Update: Apple changed “Save As…” to the “expected” behaviour starting with OS X Mountain Lion 10.8.2. This post describes the “Save As…” behaviour in OS X Mountain Lion 10.8.0 and 10.8.1.
We have previously described about “Save As…” feature being back on OS X Mountain Lion. What we missed out is to highlight the caveat of using it.
Turns out that “Save As…” in OS X Mountain Lion is implemented slightly differently from what we have been used to. When you “Save As…” an editing document to a different file, all the changes you made will automatically be saved on the original document as well.
Let’s show “Save As…” in action. You retrieve a document “doc1.rtf” for editing using TextEdit. The document has one paragraph on it.
You start typing a new paragraph. Note that the window title bar now has the “Edited” status as shown in picture below.
Half way through typing, you realise it is better to keep this new changes in a different document. So you Option-click on the File menu and choose the “Save As…” option to save the changes as “doc2.rtf”.
After clicking on the “Save” button, you will now be working on the “doc2.rtf” file.
But, the original “edited” document “doc1.rtf” will now also be saved automatically with the changes you type in. That means “doc1.rtf” and “doc2.rtf” will have the same content. This is certainly not the intended behaviour you’d expected.
This appears not to be a bug as the same behaviour is found on OS X Mountain Lion 10.8.1 update. It is a system wide “feature” thus OS X Mountain Lion compatible document editing apps such as TextEdit, Pages, Pixelmator etc will incorporate the same “Save As…” behaviour.