* git: delegate all server-side Git hooks (#1623)

* create hooks directories

* take control hooks back

* fix lint

* bug fixed and minor changes

* fix imports style

* fix migration scripts

Fix lint errors

* refactor for issues loadattributes of a repository

* refactors

* fix: Wrong repo list on Explore page if user already loggin.

* fix: code readable.

* fix: declare variable

* initial stuff for oauth2 login, fails on:
* login button on the signIn page to start the OAuth2 flow and a callback for each provider
Only GitHub is implemented for now
* show login button only when the OAuth2 consumer is configured (and activated)
* create macaron group for oauth2 urls
* prevent net/http in modules (other then oauth2)
* use a new data sessions oauth2 folder for storing the oauth2 session data
* add missing 2FA when this is enabled on the user
* add password option for OAuth2 user , for use with git over http and login to the GUI
* add tip for registering a GitHub OAuth application
* at startup of Gitea register all configured providers and also on adding/deleting of new providers
* custom handling of errors in oauth2 request init + show better tip
* add ExternalLoginUser model and migration script to add it to database
* link a external account to an existing account (still need to handle wrong login and signup) and remove if user is removed
* remove the linked external account from the user his settings
* if user is unknown we allow him to register a new account or link it to some existing account
* sign up with button on signin page (als change OAuth2Provider structure so we can store basic stuff about providers)

* from gorilla/sessions docs:
"Important Note: If you aren't using gorilla/mux, you need to wrap your handlers with context.ClearHandler as or else you will leak memory!"
(we're using gorilla/sessions for storing oauth2 sessions)

* use updated goth lib that now supports getting the OAuth2 user if the AccessToken is still valid instead of re-authenticating (prevent flooding the OAuth2 provider)

* Protected branches system

* Moved default branch to branches section (`:org/:reponame/settings/branches`).
* Initial support Protected Branch.
  - Admin does not restrict
  - Owner not to limit
  - To write permission restrictions

* reformat tmpl

* finished the UI and add/delete protected branch response

* remove unused comment

* indent all the template files and remove ru translations since we use crowdin

* fix the push bug

* make xorm log configable

* bug fixed for other sub commands except web

* rebase and fix xorm log

* bug fix for TrimSpace

Signed-off-by: Andrew Boyarshin <andrew.boyarshin@gmail.com>

Reported by Miguel Ángel Jimeno.

* fix all the bugs in issues and pulls on dashboard

* small fix and refactor

* add method getRepoIDs for IssueList

For `UI`-bugs we usually require a Screenshot to debug it :wink:

* fix: fill in ssh key title on setting of repo

* fix: Don't overwrite ssh key title if exist.

* Small opitimization for getUserTeams

* more compact

Reported by Miguel Ángel Jimeno.

* refactor: small optimize for sql query

* fix: get owner name if Searcher is not nil or user star page.

* Fix assigned/created issues in dashboard. (#3560)

* Fix assigned/created issues in dashboard.

* Use GetUserIssueStats for getting all Dashboard stats.

* Use gofmt to format the file properly.

* Replace &Issue{} with new(Issue).

* Check if user has access to given repository.

* Remove unnecessary filtering of issues.

* Return 404 error if invalid repository is given.

* Use correct number of issues in paginater.

* fix issues on dashboard

* feat: support search bar on star tab of user profile.

* fix: update testing.

* fix: Using loadAttributes

* fix: remove empty line.

* remove LOWER

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* use fingerprint to check instead content for public key

* add fingerprint field for ErrKeyAlreadyExist

* small optimization for getTeamIDs

* rename getOrgTeamIDs to getUserTeamIDs and remove orderby

* Markdown rendering overhaul

Cleaned up and squashed commits into single one.

Signed-off-by: Andrew Boyarshin <boyarshinand@gmail.com>

* Fix markdown API, add markdown module and API tests, improve code coverage

Signed-off-by: Andrew Boyarshin <boyarshinand@gmail.com>

* Add import-styleguide to Contributing.md

Question: should we group all `code.gitea.io`-packages together as local imports? (including `code.gitea.io/sdk` and `code.gitea.io/git` etc)

* reorg

* be specific FFS