This repository contains an embeddable utility script that could be used for fetching versions / releases / files / hash strings from various hosting services (GitHub, Docker Hub -- for now).

• automates fetching files / metadata from remote repositories;
• queryable metadata: version / tag + digest / hash, prefix/suffix matching, longest prefix ordering;
• download specific raw assets from a git repository (at requested / latest verison);
• supports GitHub files & releases, Docker Hub images, more to come (GitLab?)!;
• well documented & tested (hopefully)!

• bash, since the script is written in it!
• curl for fetching URLs;
• jq for JSON parsing.

You should install them using your distribution's package manager.

Download the script and put it in PATH or somewhere in your project's scripts directory (where you intend to make use of it):

wget -O fetch.sh "https://raw.githubusercontent.com/niflostancu/release-fetch-script/master/fetch.sh"
chmod +x fetch.sh

Excerpt from fetch.sh --help

Usage: `fetch.sh [OPTIONS] URL`
Fetches repository tag/asset/image version data and/or files.

The URL specifies the path to the repository & resource / asset to fetch.
You can specify custom service-specific filters inside the URI fragment (e.g., '#prefix=v2.')
You may also use a special '{VERSION}' placeholder in some of its components.
A service may have limited supported functions (e.g., no download / hash).

Options:
         --debug|-d: enable debug messages
         --version: prints the local fetch script's version string
         --latest: always fetch the latest version (overrides cache)
         --set-version=VERSION: fetch a specific version / commit string
         --set-*[=VALUE]: set configuration variables (alt. to fragment vars)
         --cache-file=FILE: file to cache the retrieved metadata vars
         --header|-H EXTRA_HEADER: specify extra headers to curl (for version fetching & download)
         --print-version: prints the version number (the default, if no other --print* present)
         --print-hash: prints the commit / asset's digest (multiple --print's are done in given order)
         --print-url: prints the download URL
         --download=DEST_NAME: uses curl to automatically download the asset to DEST_NAME
         --self-update: self updates this script (fetches the latest version and replaces self with it)

Fetch latest fzf release for linux_amd64:

fetch.sh --latest --download="fzf-{VERSION}.tar.gz" \
    "https://github.com/junegunn/fzf/releases/download/{VERSION}/fzf-{VERSION}-linux_amd64.tar.gz"

Retrieve the version & URL of Kubernetes' [nginx-controller] deployment script (on multiple lines, in the order given by the arguments):

# this project has prefixed releases as version string, e.g.: "controller-v1.8.2"
URL="https://raw.githubusercontent.com/kubernetes/ingress-nginx/{VERSION}/deploy/static/provider/cloud/deploy.yaml"
fetch.sh --print-version --print-url --set-prefix="controller-" "$URL"
# or:
fetch.sh --print-version --print-url "$URL#prefix=controller-"

Of course, you can add --download=<DEST_NAME> at any time you also wish to download the file! But you can also cache those in a separate file (this is useful when using fetch.sh for Makefile dependency management):

fetch.sh --cache-file=.cached.ver --print-hash "$URL#..."
cat .cached.ver
# e.g.: "controller-v1.8.2" + commit hash on second line

For DockerHub images, there is no download capability (you use the container deployment tool). But it's always useful to check whether a given base image has a new version:

fetch.sh --print-version --print-hash "https://hub.docker.com/_/alpine"

You can also use suffix and prefix and longest (to prefer the longest version string) specifiers! + Note: when the image has many tags, it is useful to also set a larger page_size parameter (max. number of entries returned by the request), otherwise the returned version may not be the last (the API doesn't guarantee results ordering):

fetch.sh --print-version "https://hub.docker.com/_/nextcloud#prefix=27.;suffix=-fpm-alpine;longest;page_size=200"