[tools] testbot/LibvirtTool: Allow using preconfigured non-live snapshots as a base.

[Francois Gouget]

Don't use 'test-live' as a base because we cannot assume that rebooting
it will not break its configuration. But do use snapshots such as
'test-adm' as a base. This allows automating the creation of live
snapshots for Windows versions where a given option is not supported.

Signed-off-by: Francois Gouget <fgouget(a)codeweavers.com>
---
Such as the adm option on Windows 7.
---
 testbot/bin/LibvirtTool.pl | 41 ++++++++++++++++++++++----------------
 1 file changed, 24 insertions(+), 17 deletions(-)

diff --git a/testbot/bin/LibvirtTool.pl b/testbot/bin/LibvirtTool.pl
index df7859dea..a9622de7d 100755
--- a/testbot/bin/LibvirtTool.pl
+++ b/testbot/bin/LibvirtTool.pl
@@ -613,27 +613,34 @@ sub PrepareVM($)
   }
 }
 
-sub GetSnapshotConfig($)
+sub GetSnapshotConfig($$)
 {
-  my ($Config) = @_;
-
-  # Don't stack snapshots. For instance assume the snapshot name is
-  # 'test-live-fr-FR-tsign' and that 'test-live-fr-FR' already exists
-  # (typically because it is used by another VM):
-  # - It's probably better if snapshots are independent from each other.
-  # - Applying the 'tsign' flag on top of the existing snapshot requires a
-  #   Windows reboot. But format locale changes may not stick across reboots.
-  # - Stopping the snapshot name parsing when finding an existing snapshot name
-  #   would lose the 'live' flag resulting in an error (or the wrong type of
-  #   snapshot. Avoiding this issue would result in more complexity.
-  # - Finally snapshot stacking does not seem that useful.
-  # - A consequence is that the base snapshot should be called 'test' and not
-  #   'test-live'.
+  my ($Domain, $Config) = @_;
+
+  # Notes:
+  # - Don't use a live snapshot as a base snapshot:
+  #   - It's probably better if snapshots are independent from each other.
+  #   - Applying extra options on top of a live snapshot may require a reboot.
+  #     But some locales changes may not survive that. So using, for instance,
+  #     test-fr-FR-live as a base may break the locale.
+  # - However some options are not supported on all Windows versions. For
+  #   instance 'adm' snapshots cannot be created on Windows 7 so in that case
+  #   it is useful to be able to use a preconfigured test-adm as a base
+  #   snapshot for test-adm-live.
+  # - Finally, although base snapshots, such as 'test', are presumably powered
+  #   off, 'off' snapshots still create a new snapshot. The difference is that
+  #   the 'test-off' snapshot will have an up-to-date TestAgentd server, the
+  #   right desktop background, etc.
   while (1)
   {
+    if ($Config->{base} !~ /-live\b/ and
+        $Domain->HasSnapshot($Config->{base}))
+    {
+      last;
+    }
     if ($Config->{base} =~ s/-([a-z]{2}-[A-Z]{2})$//)
     {
-      $Config->{locale} ||= $1; # take only the last match
+      $Config->{locale} ||= $1; # use the last locale in the snapshot name
     }
     elsif ($Config->{base} =~ s/-(adm|live|off|tsign|u8)$//)
     {
@@ -837,7 +844,7 @@ sub Revert()
   if (!$Domain->HasSnapshot($Config->{base}))
   {
     $Config->{create} = 1;
-    GetSnapshotConfig($Config);
+    GetSnapshotConfig($Domain, $Config);
     Debug(join(" ", Elapsed($Start), "Config:", map { "$_=$Config->{$_}" } sort keys %$Config), "\n");
     if ($Config->{locale} and $VM->Type !~ /^win(?:32|64)$/)
     {
-- 
2.30.2