Description:
Need to use xdirname instead of dirname when saving the file. Dirname will clobber the filename.

From the code:

```
/*
* dirname using strlcpy semantic.
* Like dirname() except an empty string is returned in
* place of "/". This means we can always add a trailing
* slash and be correct.
* Address portability issues by copying argument
* before using. Some implementations modify the input string.
*/
size_t
xdirname(char *dp, const char *path, size_t dplen)
```


Steps to reproduce:
Try to save any file


See my port here for the one line fix:
https://github.com/philipdexter/mg/blob/master/file.c#L674