Better way to find commit from tarball?

Someone handed me a tarball that represented an unknown release from a
project. Here's what I came up with to identify the commit:

    cd $SOME_WORK_DIR
    find . -path ./.git -prune -o -print0 | xargs -0 rm
    tar xvfz $TARBALL
    for commit in {0..100}; do
        id="master~${commit}"
        if git diff --quiet --exit-code "$id"
        then
            echo "Matched on commit $id"
            break
        fi
    done

Someone please tell me there's an easier way to find a matching tree
when handed a tarball. This works, but seems cumbersome.

Todd A. Jacobs wrote:

    cd $SOME_WORK_DIR
    find . -path ./.git -prune -o -print0 | xargs -0 rm
    tar xvfz $TARBALL
    for commit in {0..100}; do
        id="master~${commit}"
        if git diff --quiet --exit-code "$id"
        then
            echo "Matched on commit $id"
            break
        fi
    done

Someone please tell me there's an easier way to find a matching tree
when handed a tarball. This works, but seems cumbersome.

If you are lucky and they used "git archive":

	gunzip <$TARBALL | git get-tar-commit-id

Otherwise: maybe something like this[1] will work.

	tar_id=$(
		git init tarball &&
		cd tarball &&
		perl /usr/share/doc/git/contrib/fast-import/import-tars.perl $TARBALL &&
		git rev-parse --verify HEAD:
	) &&
	rm -fr tarball &&
	git rev-list --full-history --format='%h %T' HEAD |
	grep " $tar_id\$"

[1] http://thread.gmane.org/gmane.comp.version-control.git/44750/focus=44849