Refactor request context (#32956)

Introduce RequestContext: is a short-lived context that is used to store
request-specific data.

RequestContext could be used to clean form tmp files, close context git
repo, and do some tracing in the future.

Then a lot of legacy code could be removed or improved. For example:
most `ctx.Repo.GitRepo.Close()` could be removed because the git repo
could be closed when the request is done.

routers/private/internal_repo.go

@@ -4,7 +4,6 @@
 package private
 
 import (
-	"context"
 	"fmt"
 	"net/http"
 
@@ -17,40 +16,29 @@ import (
 
 // This file contains common functions relating to setting the Repository for the internal routes
 
-// RepoAssignment assigns the repository and gitrepository to the private context
-func RepoAssignment(ctx *gitea_context.PrivateContext) context.CancelFunc {
+// RepoAssignment assigns the repository and git repository to the private context
+func RepoAssignment(ctx *gitea_context.PrivateContext) {
 	ownerName := ctx.PathParam(":owner")
 	repoName := ctx.PathParam(":repo")
 
 	repo := loadRepository(ctx, ownerName, repoName)
 	if ctx.Written() {
 		// Error handled in loadRepository
-		return nil
+		return
 	}
 
-	gitRepo, err := gitrepo.OpenRepository(ctx, repo)
+	gitRepo, err := gitrepo.RepositoryFromRequestContextOrOpen(ctx, ctx, repo)
 	if err != nil {
 		log.Error("Failed to open repository: %s/%s Error: %v", ownerName, repoName, err)
 		ctx.JSON(http.StatusInternalServerError, private.Response{
 			Err: fmt.Sprintf("Failed to open repository: %s/%s Error: %v", ownerName, repoName, err),
 		})
-		return nil
+		return
 	}
-
 	ctx.Repo = &gitea_context.Repository{
 		Repository: repo,
 		GitRepo:    gitRepo,
 	}
-
-	// We opened it, we should close it
-	cancel := func() {
-		// If it's been set to nil then assume someone else has closed it.
-		if ctx.Repo.GitRepo != nil {
-			ctx.Repo.GitRepo.Close()
-		}
-	}
-
-	return cancel
 }
 
 func loadRepository(ctx *gitea_context.PrivateContext, ownerName, repoName string) *repo_model.Repository {