Refactor git module, make Gitea use internal git config (#19732)

* Refactor git module, make Gitea use internal git config, add safe.directory config

* introduce git.InitSimple and git.InitWithConfigSync, make serv cmd use gitconfig

* use HOME instead of GIT_CONFIG_GLOBAL, because git always needs a correct HOME

* fix cmd env in cmd/serv.go

* fine tune error message

* Fix a incorrect test case

* fix configAddNonExist

* fix configAddNonExist logic, add `--fixed-value` flag, add tests

* add configSetNonExist function in case it's needed.

* use configSetNonExist for `user.name` and `user.email`

* add some comments

* Update cmd/serv.go

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

* Update cmd/serv.go

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

* Update modules/git/git.go

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

* Update modules/setting/setting.go

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

* Update modules/git/repo_attribute.go

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

* fix spaces in messages

* use `configSet("core.protectNTFS", ...)` instead of `globalCommandArgs`

* remove GIT_CONFIG_NOSYSTEM, continue to use system's git config

* Update cmd/serv.go

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

* fix merge

* remove code for safe.directory

* separate git.CommonEnvs to CommonGitCmdEnvs and CommonCmdServEnvs

* avoid Golang's data race error

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

routers/init.go

@@ -102,8 +102,8 @@ func GlobalInitInstalled(ctx context.Context) {
 		log.Fatal("Gitea is not installed")
 	}
 
-	mustInitCtx(ctx, git.Init)
-	log.Info(git.VersionInfo())
+	mustInitCtx(ctx, git.InitWithConfigSync)
+	log.Info("Git Version: %s (home: %s)", git.VersionInfo(), git.HomeDir())
 
 	git.CheckLFSVersion()
 	log.Info("AppPath: %s", setting.AppPath)