Added a downgrading guide doc

downgrading.md

@@ -0,0 +1,30 @@
+## Automatically using `ipfs-update`
+
+TODO
+
+## Manually downgrading IPFS versions
+
+Downgrading your IPFS version (for instance, from `0.4.0` to `0.3.8`) is not as complicated as upgrading. You can't use the same repository simultaneously for both versions. Here is how you switch
+
+First, go to your repo for IPFS, check out the right branch, and re-install.
+
+```sh
+cd $GOPATH/src/github.com/ipfs/go-ipfs
+git checkout master # (or the version you want)
+go install ./cmd/ipfs
+```
+
+Then to backup your repo:
+
+```sh
+mv ~/.ipfs ~/.ipfs.bak
+```
+
+Finally, run:
+
+```sh
+ipfs init
+ipfs daemon
+```
+
+And you should be all set.