Utilize Django 1.3 'on_delete' feature on several foreign keys

The most important one here is PROTECT to keep people from making
bone-headed plays and deleting an Arch or Repo and every package along
with it. We can use this in a few other places, as well as some
carefully placed SET_NULL indicators.

Note that nothing here pushes deletion responsibilities down to the
database, although that will probably happen in a future commit.

Signed-off-by: Dan McGee <dan@archlinux.org>

main/models.py

@@ -104,8 +104,10 @@ class Meta:
         verbose_name_plural = 'repos'
 
 class Package(models.Model):
-    repo = models.ForeignKey(Repo, related_name="packages")
-    arch = models.ForeignKey(Arch, related_name="packages")
+    repo = models.ForeignKey(Repo, related_name="packages",
+            on_delete=models.PROTECT)
+    arch = models.ForeignKey(Arch, related_name="packages",
+            on_delete=models.PROTECT)
     pkgname = models.CharField(max_length=255, db_index=True)
     pkgbase = models.CharField(max_length=255, db_index=True)
     pkgver = models.CharField(max_length=255)
@@ -121,7 +123,8 @@ class Package(models.Model):
     last_update = models.DateTimeField(null=True, blank=True)
     files_last_update = models.DateTimeField(null=True, blank=True)
     packager_str = models.CharField(max_length=255)
-    packager = models.ForeignKey(User, null=True)
+    packager = models.ForeignKey(User, null=True,
+            on_delete=models.SET_NULL)
     flag_date = models.DateTimeField(null=True)
 
     objects = PackageManager()
@@ -348,7 +351,7 @@ class Meta:
         db_table = 'package_depends'
 
 class Todolist(models.Model):
-    creator = models.ForeignKey(User)
+    creator = models.ForeignKey(User, on_delete=models.PROTECT)
     name = models.CharField(max_length=255)
     description = models.TextField()
     date_added = models.DateTimeField(db_index=True)

mirrors/models.py

@@ -14,7 +14,7 @@
 class Mirror(models.Model):
     name = models.CharField(max_length=255, unique=True)
     tier = models.SmallIntegerField(default=2, choices=TIER_CHOICES)
-    upstream = models.ForeignKey('self', null=True)
+    upstream = models.ForeignKey('self', null=True, on_delete=models.SET_NULL)
     country = models.CharField(max_length=255, db_index=True)
     admin_email = models.EmailField(max_length=255, blank=True)
     public = models.BooleanField(default=True)
@@ -56,7 +56,7 @@ class Meta:
 class MirrorUrl(models.Model):
     url = models.CharField(max_length=255, unique=True)
     protocol = models.ForeignKey(MirrorProtocol, related_name="urls",
-            editable=False)
+            editable=False, on_delete=models.PROTECT)
     mirror = models.ForeignKey(Mirror, related_name="urls")
     has_ipv4 = models.BooleanField("IPv4 capable", default=True,
             editable=False)

news/models.py

@@ -6,7 +6,8 @@
 
 class News(models.Model):
     slug = models.SlugField(max_length=255, unique=True)
-    author = models.ForeignKey(User, related_name='news_author')
+    author = models.ForeignKey(User, related_name='news_author',
+            on_delete=models.PROTECT)
     postdate = models.DateTimeField("post date", db_index=True)
     last_modified = models.DateTimeField(editable=False, db_index=True)
     title = models.CharField(max_length=255)