Create diff-non-generated script.

Author: dmsnell

package.json

@@ -110,6 +110,7 @@
 		"build": "grunt build",
 		"build:dev": "grunt build --dev",
 		"dev": "grunt watch --dev",
+		"diff:non-generated": "sh ./tools/diff-non-generated.sh",
 		"test": "grunt test",
 		"watch": "grunt watch",
 		"grunt": "grunt",
@@ -139,4 +140,4 @@
 		"sync-gutenberg-packages": "grunt sync-gutenberg-packages",
 		"postsync-gutenberg-packages": "grunt wp-packages:sync-stable-blocks && grunt build --dev && grunt build"
 	}
-}
+}

tools/diff-non-generated.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env sh
+
+# Generate a list of all files not marked as auto-generated, and produce a
+# pathspec for the `git diff` command so it skips over them.
+#
+# Example:
+#
+#     ":!/src/wp-includes/assets/script-loader-packages.min.php" ":!/src/..."
+GENERATED=$(cat .gitattributes | grep "diff=generated" | cut -w -f1 | sed 's/^\(.*\)$/":!\1"/g' | paste -sd ' ' -)
+
+# This ENV cannot be passed directly afte the "--", so generate the command.
+CMD="git diff --exit-code -- $GENERATED"
+
+eval $CMD