Add migration to modify badly formatted tags

refs #5685, #5709

- cycle through all tags, removing leading commas and trim spaces
- if the string is empty, change to 'tag' - the slug base for this model
- if there is a change, save it

core/server/data/fixtures/index.js

@@ -239,6 +239,32 @@ to004 = function to004() {
         return Promise.resolve();
     });
     ops.push(upgradeOp);
+
+    // add ghost-frontend client if missing
+    upgradeOp = models.Tag.findAll(options).then(function (tags) {
+        var tagOps = [];
+        if (tags) {
+            tags.each(function (tag) {
+                var name = tag.get('name'),
+                    updated = name.replace(/^(,+)/, '').trim();
+
+                // If we've ended up with an empty string, default to just 'tag'
+                updated = updated === '' ? 'tag' : updated;
+
+                if (name !== updated) {
+                    tagOps.push(tag.save({name: updated}, options));
+                }
+            });
+            if (tagOps.length > 0) {
+                logInfo('Cleaning ' + tagOps.length + ' malformed tags');
+                return Promise.all(tagOps);
+            }
+        }
+        return Promise.resolve();
+    });
+
+    ops.push(upgradeOp);
+
     return Promise.all(ops);
 };