In order to install a Magento extension, the first step is usually to add the required files and folders to your current Magento installation. This can be a real pain on a Mac since its merge utility is rudimentary at best.
This is where rsync (which is available from the command line) comes in handy.
Common options
-a archive mode
-r recursive
-v verbose
Option 1
Merge all files and folders from source to destination (will overwrite files, not folders, in destination if source file exist with the same name under the same path)
rsync -arv SOURCE_DIR DEST_DIR
Option 2
Merge all files and folders from source to destination with the following rules:
- Do not overwrite files which already exist
- Skip destination files that are newer than the source
rsync -arvu SOURCE_DIR DEST_DIR --ignore-existing