riji publish failed in some Operating systems which has case-sensitive filesystem (ex Linux)

riji publish is failed in my Linux server.  executing 'git diff head' is failed and it should be 'git diff HEAD', I think.

```
$ git diff head --name-only
fatal: ambiguous argument 'head': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'
```

```
$ git diff HEAD --name-only

```