Pull mirror sync ran `git fetch` / `remote update` / `remote prune`
without disabling HTTP redirects. A mirror remote that later starts
redirecting to an otherwise-blocked or internal address could be used as
an SSRF/exfiltration vector on scheduled syncs, bypassing the
allow/block validation applied at migration time.
This sets `http.followRedirects=false` on all three remote-contacting
commands in the pull mirror path, matching the existing guard already
present on the clone path.
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