git test failure: t9903-bash-prompt.sh on darwin8

Hi,
 	I'm seeing a test failure with git-1.8.4 on powerpc-darwin8:

[11:00:56] t9903-bash-prompt.sh ............................... not ok 13 - prompt - interactive rebase not ok 14 - prompt - rebase merge

Details here:

http://paste.lisp.org/display/139525

The odd thing is that when I run the test t9903 interactively, post-mortem, it passes -- I am unable to reproduce the failure outside of the unprivileged build environment. Interactively, the test always passes regardless of my interaction shell: csh, sh-2.0, bash-4.2. (Noninteractive test happens to use bash-2.0.)

So I force the test to halt immediately upon failure to examine the temporary trash directory, and the difference between actual/expected:

http://paste.lisp.org/display/139525#4

What could cause the results to differ between by interactive and non-interactive testing of t9903? Is there a real problem?

Fang