Reject paths given to --filesystem/--persist with special characters

There isn't much in the way of legit reasons for this, but it's a
potential security footgun when displaying the text.

CVE-2023-28101, GHSA-h43h-fwqx-mpp8

Signed-off-by: Ryan Gonzalez <ryan.gonzalez@collabora.com>
Co-authored-by: Simon McVittie <smcv@collabora.com>
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f