This PR migrates temp_repo.go to use git.NewCommand instead creating processes by itself - this fixes the problem underlying PR #8905.

There are other places that run git outside of the controlled locale defined in #8548 but temp_repo.go is the only cause of failure of local testing in cases where English is not the default - implying that error messages from those other commands are not interpreted.

Replaces #8905

There are two major components to this PR:

* This PR handles merge and rebase failures from merging a little more nicely with Flash errors rather a 500.
* All git commands are run in the LC_ALL="C" environment to ensure that error messages are in English. This DefaultLocale is defined in a way that if necessary (due to platform weirdness) it can be overridden at build time using LDFLAGS="-X "code.gitea.io/gitea/modules/git.DefaultLocale=C"" with C changed for the locale as necessary.

* monitor all git commands; move blame to git package and replace git as a variable

* use git command but not other commands

* fix build

* move exec.Command to git.NewCommand

* fix fmt

* remove unrelated changes

* remove unrelated changes

* refactor IsEmpty and add tests

* fix tests

* fix tests

* fix tests

* fix tests

* remove gitLogger

* fix fmt

* fix isEmpty

* fix lint

* fix tests

* Add options to git.Clone to make it more capable

* Begin the process of removing the local copy and tidy up

* Remove Wiki LocalCopy Checkouts

* Remove the last LocalRepo helpers

* Remove WithTemporaryFile

* Enable push-hooks for these routes

* Ensure tests cope with hooks

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

* Remove Repository.LocalCopyPath()

* Move temporary repo to use the standard temporary path

* Fix the tests

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

* Remove LocalWikiPath

* Fix missing remove

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

* Use AppURL for Oauth user link (#6894)

* Use AppURL for Oauth user link

Fix #6843

* Update oauth.go

* Update oauth.go

* internal/ssh: ignore env command totally (#6825)

* ssh: ignore env command totally

* Remove commented code 

Needed fix described in issue #6889

* Escape the commit message on issues update and title in telegram hook (#6901)

* update sdk to latest (#6903)

* improve description of branch protection (fix #6886) (#6906)

The branch protection description text were not quite accurate.

* Fix logging documentation (#6904)

* ENABLE_MACARON_REDIRECT should be REDIRECT_MACARON_LOG

* Allow DISABLE_ROUTER_LOG to be set in the [log] section

* [skip ci] Updated translations via Crowdin

* Move sdk structs to modules/structs (#6905)

* move sdk structs to moduels/structs

* fix tests

* fix fmt

* fix swagger

* fix vendor

* Pre-caculate the absolute path of git

* Do not repeat string literals which has been defined somewhere

Also make it flexible to accept customized/user-defined value.

* move code.gitea.io/git to code.gitea.io/gitea/modules/git

* fix imports

* fix fmt

* fix misspell

* remove wrong tests data

* fix unit tests

* fix tests

* fix tests

* fix tests

* fix tests

* fix tests

* enable Debug to trace the failure tests

* fix tests

* fix tests

* fix tests

* fix tests

* fix tests

* comment commit count tests since git clone depth is 50

* fix tests

* update from code.gitea.io/git

* revert change to makefile