gmadl - garry's mod addon downloader
written in bash, released in public domain/CC0

                <!> important <!>
this script is designed for linux, but works under WSL if git cloned with
core.autocrlf set to input or false. (otherwise.. $'\r': command not found)

prerequisites: DepotDownloader, bash, curl, jq, wget
DepotDownloader: https://github.com/SteamRE/DepotDownloader/releases
most users will need the linux-x64 build. unzip in the same dir as gmadl.
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usage:
 - to download one or more addons:
    ./download-addon.sh 110871780 112806637 [...]
 - to download one or more collections:
    ./download-collection.sh 355803678 [...]
downloaded addons will be saved in addons/ in their respective folders
e.g. addons/110871780_1693877035669674771.

features:
 - downloads addons and collections with their respective scripts
 - saves metadata (json and human-readable) and images for addons
 - logs successfully downloaded addons to file
 - maybe more features to come? please give suggestions!

issues, notes and todos:
 - when fetching images, steam's servers may return a file with no
   filename or extension, causing wget to save the image as index.html.
   technically, this is something i can handle, but it's needlessly
   complicated to fix. (issue+todo)
 - download-collection.sh downloads *only* the addons within a collection,
   it does not download metadata for the collection itself. (todo)