[FIX] runbot: dont duplicate export

Even if it isn't really problematic, avoiding to duplicate exports
will make the table slighly smaller, especially when considering running
builds.

runbot/models/build.py

@@ -329,6 +329,8 @@ def write(self, values):
             build_by_old_values = defaultdict(lambda: self.env['runbot.build'])
             for record in self:
                 build_by_old_values[record.local_state] += record
+            if values['local_state'] == 'done':
+                self.env['runbot.commit.export'].search([('build_id', 'in', self.ids)]).unlink()
         local_result = values.get('local_result')
         for build in self:
             if local_result and local_result != self._get_worst_result([build.local_result, local_result]):  # dont write ok on a warn/error build
@@ -729,8 +731,6 @@ def _schedule(self):
                 build._github_status()
             build._run_job()
 
-            if build.local_state == 'done':
-                self.env['runbot.commit.export'].search([('build_id', '=', build.id)]).unlink()
 
     def _run_job(self):
         # run job

runbot/models/commit.py

@@ -56,7 +56,8 @@ def export(self, build):
         """Export a git repo into a sources"""
         #  TODO add automated tests
         self.ensure_one()
-        self.env['runbot.commit.export'].create({'commit_id': self.id, 'build_id': build.id})
+        if not self.env['runbot.commit.export'].search([('build_id', '=', build.id), ('commit_id', '=', self.id)]):
+            self.env['runbot.commit.export'].create({'commit_id': self.id, 'build_id': build.id})
         export_path = self._source_path()
 
         if os.path.isdir(export_path):