Propagate context and ensure git commands run in request context (#17868)

This PR continues the work in #17125 by progressively ensuring that git
commands run within the request context.

This now means that the if there is a git repo already open in the context it will be used instead of reopening it.

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

modules/doctor/checkOldArchives.go

@@ -5,6 +5,7 @@
 package doctor
 
 import (
+	"context"
 	"os"
 	"path/filepath"
 
@@ -13,7 +14,7 @@ import (
 	"code.gitea.io/gitea/modules/util"
 )
 
-func checkOldArchives(logger log.Logger, autofix bool) error {
+func checkOldArchives(ctx context.Context, logger log.Logger, autofix bool) error {
 	numRepos := 0
 	numReposUpdated := 0
 	err := iterateRepositories(func(repo *repo_model.Repository) error {