I don't know why, but the following commands do not work:
```
git fetch origin +refs/tags/phabricator/diff/*:refs/tags/phabricator/diff/*
git fetch origin +refs/tags/phabricator/*:refs/tags/phabricator/*
git fetch origin +refs/tags/*:refs/tags/*
```
While this works fine (note the lack of "diff/" on the local reference):
```
git fetch origin +refs/tags/phabricator/diff/*:refs/tags/phabricator/*
From git.pageuppeople.com:diffusion/PS
* [new tag] phabricator/diff/166823 -> phabricator/166823
* [new tag] phabricator/diff/166831 -> phabricator/166831
* [new tag] phabricator/diff/166833 -> phabricator/166833
* [new tag] phabricator/diff/166844 -> phabricator/166844
* [new tag] phabricator/diff/166875 -> phabricator/166875
* [new tag] phabricator/diff/166905 -> phabricator/166905
* [new tag] phabricator/diff/167668 -> phabricator/167668
* [new tag] phabricator/diff/167678 -> phabricator/167678
* [new tag] phabricator/diff/167715 -> phabricator/167715
* [new tag] phabricator/diff/167718 -> phabricator/167718
* [new tag] phabricator/diff/167754 -> phabricator/167754
* [new tag] phabricator/diff/167771 -> phabricator/167771
* [new tag] phabricator/diff/167782 -> phabricator/167782
* [new tag] phabricator/diff/167791 -> phabricator/167791
* [new tag] phabricator/diff/167793 -> phabricator/167793
* [new tag] phabricator/diff/167807 -> phabricator/167807
* [new tag] phabricator/diff/174130 -> phabricator/174130
* [new tag] phabricator/diff/174131 -> phabricator/174131
* [new tag] phabricator/diff/174132 -> phabricator/174132
* [new tag] phabricator/diff/174135 -> phabricator/174135
* [new tag] phabricator/diff/174136 -> phabricator/174136
* [new tag] phabricator/diff/174138 -> phabricator/174138
* [new tag] phabricator/diff/174142 -> phabricator/174142
* [new tag] phabricator/diff/174145 -> phabricator/174145
* [new tag] phabricator/diff/174147 -> phabricator/174147
* [new tag] phabricator/diff/174149 -> phabricator/174149
* [new tag] phabricator/diff/174151 -> phabricator/174151
* [new tag] phabricator/diff/174153 -> phabricator/174153
* [new tag] phabricator/diff/174156 -> phabricator/174156
* [new tag] phabricator/diff/174159 -> phabricator/174159
```
This causes issues when trying to fetch all diff tags into a cached version of a working copy, because there's no way to retrieve all of the diff tags with their original name.