gruntfile files named patterns, possible? - node.js

Question

I'm playing around with Ghost, and I'd like to make the gruntfile compile the sass files from my theme.
So I started by modifying the sass task:
...
sass: {
admin: {
files: {
'<%= paths.adminAssets %>/css/screen.css': '<%= paths.adminAssets %>/sass/screen.scss'
}
},
themes: {
files:{
'content/themes/**/css/ie.css': 'content/themes/**/src/sass/ie.sass',
'content/themes/**/css/print.css': 'content/themes/**/src/sass/print.sass',
'content/themes/**/css/screen.css': 'content/themes/**/src/sass/screen.sass'
}
}
}
...
I realised that I could simplfy this to :
...
sass: {
admin: {
files: {
'<%= paths.adminAssets %>/css/screen.css': '<%= paths.adminAssets %>/sass/screen.scss'
}
},
themes: {
files:{
'content/themes/**/css/*.css': 'content/themes/**/src/sass/*.sass',
}
}
}
...
But then I was thinking, why isn't it replacing the stars in the destination with what it matches from the source?
Ends up it was just creating the following:
$ ls -al ./content/themes/
total 0
drwxrwxr-x 1 zenobius zenobius 50 Nov 18 02:10 .
drwxrwxr-x 1 zenobius zenobius 46 Nov 15 11:02 ..
drwxrwxr-x 1 zenobius zenobius 6 Nov 18 02:10 ** <----- sigh
drwxrwxr-x 1 zenobius zenobius 128 Nov 15 11:02 casper
drwxrwxr-x 1 zenobius zenobius 250 Nov 18 00:08 crycilium
I guess my question is really:
can i use some kind of regex named patterns
could I use a function in the files option to process the output name as the destination?

Answer 1

So the solution was to make use of grunt.file.expandMapping, (thanks to : https://stackoverflow.com/a/16672303/454615):
...
themes: {
files: grunt.file.expandMapping([
"content/themes/**/src/**/*.sass",
"!content/themes/**/src/**/_*.sass",
], '', {
expand: true,
ext: '.css',
rename: function(base, src) {
grunt.log.write(base + " " + src);
return src.replace('/src/', '/../'); // or some variation
}
})
}
...