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>

routers/web/org/home.go

@@ -40,6 +40,7 @@ func Home(ctx *context.Context) {
 	ctx.Data["Title"] = org.DisplayName()
 	if len(org.Description) != 0 {
 		desc, err := markdown.RenderString(&markup.RenderContext{
+			Ctx:       ctx,
 			URLPrefix: ctx.Repo.RepoLink,
 			Metas:     map[string]string{"mode": "document"},
 			GitRepo:   ctx.Repo.GitRepo,