Added migrate_issue to labhub plugin

Closes coala#518

plugins/labhub.py

@@ -381,3 +381,88 @@ def pr_stats(self, msg, match):
                     state=type(self).community_state(pr_count)
                  )
         yield reply
+
+
+    @re_botcmd(pattern=r'^migrate\s+https://(github|gitlab)\.com/([^/]+)/([^/]+)/+issues/(\d+)\s+https://(github|gitlab)\.com/([^/]+)/([^/]+)/*$',  # Ignore LineLengthBear, PyCodeStyleBear
+               re_cmd_name_help='migrate <complete-issue-URL-to-be-copied-from> <complete-repo-URL-to-be-copied-into>',  # Ignore LineLengthBear, PyCodeStyleBear
+               flags=re.IGNORECASE)
+    def migrate_issue(self, msg, match):
+        """Migrate an issue from one repo
+           to another repo of coala"""  # Ignore QuotesBear    
+        org = match.group(2)
+        repo_name_orig = match.group(3)
+        issue_number = match.group(4)
+        org2 = match.group(6)
+        try:
+            assert org == self.GH_ORG_NAME or org == self.GL_ORG_NAME
+        except AssertionError:
+            yield 'First repository not owned by our org.'
+            return
+
+        try:
+            assert org2 == self.GH_ORG_NAME or org2 == self.GL_ORG_NAME
+        except AssertionError:
+            yield 'Second repository not owned by our org.'
+            return
+
+        repo_name_final = match.group(7)
+
+        if repo_name_orig in self.REPOS and repo_name_final in self.REPOS:
+            pass
+        else:
+            return tenv().get_template(
+                'labhub/errors/no-repository.jinja2.md'
+            ).render(
+                target=user,
+            )
+
+        user = msg.frm.nick
+        if self.TEAMS[self.GH_ORG_NAME + ' maintainers'].is_member(user):
+            pass
+        else:
+            return tenv().get_template(
+                'labhub/errors/not-maintainer.jinja2.md'
+            ).render(
+                action='migrate issues',
+                target=user,
+            )
+
+        try:
+            old_issue = self.REPOS[repo_name_orig].get_issue(int(issue_number))
+        except KeyError:
+            return 'Issue doesn\'t exist.'
+
+        if old_issue.is_closed():
+            return 'Issue cannot be migrated as it has been closed already.'
+        else:
+            pass
+
+        old_issue.add_labels('Invalid')
+
+        new_issue_title = str(old_issue.title)
+        new_issue_description = str(old_issue.body).rstrip()
+        extra_msg = '\n\nMigrated issue from '+old_issue.html_url
+        extra_msg += ' by @'+user
+        new_issue = self.REPOS[repo_name_final].create_issue(new_issue_title, new_issue_description + extra_msg) # Ignore LineLengthBear, PyCodeStyleBear
+
+        new_issue.add_labels(old_issue.labels)
+
+        old_comments_iter = old_issue.iter_comments()
+        while(True):
+            try:
+                com = old_comments_iter.next()
+                auth = com.user
+                url = com.html_url
+		old_body = com.body
+                update_dt = com.updated_at
+                new_body = old_body.rstrip()+'\n\nOriginally written by @'+auth+' on '+str(update_dt) # Ignore LineLengthBear, PyCodeStyleBear
+		new_body += ' and you can view it [here!]('+url+')'
+                new_issue.create_comment(new_body) 
+            except StopIteration:
+                break
+
+        msg_to_old_repo = '\n\nIssue has been migrated to another [repository here!]('+new_issue.html_url+') by @'+user+'.' # Ignore LineLengthBear, PyCodeStyleBear
+        edited_body = str(old_issue.body).rstip()+msg_to_old_repo
+        old_issue.edit(body=edited_body)
+        old_issue.close()
+