feat(installer): add github_clone installer for repository-based tools

Clones or updates GitHub repositories to specified paths.
Used by ruby-build (rbenv plugin) and similar tools.

Features:
- Clone to custom path (with tilde expansion)
- Update existing clones (git fetch + reset)
- Track commits (before/after)
- Configurable branch
- Refresh snapshot after install

Author: CybotTM

scripts/installers/github_clone.sh

@@ -0,0 +1,90 @@
+#!/usr/bin/env bash
+# Generic installer for GitHub repository clones
+set -euo pipefail
+
+DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+. "$DIR/lib/install_strategy.sh"
+
+TOOL="${1:-}"
+if [ -z "$TOOL" ]; then
+  echo "Usage: $0 TOOL_NAME [ACTION]" >&2
+  exit 1
+fi
+
+ACTION="${2:-install}"
+
+CATALOG_FILE="$DIR/../catalog/$TOOL.json"
+if [ ! -f "$CATALOG_FILE" ]; then
+  echo "[$TOOL] Error: Catalog file not found: $CATALOG_FILE" >&2
+  exit 1
+fi
+
+# Parse catalog
+GITHUB_REPO="$(jq -r '.github_repo // ""' "$CATALOG_FILE")"
+CLONE_PATH="$(jq -r '.clone_path // ""' "$CATALOG_FILE")"
+BRANCH="$(jq -r '.branch // "master"' "$CATALOG_FILE")"
+
+if [ -z "$GITHUB_REPO" ]; then
+  echo "[$TOOL] Error: github_repo not specified in catalog" >&2
+  exit 1
+fi
+
+if [ -z "$CLONE_PATH" ]; then
+  echo "[$TOOL] Error: clone_path not specified in catalog" >&2
+  exit 1
+fi
+
+# Expand tilde in clone path
+CLONE_PATH="${CLONE_PATH/#\~/$HOME}"
+
+# Ensure git is available
+if ! command -v git >/dev/null 2>&1; then
+  echo "[$TOOL] Error: git not found. Please install git first." >&2
+  exit 1
+fi
+
+# Get current version/commit if already cloned
+before=""
+if [ -d "$CLONE_PATH/.git" ]; then
+  cd "$CLONE_PATH"
+  before="$(git rev-parse --short HEAD 2>/dev/null || echo "<unknown>")"
+  cd - >/dev/null
+fi
+
+# Clone or update
+if [ ! -d "$CLONE_PATH" ]; then
+  echo "[$TOOL] Cloning from https://github.com/$GITHUB_REPO" >&2
+  mkdir -p "$(dirname "$CLONE_PATH")"
+  git clone --depth=1 --branch="$BRANCH" "https://github.com/$GITHUB_REPO.git" "$CLONE_PATH" || {
+    echo "[$TOOL] Error: git clone failed" >&2
+    exit 1
+  }
+else
+  echo "[$TOOL] Updating repository at $CLONE_PATH" >&2
+  cd "$CLONE_PATH"
+  git fetch origin "$BRANCH" --depth=1 || {
+    echo "[$TOOL] Error: git fetch failed" >&2
+    exit 1
+  }
+  git reset --hard "origin/$BRANCH" || {
+    echo "[$TOOL] Error: git reset failed" >&2
+    exit 1
+  }
+  cd - >/dev/null
+fi
+
+# Get new version/commit
+after=""
+if [ -d "$CLONE_PATH/.git" ]; then
+  cd "$CLONE_PATH"
+  after="$(git rev-parse --short HEAD 2>/dev/null || echo "<unknown>")"
+  cd - >/dev/null
+fi
+
+# Report
+printf "[%s] before: %s\n" "$TOOL" "${before:-<none>}"
+printf "[%s] after:  %s\n" "$TOOL" "${after:-<unknown>}"
+printf "[%s] path:   %s\n" "$TOOL" "$CLONE_PATH"
+
+# Refresh snapshot after successful installation
+refresh_snapshot "$TOOL"