[vips] Make #remove chainable

Vips::Image#remove removes metadata from a Vips::Image, which can be
useful for reducing filesize of an image or stripping potentially
sensitive data.

Like Vips::Image#set, it isn't chainable by default because the method
doesn't return a Vips::Image instance. Like #set, this commit makes
`#remove` chainable as well.

CHANGELOG.md

@@ -1,3 +1,7 @@
+## HEAD
+
+* [vips] Make `#remove` that's used for removing image metadata chainable (@janko-m)
+
 ## 1.7.0 (2018-09-20)
 
 * [vips] `#rotate` now always calls `vips_similarity()` and forwards all options to it (@janko-m)

doc/vips.md

@@ -264,6 +264,7 @@ ImageProcessing::Vips
   .crop(0, 0, 300, 300)
   .invert
   .set("icc-profile-data", custom_profile)
+  .remove("xmp-data")
   .gaussblur(2)
   # ...
 ```

lib/image_processing/vips.rb

@@ -112,10 +112,11 @@ module ImageProcessing
         image.composite(overlay, mode, **options)
       end
 
-      # make Vips::Image#set, #set_type, and #set_value chainable
+      # make Vips::Image#set, #set_type, #set_value, and #move chainable
       def set(*args)       image.tap { |img| img.set(*args) }       end
       def set_type(*args)  image.tap { |img| img.set_type(*args) }  end
       def set_value(*args) image.tap { |img| img.set_value(*args) } end
+      def remove(*args)    image.tap { |img| img.remove(*args) }    end
 
       private
 

test/vips_test.rb

@@ -30,13 +30,18 @@ describe "ImageProcessing::Vips" do
     assert_similar expected, actual
   end
 
-  it "applies setting metadata" do
+  it "allows changing metadata" do
     image = ImageProcessing::Vips
       .copy
       .set("icc-profile-data", "foobar")
+      .set_type(Vips::BLOB_TYPE, "foo", "bar")
+      .remove("exif-data")
       .call(@portrait, save: false)
 
     assert_equal "foobar", image.get("icc-profile-data")
+    assert_equal "bar",    image.get("foo")
+
+    assert_raises(Vips::Error) { image.get("exif-data") }
   end
 
   it "applies format" do