snapshot: Delete All should skip currently active snapshot

Delete All in case of rollbacks was failing because it cannot delete the
snapshot that's active. This has to be skipped and the remaining snapshots
deleted.

Also, the active snapshot won't be listed in the form to delete all snapshots.

Signed-off-by: Joseph Nuthalapati <njoseph@thoughtworks.com>
Reviewed-by: Sunil Mohan Adapa <sunil@medhas.org>

actions/snapshot

@@ -156,16 +156,32 @@ def subcommand_delete(arguments):
 
 
 def subcommand_delete_all(_):
-    """Delete all the snapshots."""
+    """Delete all the snapshots (except the active one)."""
     lines = _get_snapper_list()
     snapshot_range = [line.split('|')[1].strip() for line in lines[3:]]
+    default_snapshot = _get_default_snapshot()
     if snapshot_range:
-        if len(snapshot_range) == 1:
-            to_delete = snapshot_range[0]
+        if default_snapshot:
+            index = snapshot_range.index(default_snapshot)
+            range_before = snapshot_range[:index]
+            range_after = snapshot_range[index + 1:]
+            to_delete = [range_before, range_after]
         else:
-            to_delete = '-'.join([snapshot_range[0], snapshot_range[-1]])
-        command = ['snapper', 'delete', to_delete]
-        subprocess.run(command, check=True)
+            to_delete = [snapshot_range]
+
+        delete_args = filter(None, map(_get_delete_arg, to_delete))
+        for arg in delete_args:
+            subprocess.run(['snapper', 'delete', arg], check=True)
+
+
+def _get_delete_arg(range_list):
+    """Return 'a-b' when given ['a', ..., 'b']."""
+    if not range_list:
+        return None
+    elif len(range_list) == 1:
+        return range_list[0]
+    else:
+        return range_list[0] + '-' + range_list[-1]
 
 
 def subcommand_configure(arguments):

plinth/modules/snapshot/templates/snapshot_delete_all.html

@@ -36,11 +36,13 @@
         </thead>
         <tbody>
           {% for snapshot in snapshots %}
-          <tr>
-            <td>{{ snapshot.number }}</td>
-            <td>{{ snapshot.date }}</td>
-            <td>{{ snapshot.description }}</td>
-          </tr>
+            {% if not snapshot.is_default %}
+              <tr>
+                <td>{{ snapshot.number }}</td>
+                <td>{{ snapshot.date }}</td>
+                <td>{{ snapshot.description }}</td>
+              </tr>
+            {% endif %}
           {% endfor %}
         </tbody>
       </table>