Find a certain string which was introduced in any commit on any branch.

Search through commits and find a certain string which was introduced in any commit on any branch

``` bash
$ git log -S'hello world' --source --all
```

Source: [http://stackoverflow.com/questions/5816134/git-finding-a-commit-that-introduced-a-string](http://stackoverflow.com/questions/5816134/git-finding-a-commit-that-introduced-a-string)
