Fixed in the rebase.

QA verified this bug with libguestfs-1.7.17-12.el6.x86_64 and guestfish-1.7.17-12.el6.x86_64:

# guestfish
><fs> alloc test.img 1000M
><fs> add test.img
><fs> run
><fs> mkfs ext2 /dev/vda
><fs> vfs-type /dev/vda
ext2
><fs> mkfs vfat /dev/vda
><fs> vfs-type /dev/vda
vfat


So change this bug to VERIFIED.

    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
The guestfish vfs-type command could not determine the type of a file system newly created by guestfish. This occurred because the vfs-type command tried to read the type from a cache file (blkid.c) that had not yet been updated. The cache file is now deleted between file system creation and attempting to read the file system type, forcing vfs-type to read updated file system information.

    Technical note updated. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    Diffed Contents:
@@ -1 +1 @@
-The guestfish vfs-type command could not determine the type of a file system newly created by guestfish. This occurred because the vfs-type command tried to read the type from a cache file (blkid.c) that had not yet been updated. The cache file is now deleted between file system creation and attempting to read the file system type, forcing vfs-type to read updated file system information.+The guestfish vfs-type command could not determine the type of a file system newly created by guestfish. This occurred because the vfs-type command tried to read the type from a cache file (blkid.c) that had not yet been updated. The cache file is now deleted between file system creation and attempting to read the file system type, resulting in updated file system information for vfs-type to read

This is fine, thanks.

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0586.html

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0586.html