[IMP] runbot_merge: a few backend screens

- override the staging's name_get to provide a slightly more useful
  display_name (though still not great as the staging object remains
  quite technical and inimical to human interaction)
- show individual PRs in a batch (as m2m tags) for readability
- update PR views to show the author and reviewer, except in the list
  of delegations of users where it's a lot less useful

/cc #632

runbot_merge/models/pull_requests.py

@@ -1683,6 +1683,17 @@ class Stagings(models.Model):
 
     statuses = fields.Binary(compute='_compute_statuses')
 
+    def name_get(self):
+        return [
+            (staging.id, "%d (%s, %s%s)" % (
+                staging.id,
+                staging.target.name,
+                staging.state,
+                (', ' + staging.reason) if staging.reason else '',
+            ))
+            for staging in self
+        ]
+
     @api.depends('heads')
     def _compute_statuses(self):
         """ Fetches statuses associated with the various heads, returned as

runbot_merge/views/mergebot.xml

@@ -77,6 +77,8 @@
                 <field name="number"/>
                 <field name="target"/>
                 <field name="state"/>
+                <field name="author"/>
+                <field name="reviewed_by"/>
             </tree>
         </field>
     </record>
@@ -198,7 +200,8 @@
                     <group string="Batches">
                         <field name="batch_ids" colspan="4" nolabel="1">
                             <tree>
-                                <field name="prs"/>
+                                <field name="prs" widget="many2many_tags"
+                                       options="{'no_quick_create': True}"/>
                             </tree>
                         </field>
                     </group>

runbot_merge/views/res_partner.xml

@@ -70,7 +70,14 @@
                     </group>
                     <group>
                         <group colspan="4" string="Delegate On">
-                            <field name="delegate_reviewer" nolabel="1"/>
+                            <field name="delegate_reviewer" nolabel="1">
+                                <tree>
+                                    <field name="repository"/>
+                                    <field name="number"/>
+                                    <field name="target"/>
+                                    <field name="state"/>
+                                </tree>
+                            </field>
                         </group>
                     </group>
                 </page>