SIGPIPE in t9300-fast-import

The new cat-blob test (9300.114) is failing for me on OS X, and has been since it's introduction in "85c6239 fast-import: let importers retrieve blobs":

---- 8< ----

ok 113 - setup: have pipes?

expecting success: 
	expect_id=$(git hash-object big) &&
	expect_len=$(wc -c <big) &&
	echo $expect_id blob $expect_len >expect.response &&

	rm -f blobs &&
	cat >frontend <<-\FRONTEND_END &&
	#!/bin/sh
	cat <<EOF &&
	feature cat-blob
	blob
	mark :1
	data <<BLOB
	EOF
	cat big
	cat <<EOF
	BLOB
	cat-blob :1
	EOF

	read blob_id type size <&3 &&
	echo "$blob_id $type $size" >response &&
	dd of=blob bs=$size count=1 <&3 &&
	read newline <&3 &&

	cat <<EOF &&
	commit refs/heads/copied
	committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
	data <<COMMIT
	copy big file as file3
	COMMIT
	M 644 inline file3
	data <<BLOB
	EOF
	cat blob &&
	cat <<EOF
	BLOB
	EOF
	FRONTEND_END

	mkfifo blobs &&
	(
		export GIT_COMMITTER_NAME GIT_COMMITTER_EMAIL GIT_COMMITTER_DATE &&
		sh frontend 3<blobs |
		git fast-import --cat-blob-fd=3 3>blobs
	) &&
	git show copied:file3 >actual &&
	test_cmp expect.response response &&
	test_cmp big actual

0+1 records in 0+1 records out 8139 bytes transferred in 0.000062 secs (131297847 bytes/sec) error: git-fast-import died of signal 13 not ok - 114 R: copy using cat-file ---- 8< ----

I don't have the tuits right now to dig into this, but "trash directory.t9300-fast-input" has a good response (`cmp expect.response response` is true), but has no refs/heads/copied.  I can run help provide diagnostics, if anyone needs more data.

~~ Brian

PS:  Isn't t9300 getting a little crazily long?  Is there a good way to split it up by feature or something? It runs quickly, but finding were something is failing is getting a little difficult.