Code reuse

Hey guys

I am not sure if this is the right place to ask this question, but
I've been working on a personal project a programming language
interpreter for some time now, but i took 2 code snippets from
git-core namely:

static struct hash_table_entry *lookup_hash_entry(unsigned int hash,
const struct hash_table *table)

function from hash.c and the alloc_nr.

I've changed it a good bit (probably doesn't resemble much of what it
was) to fit in with the way my stuff works but is there anything i
need to like put in my source code to say hey this is based of
git-core, so far is just a comment to say 'based of git-core hash.c'.
Its an open source (GPL) program but i haven't released or made much
noise about it yet because i want to work on it more myself.

Anyways thanks,

--Phil