add "show/hide hidden files" functions

modules/osx/README.md

@@ -36,6 +36,8 @@ Functions
   - `osx-rm-dir-metadata` deletes .DS\_Store, \_\_MACOSX cruft.
   - `osx-ls-download-history` displays the macOS download history.
   - `osx-rm-download-history` deletes the macOS download history.
+  - `showfiles` show hidden files in Finder.
+  - `hidefiles` hide hidden files from Finder.
 
 Authors
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modules/osx/functions/hidefiles

@@ -0,0 +1,3 @@
+# Hide hidden files from Finder.
+defaults write com.apple.finder AppleShowAllFiles NO
+killall Finder

modules/osx/functions/showfiles

@@ -0,0 +1,3 @@
+# Show hidden files in Finder.
+defaults write com.apple.finder AppleShowAllFiles YES
+killall Finder