launch: Store drive information in guestfs_h

This is a NFC on its own, but provides a place-holder for drive metadata which
can be used after launch.

Fixes by RWMJ:

 - Fix the tests: this requires a new internal function 'debug-drives'
   that dumps out the g->drives information so it can be checked in
   two of the tests.  Previously these tests used 'debug-cmdline'.

 - Test file existence / use_cache_off in the add_drive_opts function,
   not when launching qemu in the child process.

 - Call free along error paths.

 - Add comments.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/virt.c b/src/virt.c
index 58cb999d..cc11c68a 100644
--- a/src/virt.c
+++ b/src/virt.c
@@ -392,10 +392,10 @@ guestfs___add_libvirt_dom (guestfs_h *g, virDomainPtr dom,
   /* Checkpoint the command line around the operation so that either
    * all disks are added or none are added.
    */
-  cmdline_pos = guestfs___checkpoint_cmdline (g);
+  struct drive **cp = guestfs___checkpoint_drives (g);
   r = guestfs___for_each_disk (g, dom, add_disk, &optargs2);
   if (r == -1)
-    guestfs___rollback_cmdline (g, cmdline_pos);
+    guestfs___rollback_drives (g, cp);
 
   return r;
 }