* Generate Diff and Patch direct from Pull head

Fix #10932
Also fix "Empty Diff/Patch File when pull is merged"

Closes #10934

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Add tests to ensure that diff does not change

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Ensure diffs and pulls pages work if head branch is deleted too

Signed-off-by: Andrew Thornton <art27@cantab.net>

* remove ReplaceLeft

* remove GetRepositoryByOwnerAndName chainload to models.GetRepositoryByOwnerAndName

* remove CheckUnitUser chainload to models.CheckUnitUser

* remove MakeAssigneeList

* remove DownloadDiff & DownloadPatch -> DownloadDiffOrPatch

* remove GetRandomBytesAsBase64

* remove PushUpdateDeleteTags

* remove GetUserByKeyID
(you still can resolve user by "k, err := GetPublicKeyByID; userID := k.OwnerID")

* remove BasicAuthEncode from struct package -> same function in modules/base/tools !

* remove UserID from api.utils

* remove unused func from structs package

* Add require signed commit for protected branch

* Fix fmt

* Make editor show if they will be signed

* bugfix

* Add basic merge check and better information for CRUD

* linting comment

* Add descriptors to merge signing

* Slight refactor

* Slight improvement to appearances

* Handle Merge API

* manage CRUD API

* Move error to error.go

* Remove fix to delete.go

* prep for merge

* need to tolerate \r\n in message

* check protected branch before trying to load it

* Apply suggestions from code review

Co-Authored-By: guillep2k <18600385+guillep2k@users.noreply.github.com>

* fix commit-reader

Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>

* Add owner_name column for table repository for maintaince reason

* refactor

* Fix tests

* fix test

* fix bug when fork repository

Co-authored-by: zeripath <art27@cantab.net>

* Save patches to temporary files

* Remove SavePatch and generate patches on the fly

* Use ioutil.TempDir

* fixup! Use ioutil.TempDir

* fixup! fixup! Use ioutil.TempDir

* RemoveAll LocalCopyPath() in initIntergrationTest

* Default to status checking on PR creation

* Remove unnecessary set to StatusChecking

* Protect against unable to load repo

* Handle conflicts

* Restore original conflict setting

* In TestPullRequests update status to StatusChecking before running TestPatch