[deploy] Could not determine git HEAD null

if you do:

```
mkdir test
cd test
jreleaser init
git init 
jreleaser deploy
```

you get this error:

```
Could not determine git HEAD
null
```

which I assume is failing as no commits. since when done a git commit it tells me:

```
Could not determine remote
repository doesn't have a remote named 'origin'
```