Duh! How do I apply memleak patch to 2.1P2?

This is a REALLY stupid question. Please keep flames below 200° Celsius.
:)

Which directory has to be the current before I run

patch < squid-2.1.PATCH2-clientHandleIMSReply-leak.patch

And do I need a modifier like -p0 or -p1 or anything like that?

[]'s,

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