+              (repository.userName, repository.repositoryName, repository.defaultBranch)
+            },
+            commits.flatten
+              .map(commit => getCommitComments(forkedRepository.owner, forkedRepository.name, commit.id, false))
+              .flatten
+              .toList,
+            originId,
+            forkedId,
+            oldId.getName,
+            newId.getName,
+            getContentTemplate(originRepository, "PULL_REQUEST_TEMPLATE"),
+            forkedRepository,
+            originRepository,
+            forkedRepository,
+            hasDeveloperRole(originRepository.owner, originRepository.name, context.loginAccount),
+            getAssignableUserNames(originRepository.owner, originRepository.name),
+            getMilestones(originRepository.owner, originRepository.name),
+            getPriorities(originRepository.owner, originRepository.name),
+            getLabels(originRepository.owner, originRepository.name)
+          )
+        }
+        case (oldId, newId) =>
+          redirect(
+            s"/${forkedRepository.owner}/${forkedRepository.name}/compare/" +
+              s"${originOwner}:${oldId.map(_ => originId).getOrElse(originRepository.repository.defaultBranch)}..." +
+              s"${forkedOwner}:${newId.map(_ => forkedId).getOrElse(forkedRepository.repository.defaultBranch)}"
+          )
+
       }
     }) getOrElse NotFound()
   })
@@ -653,20 +624,6 @@
     html.proposals(proposedBranches, targetRepository, repository)
   })
 
-  /**
-   * Parses branch identifier and extracts owner and branch name as tuple.
-   *
-   * - "owner:branch" to ("owner", "branch")
-   * - "branch" to ("defaultOwner", "branch")
-   */
-  private def parseCompareIdentifier(value: String, defaultOwner: String): (String, String) =
-    if (value.contains(':')) {
-      val array = value.split(":")
-      (array(0), array(1))
-    } else {
-      (defaultOwner, value)
-    }
-
   private def searchPullRequests(userName: Option[String], repository: RepositoryService.RepositoryInfo) =
     defining(repository.owner, repository.name) {
       case (owner, repoName) =>
diff --git a/src/main/scala/gitbucket/core/controller/api/ApiIssueControllerBase.scala b/src/main/scala/gitbucket/core/controller/api/ApiIssueControllerBase.scala
index 6fe0632..12f44be 100644
--- a/src/main/scala/gitbucket/core/controller/api/ApiIssueControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/api/ApiIssueControllerBase.scala
@@ -5,7 +5,7 @@
 import gitbucket.core.service.{AccountService, IssueCreationService, IssuesService, MilestonesService}
 import gitbucket.core.service.IssuesService.IssueSearchCondition
 import gitbucket.core.service.PullRequestService.PullRequestLimit
-import gitbucket.core.util.{ReadableUsersAuthenticator, ReferrerAuthenticator, RepositoryName}
+import gitbucket.core.util.{ReadableUsersAuthenticator, ReferrerAuthenticator, RepositoryName, UsersAuthenticator}
 import gitbucket.core.util.Implicits._
 
 trait ApiIssueControllerBase extends ControllerBase {
@@ -18,6 +18,7 @@
   /*
    * i. List issues
    * https://developer.github.com/v3/issues/#list-issues
+   * requested: 1743
    */
 
   /*
diff --git a/src/main/scala/gitbucket/core/controller/api/ApiIssueLabelControllerBase.scala b/src/main/scala/gitbucket/core/controller/api/ApiIssueLabelControllerBase.scala
index 0f9e4cc..307a4db 100644
--- a/src/main/scala/gitbucket/core/controller/api/ApiIssueLabelControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/api/ApiIssueLabelControllerBase.scala
@@ -109,26 +109,84 @@
    * vi. List labels on an issue
    * https://developer.github.com/v3/issues/labels/#list-labels-on-an-issue
    */
+  get("/api/v3/repos/:owner/:repository/issues/:id/labels")(referrersOnly { repository =>
+    JsonFormat(getIssueLabels(repository.owner, repository.name, params("id").toInt).map { l =>
+      ApiLabel(l, RepositoryName(repository.owner, repository.name))
+    })
+  })
 
   /*
    * vii. Add labels to an issue
    * https://developer.github.com/v3/issues/labels/#add-labels-to-an-issue
    */
+  post("/api/v3/repos/:owner/:repository/issues/:id/labels")(writableUsersOnly { repository =>
+    JsonFormat(for {
+      data <- extractFromJsonBody[Seq[String]];
+      issueId <- params("id").toIntOpt
+    } yield {
+      data.map { labelName =>
+        val label = getLabel(repository.owner, repository.name, labelName).getOrElse(
+          getLabel(
+            repository.owner,
+            repository.name,
+            createLabel(repository.owner, repository.name, labelName)
+          ).get
+        )
+        registerIssueLabel(repository.owner, repository.name, issueId, label.labelId, true)
+        ApiLabel(label, RepositoryName(repository.owner, repository.name))
+      }
+    })
+  })
 
   /*
    * viii. Remove a label from an issue
    * https://developer.github.com/v3/issues/labels/#remove-a-label-from-an-issue
    */
+  delete("/api/v3/repos/:owner/:repository/issues/:id/labels/:name")(writableUsersOnly { repository =>
+    val issueId = params("id").toInt
+    val labelName = params("name")
+    getLabel(repository.owner, repository.name, labelName) match {
+      case Some(label) =>
+        deleteIssueLabel(repository.owner, repository.name, issueId, label.labelId, true)
+        JsonFormat(Seq(label))
+      case None =>
+        NotFound()
+    }
+  })
 
   /*
    * ix. Replace all labels for an issue
    * https://developer.github.com/v3/issues/labels/#replace-all-labels-for-an-issue
    */
+  put("/api/v3/repos/:owner/:repository/issues/:id/labels")(writableUsersOnly { repository =>
+    JsonFormat(for {
+      data <- extractFromJsonBody[Seq[String]];
+      issueId <- params("id").toIntOpt
+    } yield {
+      deleteAllIssueLabels(repository.owner, repository.name, issueId, true)
+      data.map { labelName =>
+        val label = getLabel(repository.owner, repository.name, labelName).getOrElse(
+          getLabel(
+            repository.owner,
+            repository.name,
+            createLabel(repository.owner, repository.name, labelName)
+          ).get
+        )
+        registerIssueLabel(repository.owner, repository.name, issueId, label.labelId, true)
+        ApiLabel(label, RepositoryName(repository.owner, repository.name))
+      }
+    })
+  })
 
   /*
    * x. Remove all labels from an issue
    * https://developer.github.com/v3/issues/labels/#remove-all-labels-from-an-issue
    */
+  delete("/api/v3/repos/:owner/:repository/issues/:id/labels")(writableUsersOnly { repository =>
+    val issueId = params("id").toInt
+    deleteAllIssueLabels(repository.owner, repository.name, issueId, true)
+    NoContent()
+  })
 
   /*
  * xi Get labels for every issue in a milestone
diff --git a/src/main/scala/gitbucket/core/controller/api/ApiOrganizationControllerBase.scala b/src/main/scala/gitbucket/core/controller/api/ApiOrganizationControllerBase.scala
index 0b64c9f..85ca93c 100644
--- a/src/main/scala/gitbucket/core/controller/api/ApiOrganizationControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/api/ApiOrganizationControllerBase.scala
@@ -1,26 +1,36 @@
 package gitbucket.core.controller.api
-import gitbucket.core.api.{ApiRepository, ApiUser, JsonFormat}
+import gitbucket.core.api.{ApiGroup, ApiRepository, ApiUser, JsonFormat}
 import gitbucket.core.controller.ControllerBase
 import gitbucket.core.service.{AccountService, RepositoryService}
 import gitbucket.core.util.Implicits._
+import gitbucket.core.util.UsersAuthenticator
 
 trait ApiOrganizationControllerBase extends ControllerBase {
-  self: RepositoryService with AccountService =>
+  self: RepositoryService with AccountService with UsersAuthenticator =>
 
   /*
    * i. List your organizations
    * https://developer.github.com/v3/orgs/#list-your-organizations
    */
+  get("/api/v3/user/orgs")(usersOnly {
+    JsonFormat(getGroupsByUserName(context.loginAccount.get.userName).flatMap(getAccountByUserName(_)).map(ApiGroup(_)))
+  })
 
   /*
    * ii. List all organizations
    * https://developer.github.com/v3/orgs/#list-all-organizations
    */
+  get("/api/v3/organizations") {
+    JsonFormat(getAllUsers(false, true).filter(a => a.isGroupAccount).map(ApiGroup(_)))
+  }
 
   /*
    * iii. List user organizations
    * https://developer.github.com/v3/orgs/#list-user-organizations
    */
+  get("/api/v3/users/:userName/orgs") {
+    JsonFormat(getGroupsByUserName(params("userName")).flatMap(getAccountByUserName(_)).map(ApiGroup(_)))
+  }
 
   /**
    * iv. Get an organization
@@ -28,7 +38,26 @@
    */
   get("/api/v3/orgs/:groupName") {
     getAccountByUserName(params("groupName")).filter(account => account.isGroupAccount).map { account =>
-      JsonFormat(ApiUser(account))
+      JsonFormat(ApiGroup(account))
     } getOrElse NotFound()
   }
+
+  /*
+   * v. Edit an organization
+   * https://developer.github.com/v3/orgs/#edit-an-organization
+   */
+
+  /*
+   * ghe: i. Create an organization
+   * https://developer.github.com/enterprise/2.14/v3/enterprise-admin/orgs/#create-an-organization
+   */
+
+  /*
+   * ghe: ii. Rename an organization
+   * https://developer.github.com/enterprise/2.14/v3/enterprise-admin/orgs/#rename-an-organization
+   */
+
+  /*
+ * should implement delete an organization API?
+ */
 }
diff --git a/src/main/scala/gitbucket/core/controller/api/ApiPullRequestControllerBase.scala b/src/main/scala/gitbucket/core/controller/api/ApiPullRequestControllerBase.scala
index fe66183..13cc75d 100644
--- a/src/main/scala/gitbucket/core/controller/api/ApiPullRequestControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/api/ApiPullRequestControllerBase.scala
@@ -2,19 +2,28 @@
 import gitbucket.core.api._
 import gitbucket.core.controller.ControllerBase
 import gitbucket.core.model.{Account, Issue, PullRequest, Repository}
-import gitbucket.core.service.{AccountService, IssuesService, PullRequestService, RepositoryService}
+import gitbucket.core.service._
 import gitbucket.core.service.IssuesService.IssueSearchCondition
 import gitbucket.core.service.PullRequestService.PullRequestLimit
 import gitbucket.core.util.Directory.getRepositoryDir
 import gitbucket.core.util.Implicits._
 import gitbucket.core.util.JGitUtil.CommitInfo
 import gitbucket.core.util.SyntaxSugars.using
-import gitbucket.core.util.{ReferrerAuthenticator, RepositoryName}
+import gitbucket.core.util._
 import org.eclipse.jgit.api.Git
+import org.scalatra.NoContent
+
 import scala.collection.JavaConverters._
 
 trait ApiPullRequestControllerBase extends ControllerBase {
-  self: AccountService with IssuesService with PullRequestService with RepositoryService with ReferrerAuthenticator =>
+  self: AccountService
+    with IssuesService
+    with PullRequestService
+    with RepositoryService
+    with MergeService
+    with ReferrerAuthenticator
+    with ReadableUsersAuthenticator
+    with WritableUsersAuthenticator =>
 
   /*
    * i. Link Relations
@@ -25,9 +34,6 @@
    * ii. List pull requests
    * https://developer.github.com/v3/pulls/#list-pull-requests
    */
-  /**
-   * https://developer.github.com/v3/pulls/#list-pull-requests
-   */
   get("/api/v3/repos/:owner/:repository/pulls")(referrersOnly { repository =>
     val page = IssueSearchCondition.page(request)
     // TODO: more api spec condition
@@ -62,45 +68,92 @@
    * iii. Get a single pull request
    * https://developer.github.com/v3/pulls/#get-a-single-pull-request
    */
-  /**
-   * https://developer.github.com/v3/pulls/#get-a-single-pull-request
-   */
   get("/api/v3/repos/:owner/:repository/pulls/:id")(referrersOnly { repository =>
     (for {
       issueId <- params("id").toIntOpt
-      (issue, pullRequest) <- getPullRequest(repository.owner, repository.name, issueId)
-      users = getAccountsByUserNames(
-        Set(repository.owner, pullRequest.requestUserName, issue.openedUserName),
-        Set.empty
-      )
-      baseOwner <- users.get(repository.owner)
-      headOwner <- users.get(pullRequest.requestUserName)
-      issueUser <- users.get(issue.openedUserName)
-      assignee = issue.assignedUserName.flatMap { userName =>
-        getAccountByUserName(userName, false)
-      }
-      headRepo <- getRepository(pullRequest.requestUserName, pullRequest.requestRepositoryName)
     } yield {
-      JsonFormat(
-        ApiPullRequest(
-          issue = issue,
-          pullRequest = pullRequest,
-          headRepo = ApiRepository(headRepo, ApiUser(headOwner)),
-          baseRepo = ApiRepository(repository, ApiUser(baseOwner)),
-          user = ApiUser(issueUser),
-          labels = getIssueLabels(repository.owner, repository.name, issue.issueId)
-            .map(ApiLabel(_, RepositoryName(repository))),
-          assignee = assignee.map(ApiUser.apply),
-          mergedComment = getMergedComment(repository.owner, repository.name, issue.issueId)
-        )
-      )
+      JsonFormat(getApiPullRequest(repository, issueId))
     }) getOrElse NotFound()
   })
 
   /*
    * iv. Create a pull request
    * https://developer.github.com/v3/pulls/#create-a-pull-request
+   * requested #1843
    */
+  post("/api/v3/repos/:owner/:repository/pulls")(readableUsersOnly { repository =>
+    (for {
+      data <- extractFromJsonBody[Either[CreateAPullRequest, CreateAPullRequestAlt]]
+    } yield {
+      data match {
+        case Left(createPullReq) =>
+          val (reqOwner, reqBranch) = parseCompareIdentifier(createPullReq.head, repository.owner)
+          getRepository(reqOwner, repository.name)
+            .flatMap {
+              forkedRepository =>
+                getPullRequestCommitFromTo(repository, forkedRepository, createPullReq.base, reqBranch) match {
+                  case (Some(commitIdFrom), Some(commitIdTo)) =>
+                    val issueId = insertIssue(
+                      owner = repository.owner,
+                      repository = repository.name,
+                      loginUser = context.loginAccount.get.userName,
+                      title = createPullReq.title,
+                      content = createPullReq.body,
+                      assignedUserName = None,
+                      milestoneId = None,
+                      priorityId = None,
+                      isPullRequest = true
+                    )
+
+                    createPullRequest(
+                      originUserName = repository.owner,
+                      originRepositoryName = repository.name,
+                      issueId = issueId,
+                      originBranch = createPullReq.base,
+                      requestUserName = reqOwner,
+                      requestRepositoryName = repository.name,
+                      requestBranch = reqBranch,
+                      commitIdFrom = commitIdFrom.getName,
+                      commitIdTo = commitIdTo.getName
+                    )
+                    getApiPullRequest(repository, issueId).map(JsonFormat(_))
+                  case _ =>
+                    None
+                }
+            }
+            .getOrElse {
+              NotFound()
+            }
+        case Right(createPullReqAlt) =>
+          val (reqOwner, reqBranch) = parseCompareIdentifier(createPullReqAlt.head, repository.owner)
+          getRepository(reqOwner, repository.name)
+            .flatMap {
+              forkedRepository =>
+                getPullRequestCommitFromTo(repository, forkedRepository, createPullReqAlt.base, reqBranch) match {
+                  case (Some(commitIdFrom), Some(commitIdTo)) =>
+                    changeIssueToPullRequest(repository.owner, repository.name, createPullReqAlt.issue)
+                    createPullRequest(
+                      originUserName = repository.owner,
+                      originRepositoryName = repository.name,
+                      issueId = createPullReqAlt.issue,
+                      originBranch = createPullReqAlt.base,
+                      requestUserName = reqOwner,
+                      requestRepositoryName = repository.name,
+                      requestBranch = reqBranch,
+                      commitIdFrom = commitIdFrom.getName,
+                      commitIdTo = commitIdTo.getName
+                    )
+                    getApiPullRequest(repository, createPullReqAlt.issue).map(JsonFormat(_))
+                  case _ =>
+                    None
+                }
+            }
+            .getOrElse {
+              NotFound()
+            }
+      }
+    })
+  })
 
   /*
    * v. Update a pull request
@@ -111,9 +164,6 @@
    * vi. List commits on a pull request
    * https://developer.github.com/v3/pulls/#list-commits-on-a-pull-request
    */
-  /**
-   * https://developer.github.com/v3/pulls/#list-commits-on-a-pull-request
-   */
   get("/api/v3/repos/:owner/:repository/pulls/:id/commits")(referrersOnly { repository =>
     val owner = repository.owner
     val name = repository.name
@@ -148,6 +198,18 @@
    * viii. Get if a pull request has been merged
    * https://developer.github.com/v3/pulls/#get-if-a-pull-request-has-been-merged
    */
+  get("/api/v3/repos/:owner/:repository/pulls/:id/merge")(referrersOnly { repository =>
+    (for {
+      issueId <- params("id").toIntOpt
+      (issue, pullReq) <- getPullRequest(repository.owner, repository.name, issueId)
+    } yield {
+      if (checkConflict(repository.owner, repository.name, pullReq.branch, issueId).isDefined) {
+        NoContent
+      } else {
+        NotFound
+      }
+    }).getOrElse(NotFound)
+  })
 
   /*
    * ix. Merge a pull request (Merge Button)
@@ -155,7 +217,36 @@
    */
 
   /*
- * x. Labels, assignees, and milestones
- * https://developer.github.com/v3/pulls/#labels-assignees-and-milestones
- */
+   * x. Labels, assignees, and milestones
+   * https://developer.github.com/v3/pulls/#labels-assignees-and-milestones
+   */
+
+  private def getApiPullRequest(repository: RepositoryService.RepositoryInfo, issueId: Int): Option[ApiPullRequest] = {
+    for {
+      (issue, pullRequest) <- getPullRequest(repository.owner, repository.name, issueId)
+      users = getAccountsByUserNames(
+        Set(repository.owner, pullRequest.requestUserName, issue.openedUserName),
+        Set.empty
+      )
+      baseOwner <- users.get(repository.owner)
+      headOwner <- users.get(pullRequest.requestUserName)
+      issueUser <- users.get(issue.openedUserName)
+      assignee = issue.assignedUserName.flatMap { userName =>
+        getAccountByUserName(userName, false)
+      }
+      headRepo <- getRepository(pullRequest.requestUserName, pullRequest.requestRepositoryName)
+    } yield {
+      ApiPullRequest(
+        issue = issue,
+        pullRequest = pullRequest,
+        headRepo = ApiRepository(headRepo, ApiUser(headOwner)),
+        baseRepo = ApiRepository(repository, ApiUser(baseOwner)),
+        user = ApiUser(issueUser),
+        labels = getIssueLabels(repository.owner, repository.name, issue.issueId)
+          .map(ApiLabel(_, RepositoryName(repository))),
+        assignee = assignee.map(ApiUser.apply),
+        mergedComment = getMergedComment(repository.owner, repository.name, issue.issueId)
+      )
+    }
+  }
 }
diff --git a/src/main/scala/gitbucket/core/controller/api/ApiRepositoryCollaboratorControllerBase.scala b/src/main/scala/gitbucket/core/controller/api/ApiRepositoryCollaboratorControllerBase.scala
index 402b7a3..f8fe1e5 100644
--- a/src/main/scala/gitbucket/core/controller/api/ApiRepositoryCollaboratorControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/api/ApiRepositoryCollaboratorControllerBase.scala
@@ -1,12 +1,13 @@
 package gitbucket.core.controller.api
-import gitbucket.core.api.{ApiUser, JsonFormat}
+import gitbucket.core.api.{AddACollaborator, ApiUser, JsonFormat}
 import gitbucket.core.controller.ControllerBase
 import gitbucket.core.service.{AccountService, RepositoryService}
 import gitbucket.core.util.Implicits._
-import gitbucket.core.util.ReferrerAuthenticator
+import gitbucket.core.util.{OwnerAuthenticator, ReferrerAuthenticator}
+import org.scalatra.NoContent
 
 trait ApiRepositoryCollaboratorControllerBase extends ControllerBase {
-  self: RepositoryService with AccountService with ReferrerAuthenticator =>
+  self: RepositoryService with AccountService with ReferrerAuthenticator with OwnerAuthenticator =>
 
   /*
    * i. List collaborators
@@ -31,10 +32,24 @@
   /*
    * iv. Add user as a collaborator
    * https://developer.github.com/v3/repos/collaborators/#add-user-as-a-collaborator
+   * requested #1586
    */
+  put("/api/v3/repos/:owner/:repository/collaborators/:userName")(ownerOnly { repository =>
+    for {
+      data <- extractFromJsonBody[AddACollaborator]
+    } yield {
+      addCollaborator(repository.owner, repository.name, params("userName"), data.role)
+      NoContent()
+    }
+  })
 
   /*
- * v. Remove user as a collaborator
- * https://developer.github.com/v3/repos/collaborators/#remove-user-as-a-collaborator
- */
+   * v. Remove user as a collaborator
+   * https://developer.github.com/v3/repos/collaborators/#remove-user-as-a-collaborator
+   * requested #1586
+   */
+  delete("/api/v3/repos/:owner/:repository/collaborators/:userName")(ownerOnly { repository =>
+    removeCollaborator(repository.owner, repository.name, params("userName"))
+    NoContent()
+  })
 }
diff --git a/src/main/scala/gitbucket/core/controller/api/ApiRepositoryContentsControllerBase.scala b/src/main/scala/gitbucket/core/controller/api/ApiRepositoryContentsControllerBase.scala
index c1d128b..d0dae95 100644
--- a/src/main/scala/gitbucket/core/controller/api/ApiRepositoryContentsControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/api/ApiRepositoryContentsControllerBase.scala
@@ -103,16 +103,19 @@
   /*
    * iii. Create a file
    * https://developer.github.com/v3/repos/contents/#create-a-file
+   * requested #2112
    */
 
   /*
    * iv. Update a file
    * https://developer.github.com/v3/repos/contents/#update-a-file
+   * requested #2112
    */
 
   /*
    * v. Delete a file
    * https://developer.github.com/v3/repos/contents/#delete-a-file
+   * should be implemented
    */
 
   /*
diff --git a/src/main/scala/gitbucket/core/controller/api/ApiUserControllerBase.scala b/src/main/scala/gitbucket/core/controller/api/ApiUserControllerBase.scala
index 7c596fd..4b69621 100644
--- a/src/main/scala/gitbucket/core/controller/api/ApiUserControllerBase.scala
+++ b/src/main/scala/gitbucket/core/controller/api/ApiUserControllerBase.scala
@@ -1,11 +1,13 @@
 package gitbucket.core.controller.api
-import gitbucket.core.api.{ApiUser, JsonFormat}
+import gitbucket.core.api.{ApiUser, CreateAUser, JsonFormat, UpdateAUser}
 import gitbucket.core.controller.ControllerBase
 import gitbucket.core.service.{AccountService, RepositoryService}
+import gitbucket.core.util.{AdminAuthenticator, UsersAuthenticator}
 import gitbucket.core.util.Implicits._
+import org.scalatra.NoContent
 
 trait ApiUserControllerBase extends ControllerBase {
-  self: RepositoryService with AccountService =>
+  self: RepositoryService with AccountService with AdminAuthenticator with UsersAuthenticator =>
 
   /**
    * i. Get a single user
@@ -32,6 +34,18 @@
    * iii. Update the authenticated user
    * https://developer.github.com/v3/users/#update-the-authenticated-user
    */
+  patch("/api/v3/user")(usersOnly {
+    (for {
+      data <- extractFromJsonBody[UpdateAUser]
+    } yield {
+      val loginAccount = context.loginAccount.get
+      val updatedAccount = loginAccount.copy(
+        mailAddress = data.email.getOrElse(loginAccount.mailAddress)
+      )
+      updateAccount(updatedAccount)
+      JsonFormat(ApiUser(updatedAccount))
+    })
+  })
 
   /*
    * iv. Get contextual information about a user
@@ -39,8 +53,62 @@
    */
 
   /*
- * v. Get all users
- * https://developer.github.com/v3/users/#get-all-users
- */
+   * v. Get all users
+   * https://developer.github.com/v3/users/#get-all-users
+   */
+  get("/api/v3/users") {
+    JsonFormat(getAllUsers(false, false).map(a => ApiUser(a)))
+  }
 
+  /*
+   * ghe: i. Create a new user
+   * https://developer.github.com/enterprise/2.14/v3/enterprise-admin/users/#create-a-new-user
+   */
+  post("/api/v3/admin/users")(adminOnly {
+    for {
+      data <- extractFromJsonBody[CreateAUser]
+    } yield {
+      val user = createAccount(
+        data.login,
+        data.password,
+        data.fullName.getOrElse(data.login),
+        data.email,
+        data.isAdmin.getOrElse(false),
+        data.description,
+        data.url
+      )
+      JsonFormat(ApiUser(user))
+    }
+  })
+
+  /*
+   * ghe: vii. Suspend a user
+   * https://developer.github.com/enterprise/2.14/v3/enterprise-admin/users/#suspend-a-user
+   */
+  put("/api/v3/users/:userName/suspended")(adminOnly {
+    val userName = params("userName")
+    getAccountByUserName(userName) match {
+      case Some(targetAccount) =>
+        removeUserRelatedData(userName)
+        updateAccount(targetAccount.copy(isRemoved = true))
+        NoContent()
+      case None =>
+        NotFound()
+    }
+  })
+
+  /*
+   * ghe: vii. Unsuspend a user
+   * https://developer.github.com/enterprise/2.14/v3/enterprise-admin/users/#unsuspend-a-user
+   */
+  delete("/api/v3/users/:userName/suspended")(adminOnly {
+    val userName = params("userName")
+    getAccountByUserName(userName) match {
+      case Some(targetAccount) =>
+        updateAccount(targetAccount.copy(isRemoved = false))
+        NoContent()
+      case None =>
+        NotFound()
+    }
+  })
 }
diff --git a/src/main/scala/gitbucket/core/service/AccountService.scala b/src/main/scala/gitbucket/core/service/AccountService.scala
index b8bcba4..151edb0 100644
--- a/src/main/scala/gitbucket/core/service/AccountService.scala
+++ b/src/main/scala/gitbucket/core/service/AccountService.scala
@@ -164,8 +164,8 @@
     isAdmin: Boolean,
     description: Option[String],
     url: Option[String]
-  )(implicit s: Session): Unit =
-    Accounts insert Account(
+  )(implicit s: Session): Account = {
+    val account = Account(
       userName = userName,
       password = password,
       fullName = fullName,
@@ -180,6 +180,9 @@
       isRemoved = false,
       description = description
     )
+    Accounts insert account
+    account
+  }
 
   def suspendAccount(account: Account)(implicit s: Session): Unit = {
     // Remove from GROUP_MEMBER and COLLABORATOR
diff --git a/src/main/scala/gitbucket/core/service/IssuesService.scala b/src/main/scala/gitbucket/core/service/IssuesService.scala
index 86103d2..29665bd 100644
--- a/src/main/scala/gitbucket/core/service/IssuesService.scala
+++ b/src/main/scala/gitbucket/core/service/IssuesService.scala
@@ -475,6 +475,25 @@
     IssueLabels filter (_.byPrimaryKey(owner, repository, issueId, labelId)) delete
   }
 
+  def deleteAllIssueLabels(owner: String, repository: String, issueId: Int, insertComment: Boolean = false)(
+    implicit context: Context,
+    s: Session
+  ): Int = {
+    if (insertComment) {
+      IssueComments insert IssueComment(
+        userName = owner,
+        repositoryName = repository,
+        issueId = issueId,
+        action = "delete_label",
+        commentedUserName = context.loginAccount.map(_.userName).getOrElse("Unknown user"),
+        content = "All labels",
+        registeredDate = currentDate,
+        updatedDate = currentDate
+      )
+    }
+    IssueLabels filter (_.byIssue(owner, repository, issueId)) delete
+  }
+
   def createComment(
     owner: String,
     repository: String,
@@ -507,6 +526,15 @@
       .update(title, content, currentDate)
   }
 
+  def changeIssueToPullRequest(owner: String, repository: String, issueId: Int)(implicit s: Session) = {
+    Issues
+      .filter(_.byPrimaryKey(owner, repository, issueId))
+      .map { t =>
+        t.pullRequest
+      }
+      .update(true)
+  }
+
   def updateAssignedUserName(
     owner: String,
     repository: String,
diff --git a/src/main/scala/gitbucket/core/service/LabelsService.scala b/src/main/scala/gitbucket/core/service/LabelsService.scala
index 4bbd5d8..a0f7dc8 100644
--- a/src/main/scala/gitbucket/core/service/LabelsService.scala
+++ b/src/main/scala/gitbucket/core/service/LabelsService.scala
@@ -3,6 +3,7 @@
 import gitbucket.core.model.Label
 import gitbucket.core.model.Profile._
 import gitbucket.core.model.Profile.profile.blockingApi._
+import gitbucket.core.util.StringUtil
 
 trait LabelsService {
 
@@ -24,6 +25,11 @@
     )
   }
 
+  def createLabel(owner: String, repository: String, labelName: String)(implicit s: Session): Int = {
+    val color = StringUtil.md5(labelName).substring(0, 6)
+    createLabel(owner, repository, labelName, color)
+  }
+
   def updateLabel(owner: String, repository: String, labelId: Int, labelName: String, color: String)(
     implicit s: Session
   ): Unit =
diff --git a/src/main/scala/gitbucket/core/service/PullRequestService.scala b/src/main/scala/gitbucket/core/service/PullRequestService.scala
index 09d2552..185955c 100644
--- a/src/main/scala/gitbucket/core/service/PullRequestService.scala
+++ b/src/main/scala/gitbucket/core/service/PullRequestService.scala
@@ -4,6 +4,7 @@
 import gitbucket.core.model.Profile._
 import gitbucket.core.model.Profile.profile.blockingApi._
 import difflib.{Delta, DiffUtils}
+import gitbucket.core.service.RepositoryService.RepositoryInfo
 import gitbucket.core.api.JsonFormat
 import gitbucket.core.util.SyntaxSugars._
 import gitbucket.core.util.Directory._
@@ -14,6 +15,7 @@
 import gitbucket.core.view
 import gitbucket.core.view.helpers
 import org.eclipse.jgit.api.Git
+import org.eclipse.jgit.lib.ObjectId
 
 import scala.collection.JavaConverters._
 
@@ -399,6 +401,58 @@
     updateClosed(owner, repository, pull.issueId, true)
   }
 
+  /**
+   * Parses branch identifier and extracts owner and branch name as tuple.
+   *
+   * - "owner:branch" to ("owner", "branch")
+   * - "branch" to ("defaultOwner", "branch")
+   */
+  def parseCompareIdentifier(value: String, defaultOwner: String): (String, String) =
+    if (value.contains(':')) {
+      val array = value.split(":")
+      (array(0), array(1))
+    } else {
+      (defaultOwner, value)
+    }
+
+  def getPullRequestCommitFromTo(
+    originRepository: RepositoryInfo,
+    forkedRepository: RepositoryInfo,
+    originId: String,
+    forkedId: String
+  ): (Option[ObjectId], Option[ObjectId]) = {
+    using(
+      Git.open(getRepositoryDir(originRepository.owner, originRepository.name)),
+      Git.open(getRepositoryDir(forkedRepository.owner, forkedRepository.name))
+    ) {
+      case (oldGit, newGit) =>
+        if (originRepository.branchList.contains(originId)) {
+          val forkedId2 =
+            forkedRepository.tags.collectFirst { case x if x.name == forkedId => x.id }.getOrElse(forkedId)
+
+          val originId2 = JGitUtil.getForkedCommitId(
+            oldGit,
+            newGit,
+            originRepository.owner,
+            originRepository.name,
+            originId,
+            forkedRepository.owner,
+            forkedRepository.name,
+            forkedId2
+          )
+
+          (Option(oldGit.getRepository.resolve(originId2)), Option(newGit.getRepository.resolve(forkedId2)))
+
+        } else {
+          val originId2 =
+            originRepository.tags.collectFirst { case x if x.name == originId => x.id }.getOrElse(originId)
+          val forkedId2 =
+            forkedRepository.tags.collectFirst { case x if x.name == forkedId => x.id }.getOrElse(forkedId)
+
+          (Option(oldGit.getRepository.resolve(originId2)), Option(newGit.getRepository.resolve(forkedId2)))
+        }
+    }
+  }
 }
 
 object PullRequestService {
diff --git a/src/main/scala/gitbucket/core/service/RepositoryService.scala b/src/main/scala/gitbucket/core/service/RepositoryService.scala
index d784291..2f152db 100644
--- a/src/main/scala/gitbucket/core/service/RepositoryService.scala
+++ b/src/main/scala/gitbucket/core/service/RepositoryService.scala
@@ -621,6 +621,14 @@
     Collaborators insert Collaborator(userName, repositoryName, collaboratorName, role)
 
   /**
+   * Remove specified collaborator from the repository.
+   */
+  def removeCollaborator(userName: String, repositoryName: String, collaboratorName: String)(
+    implicit s: Session
+  ): Unit =
+    Collaborators.filter(_.byPrimaryKey(userName, repositoryName, collaboratorName)).delete
+
+  /**
    * Remove all collaborators from the repository.
    */
   def removeCollaborators(userName: String, repositoryName: String)(implicit s: Session): Unit =