From 32746249172760a6ce493ec78f12c360c3b2b7f6 Mon Sep 17 00:00:00 2001
From: "Kenneth G. Franqueiro" <kenneth.franqueiro@gmail.com>
Date: Mon, 5 May 2014 21:30:12 -0400
Subject: [PATCH] Add support for `clean` option

This adds support for a `clean` method/property, which receives a boolean
indicating whether to remove the destination directory before writing.
The default is `true` (consistent with previous behavior).

Setting this to `false` can allow for use in situations where the source
directory is a child of the destination directory, e.g. for gh-pages setups
where the source is contained within the same repository.  Note that
moved/removed files will need to be cleaned up by other means.
---
 Readme.md                                     |  4 +++
 bin/metalsmith                                |  6 ++--
 lib/index.js                                  | 26 +++++++++++++--
 test/fixtures/write-noclean/expected/empty.md |  0
 test/fixtures/write-noclean/expected/index.md |  1 +
 test/index.js                                 | 32 +++++++++++++++++++
 6 files changed, 63 insertions(+), 6 deletions(-)
 create mode 100644 test/fixtures/write-noclean/expected/empty.md
 create mode 100644 test/fixtures/write-noclean/expected/index.md

diff --git a/Readme.md b/Readme.md
index c2084e07..4660233c 100644
--- a/Readme.md
+++ b/Readme.md
@@ -139,6 +139,10 @@ Set the relative `path` to the source directory, or get the full one if no `path
 
 Set the relative `path` to the destination directory, or get the full one if no `path` is provided. The destination directory defaults to `./build`.
 
+#### #clean(boolean)
+
+Set whether to remove the destination directory before writing to it, or get the current setting. Defaults to `true`.
+
 #### #metadata(json)
 
 Get the global metadata. This is useful for plugins that want to set global-level metadata that can be applied to all files.
diff --git a/bin/metalsmith b/bin/metalsmith
index 593a5810..04d6a5ee 100755
--- a/bin/metalsmith
+++ b/bin/metalsmith
@@ -23,9 +23,9 @@ try {
  */
 
 var metalsmith = new Metalsmith(process.cwd());
-if (json.source) metalsmith.source(json.source);
-if (json.destination) metalsmith.destination(json.destination);
-if (json.metadata) metalsmith.metadata(json.metadata);
+['source', 'destination', 'metadata', 'clean'].forEach(function(key){
+  if (json[key]) metalsmith[key](json[key]);
+});
 
 /**
  * Plugins.
diff --git a/lib/index.js b/lib/index.js
index f9a22727..8cd3d57f 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -31,6 +31,7 @@ function Metalsmith(dir){
   this.data = {};
   this.source('src');
   this.destination('build');
+  this.clean(true);
 }
 
 /**
@@ -84,6 +85,17 @@ Metalsmith.prototype.destination = function(path){
   return this;
 };
 
+/**
+ * Get or set whether the destination directory will be removed before writing.
+ * @param  {Boolean} clean
+ * @return {Boolean or Metalsmith}
+ */
+Metalsmith.prototype.clean = function(clean){
+  if (!arguments.length) return this._clean;
+  this._clean = clean;
+  return this;
+};
+
 /**
  * Join path `strs` with the working directory.
  *
@@ -182,10 +194,18 @@ Metalsmith.prototype.read = function(fn){
 Metalsmith.prototype.write = function(files, fn){
   var dest = this.destination();
 
-  rm(dest, function(err){
-    if (err) return fn(err);
+  if (this.clean()) {
+    rm(dest, function(err){
+      if (err) return fn(err);
+      writeAll();
+    });
+  } else {
+    writeAll();
+  }
+
+  function writeAll(){
     each(Object.keys(files), write, fn);
-  });
+  }
 
   function write(file, done){
     var data = files[file];
diff --git a/test/fixtures/write-noclean/expected/empty.md b/test/fixtures/write-noclean/expected/empty.md
new file mode 100644
index 00000000..e69de29b
diff --git a/test/fixtures/write-noclean/expected/index.md b/test/fixtures/write-noclean/expected/index.md
new file mode 100644
index 00000000..fb4c35e7
--- /dev/null
+++ b/test/fixtures/write-noclean/expected/index.md
@@ -0,0 +1 @@
+body
\ No newline at end of file
diff --git a/test/index.js b/test/index.js
index 35728075..dff28bcc 100644
--- a/test/index.js
+++ b/test/index.js
@@ -35,6 +35,11 @@ describe('Metalsmith', function(){
     assert('build' == m._dest);
   });
 
+  it('should default clean to true', function(){
+    var m = Metalsmith('test/tmp');
+    assert(true === m._clean);
+  });
+
   describe('#use', function(){
     it('should add a plugin to the middleware stack', function(){
       var m = Metalsmith('test/tmp');
@@ -69,6 +74,19 @@ describe('Metalsmith', function(){
     });
   });
 
+  describe('#clean', function(){
+    it('should set the clean option', function(){
+      var m = Metalsmith('test/tmp');
+      m.clean(false);
+      assert(false === m._clean);
+    });
+
+    it('should get the value of the clean option', function(){
+      var m = Metalsmith('test/tmp');
+      assert(true === m.clean());
+    });
+  });
+
   describe('#metadata', function(){
     it('should get metadata', function(){
       var m = Metalsmith('test/tmp');
@@ -147,6 +165,20 @@ describe('Metalsmith', function(){
       });
     });
 
+    it('should not remove existing destination directory if clean is false', function(done){
+      var m = Metalsmith('test/fixtures/write-noclean');
+      m.clean(false);
+      exec('mkdir -p test/fixtures/write-noclean/build && touch test/fixtures/write-noclean/build/empty.md', function(err){
+        if (err) return done(err);
+        var files = { 'index.md': { contents: new Buffer('body') }};
+        m.write(files, function(err){
+          if (err) return done(err);
+          equal('test/fixtures/write-noclean/build', 'test/fixtures/write-noclean/expected');
+          done();
+        });
+      });
+    });
+
     it('should chmod an optional mode from file metadata', function(done){
       var m = Metalsmith('test/fixtures/write-mode');
       var files = {