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Here is my test with Brigadier.
MyName-rmbp:brigadier-master MyName$ ./brigadier -h
Usage: brigadier [options]
Options:
-h, --help show this help message and exit
-m MODEL, --model=MODEL
System model identifier to use (otherwise this
machine's model is used). This can be specified
multiple times to download multiple models in a single
run.
-i, --install After the installer is downloaded, perform the install
automatically. Can be used on Windows only.
-o OUTPUT_DIR, --output-dir=OUTPUT_DIR
Base path where the installer files will be extracted
into a folder named after the product, ie.
'BootCamp-041-1234'. Uses the current directory if
this option is omitted.
-k, --keep-files Keep the files that were downloaded/extracted. Useful
only with the '--install' option on Windows.
-p PRODUCT_ID, --product-id=PRODUCT_ID
Specify an exact product ID to download (ie.
'031-0787'), currently useful only for cases where a
model has multiple BootCamp ESDs available and is not
downloading the desired version according to the post
date.
MyName-rMBP:brigadier-master MyName$ ./brigadier -m MacBook8,1 -o Bootcamp-MacBook8,1
Output directory Bootcamp-MacBook8,1 that was specified doesn't exist!
MyName-rMBP:brigadier-master MyName$ mkdir Bootcamp-MacBook8.1
MyName-rMBP:brigadier-master MyName$ ./brigadier -m MacBook8,1 -o Bootcamp-MacBook8.1
Using Mac model: MacBook8,1.
Model supported in package distribution file at http://swcdn.apple.com/content/downloads/28/26/031-24514/qx7ph7k6mewtcf4eyhxmiil gc7r2ikjgud/031-24514.English.dist.
Distribution 031-24514 supports the following models: MacBook8,1, MacBookAir5,1, MacBookAir5,2, MacBookAir6,1, MacBookAir6,2, MacBookAir7,1, MacBookAir7,2, MacBookPro9,1, MacBookPro9,2, MacBookPro11,1, MacBookPro11,2, MacBookPro11,3, MacBookPro11,4, MacBookPro11,5, MacBookPro12,1, MacPro6,1, Macmini6,1, Macmini6,2, Macmini7,1, iMac13,1, iMac13,2, iMac13,3, iMac14,1, iMac14,2, iMac14,3, iMac14,4, iMac15,1.
Making directory Bootcamp-MacBook8.1/BootCamp-031-24514..
Fetching Boot Camp product at URL http://swcdn.apple.com/content/downloads/28/26/031-24514/qx7ph7k6mewtcf4eyhxmiil gc7r2ikjgud/BootCampESD.pkg.
100.0% 1633591296 / 1633586781 bytes
Expanding flat package...
Extracting Payload...
Extracted to Bootcamp-MacBook8.1/BootCamp-031-24514/WindowsSupport.dmg.
Done.
MyName-rMBP:brigadier-master MyName$ cd Bootcamp-MacBook8.1/
MyName-rMBP:Bootcamp-MacBook8.1 MyName$ ls -lt
total 0
drwxr-xr-x 3 MyName staff 102 Aug 13 11:57 BootCamp-031-24514
MyName-rMBP:Bootcamp-MacBook8.1 MyName$ cd BootCamp-031-24514/
MyName-rMBP:BootCamp-031-24514 MyName$ ls -lt
total 3188544
-rw-r--r-- 1 MyName staff 1632530665 Aug 12 00:59 WindowsSupport.dmg
MyName-rMBP:BootCamp-031-24514 MyName$ pwd
/Users/MyName/Documents/brigadier-master/Bootcamp-MacBook8.1/BootCamp-031-24514
MyName-rMBP:BootCamp-031-24514 MyName$ ls
WindowsSupport.dmg
MyName-rMBP:BootCamp-031-24514 MyName$ openssl md5 WindowsSupport.dmg
MD5(WindowsSupport.dmg)= a3d3e4f4a950fe6b47c4cb55f7cd7e02