git-find-blob

#!/bin/sh

filename=$1

want=$(git hash-object "$filename")

git rev-list --since="6 months ago" HEAD | while read -r commit ; do
    git ls-tree -r "$commit" | while read -r perm type hash filename; do
        if test "$want" = "$hash"; then
            echo "matched $filename in commit $commit"
        fi
    done
done