feat: Implement the github release helper with github.sh

lib/github.sh

@@ -0,0 +1,53 @@
+#!/usr/bin/env bash
+# GitHub API helper functions for Bootstrap installers
+
+# Usage: github_get_latest_release <owner/repo>
+# Prints the tag_name of the latest release.
+github_get_latest_release() {
+    local repo="$1"
+    local tag
+    tag=$(curl -fsSL "https://api.github.com/repos/$repo/releases/latest" | jq -r '.tag_name // empty')
+    echo "$tag"
+}
+
+# Usage: github_get_download_url <owner/repo> <tag> <regex_pattern>
+# Finds the asset matching the regex pattern in the specified release tag and prints its download URL.
+github_get_download_url() {
+    local repo="$1"
+    local tag="$2"
+    local pattern="$3"
+    
+    # If the tag is exactly 'latest', fetch the latest release asset list
+    local endpoint
+    if [ "$tag" = "latest" ]; then
+        endpoint="https://api.github.com/repos/$repo/releases/latest"
+    else
+        endpoint="https://api.github.com/repos/$repo/releases/tags/$tag"
+    fi
+    
+    local url
+    url=$(curl -fsSL "$endpoint" | jq -r --arg regex "$pattern" '.assets[] | select(.name | test($regex; "i")) | .browser_download_url' | head -n1)
+    echo "$url"
+}
+
+# Usage: github_download_asset <owner/repo> <tag> <regex_pattern> <dest_file>
+# Resolves the URL for the matching asset and downloads it to dest_file.
+github_download_asset() {
+    local repo="$1"
+    local tag="$2"
+    local pattern="$3"
+    local dest="$4"
+    
+    local url
+    url=$(github_get_download_url "$repo" "$tag" "$pattern")
+    
+    if [ -z "$url" ]; then
+        log_error "Could not find asset matching regex '$pattern' for $repo@$tag"
+        return 1
+    fi
+    
+    log_info "Downloading $url ..."
+    download_file "$url" "$dest"
+}
+
+export -f github_get_latest_release github_get_download_url github_download_asset