git-http-fetch Segmentation fault

 Hi,

 A friend of mine reported an easy to reproduce segmentation fault
when cloning through http from his repository:

""" ~/ git clone http://people.mandriva.com/~boiko/mandrivamenu.git got 299cdadd846913a052df361e973a947622f23198 walk 299cdadd846913a052df361e973a947622f23198 ... got 0ecd10d9d6ab020c2469a961777854afda705776 /home/lcapitulino/git//bin/git-clone: line 33: 22353 Segmentation fault (core dumped) git-http-fetch $v -a -w "$tname" "$sha1" "$1" """

 Sometimes it shows up as a corrupted double-linked list, detected by
glibc:

""" *** glibc detected *** git-http-fetch: corrupted double-linked list: 0x080a5680 *** """

 It's reproducible with Junio's master and maint branches (3082ac and
53a582 respectivelly).

 BTW, At line 406 (the trap command), git-clone script removes the
directory it was fetching. This removes the core dump file too.
We should not remove the directory if there's a core dump in there.