Added the ability to limit the size of a collection

Readme.md

@@ -6,6 +6,7 @@ A [Metalsmith](https://github.com/segmentio/metalsmith) plugin that lets you gro
 
   - can match files by `collection` metadata
   - can match files by pattern
+  - can limit the number of files in a collection
   - adds collections to global metadata
   - adds `next` and `previous` references to each file in the collection
 
@@ -94,6 +95,19 @@ metalsmith.use(collections({
 }));
 ```
 
+On each collection definition, it's possible to add a `limit` option so that the
+collection length is not higher than the given limit:
+
+```js
+metalsmith.use(collections({
+  lastArticles: {
+    sortBy: 'date',
+    limit: 10
+  }
+}));
+```
+
+
 ## CLI Usage
 
 All of the same options apply, just add them to the `"plugins"` key in your `metalsmith.json` configuration:

lib/index.js

@@ -83,7 +83,7 @@ function plugin(opts){
     });
 
     /**
-     * Add `next` and `previous` references.
+     * Add `next` and `previous` references and apply the `limit` option
      */
 
     keys.forEach(function(key){
@@ -91,6 +91,10 @@ function plugin(opts){
       var settings = opts[key];
       var col = metadata[key];
       var last = col.length - 1;
+      if (opts[key].limit && opts[key].limit < col.length) {
+          col = metadata[key] = col.slice(0, opts[key].limit);
+          last = opts[key].limit - 1;
+      }
       if (settings.refer === false) return;
       col.forEach(function(file, i){
         if (0 != i) file.previous = col[i-1];

test/fixtures/limit/build/one.md

@@ -0,0 +1,2 @@
+
+one

test/fixtures/limit/build/three.md

@@ -0,0 +1,2 @@
+
+three

test/fixtures/limit/build/two.md

@@ -0,0 +1,2 @@
+
+two

test/fixtures/limit/src/one.md

@@ -0,0 +1,6 @@
+---
+collection: articles
+title: Alpha
+---
+
+one

test/fixtures/limit/src/three.md

@@ -0,0 +1,6 @@
+---
+collection: articles
+title: Gamma
+---
+
+three

test/fixtures/limit/src/two.md

@@ -0,0 +1,6 @@
+---
+collection: articles
+title: Beta
+---
+
+two

test/index.js

@@ -111,6 +111,46 @@ describe('metalsmith-collections', function(){
       });
   });
 
+  it('should accept a "limit" option', function (done){
+    var metalsmith = Metalsmith('test/fixtures/limit'),
+        limit = 2;
+    metalsmith
+      .use(collections({
+        articles: {
+            limit: limit,
+            sortBy: 'title',
+        }
+      }))
+      .build(function(err){
+        if (err) return done(err);
+        var articles = metalsmith.metadata().articles;
+        assert.equal(limit, articles.length);
+        assert.equal('Alpha', articles[0].title);
+        assert.equal('Beta', articles[1].title);
+        done();
+      });
+  });
+
+  it('should accept a "limit" higher than the collection length', function(done){
+    var metalsmith = Metalsmith('test/fixtures/limit');
+    metalsmith
+      .use(collections({
+        articles: {
+          sortBy: 'title',
+          limit: 25
+        }
+      }))
+      .build(function(err){
+        if (err) return done(err);
+        var articles = metalsmith.metadata().articles;
+        assert.equal(3, articles.length);
+        assert.equal('Alpha', articles[0].title);
+        assert.equal('Beta', articles[1].title);
+        assert.equal('Gamma', articles[2].title);
+        done();
+      });
+  });
+
   it('should add next and previous references', function(done){
     var metalsmith = Metalsmith('test/fixtures/references');
     metalsmith