Check generated Jest snap file (#3874)

* Check generated Jest snap file

* Check file name rule first

ref: https://github.com/github/linguist/pull/3874/files#r146168309

* Check extension first

It must be cheaper
ref: https://github.com/github/linguist/pull/3874/files#r146168426

lib/linguist/generated.rb

@@ -62,6 +62,7 @@ module Linguist
       npm_shrinkwrap_or_package_lock? ||
       godeps? ||
       generated_by_zephir? ||
+      generated_jest_snap? ||
       minified_files? ||
       has_source_map? ||
       source_map? ||
@@ -525,5 +526,12 @@ module Linguist
       return false unless lines.count > 1
       return lines[0].start_with?("// Generated by the gRPC")
     end
+
+    # Internal: Is this a snap file of Jest?
+    #
+    # Return true or false
+    def generated_jest_snap?
+      name.end_with?(".snap") && name.include?("__snapshots__")
+    end
   end
 end

test/fixtures/Data/__snapshots__/Button.ios.js.snap

@@ -0,0 +1,31 @@
+exports[`test renders regular button 1`] = `
+<View
+  accessibilityComponentType={undefined}
+  accessibilityLabel={undefined}
+  accessibilityTraits={undefined}
+  accessible={true}
+  hitSlop={undefined}
+  onLayout={undefined}
+  onResponderGrant={[Function]}
+  onResponderMove={[Function]}
+  onResponderRelease={[Function]}
+  onResponderTerminate={[Function]}
+  onResponderTerminationRequest={[Function]}
+  onStartShouldSetResponder={[Function]}
+  style={
+    Object {
+      "borderRadius": 2,
+      "opacity": 1,
+    }
+  }
+  testID={undefined}>
+  <View
+    style={
+      Object {
+        "alignSelf": "center",
+        "zIndex": 999,
+      }
+    } />
+  Test
+</View>
+`;

test/test_generated.rb

@@ -115,5 +115,8 @@ class TestGenerated < Minitest::Test
 
     # PostScript
     generated_sample_loading_data("PostScript/lambda.pfa")
+
+    # Jest snap
+    generated_fixture_without_loading_data("Data/__snapshots__/Button.ios.js.snap")
   end
 end