hadley/ggplot2 — pull request #325 by kohske (2011-12-25 02:26:04+00:00)
Title: aes_auto: wisely detect aes vars from data

here is a typical usege:

```
> df <- data.frame(x = 1, y = 1, col = 1, txt = 1)
> aes_auto(df)
List of 3
$ colour: symbol col
$ x : symbol x
$ y : symbol y
```

extra arguments are interpreted as manual aes-mapping (here, label = txt):

```
> aes_auto(df, label = txt)
List of 4
$ colour: symbol col
$ x : symbol x
$ y : symbol y
$ label : symbol txt
```