add skill-installer skill

.github/skills/skill-installer/scripts/install-skill.sh

@@ -0,0 +1,145 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/../../../../" && pwd)"
+repo_skills_dir="$repo_root/.github/skills"
+global_skills_dir="${HOME}/.copilot/skills"
+
+source_input="${1:-}"
+scope_input="${2:-}"
+name_input="${3:-}"
+
+prompt() {
+  local message="$1"
+  local default_value="${2:-}"
+  local reply
+  if [[ -n "$default_value" ]]; then
+    read -r -p "${message} [${default_value}]: " reply
+    printf '%s\n' "${reply:-$default_value}"
+  else
+    read -r -p "${message}: " reply
+    printf '%s\n' "$reply"
+  fi
+}
+
+normalize_name() {
+  tr '[:upper:] ' '[:lower:]-' | tr -cd 'a-z0-9-'
+}
+
+rewrite_github_blob_url() {
+  local url="$1"
+  if [[ "$url" =~ ^https://github\.com/([^/]+)/([^/]+)/blob/([^/]+)/(.*)$ ]]; then
+    printf 'https://raw.githubusercontent.com/%s/%s/%s/%s\n' "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}" "${BASH_REMATCH[3]}" "${BASH_REMATCH[4]}"
+  else
+    printf '%s\n' "$url"
+  fi
+}
+
+extract_skill_name() {
+  local file="$1"
+  sed -n 's/^name:[[:space:]]*//p' "$file" | head -n 1
+}
+
+download_source() {
+  local url="$1"
+  local out="$2"
+  curl -fsSL "$url" -o "$out"
+}
+
+copy_skill_dir() {
+  local source_dir="$1"
+  local target_dir="$2"
+  local include_supporting_files="$3"
+
+  mkdir -p "$target_dir"
+  if [[ "$include_supporting_files" == "yes" ]]; then
+    cp -R "$source_dir"/. "$target_dir"/
+  else
+    cp "$source_dir/SKILL.md" "$target_dir/SKILL.md"
+  fi
+}
+
+if [[ -z "$source_input" ]]; then
+  source_input="$(prompt "Source path, directory, or GitHub SKILL.md URL")"
+fi
+
+if [[ -z "$scope_input" ]]; then
+  scope_input="$(prompt "Target scope (repo/global)" "repo")"
+fi
+
+if [[ "$scope_input" != "repo" && "$scope_input" != "global" ]]; then
+  printf 'Invalid scope: %s\n' "$scope_input" >&2
+  exit 1
+fi
+
+tmpdir="$(mktemp -d)"
+trap 'rm -rf "$tmpdir"' EXIT
+
+staging_dir="$tmpdir/staging"
+mkdir -p "$staging_dir"
+
+source_kind=""
+source_path="$source_input"
+
+if [[ "$source_input" =~ ^https?:// ]]; then
+  source_kind="url"
+  source_path="$(rewrite_github_blob_url "$source_input")"
+  download_source "$source_path" "$staging_dir/SKILL.md"
+elif [[ -d "$source_input" ]]; then
+  source_kind="directory"
+  skill_file="$source_input/SKILL.md"
+  if [[ ! -f "$skill_file" ]]; then
+    printf 'Missing SKILL.md in source directory: %s\n' "$source_input" >&2
+    exit 1
+  fi
+  include_supporting_files="$(prompt "Copy supporting files too? (yes/no)" "no")"
+  copy_skill_dir "$source_input" "$staging_dir" "$include_supporting_files"
+elif [[ -f "$source_input" ]]; then
+  source_kind="file"
+  cp "$source_input" "$staging_dir/SKILL.md"
+else
+  printf 'Source not found: %s\n' "$source_input" >&2
+  exit 1
+fi
+
+if [[ ! -f "$staging_dir/SKILL.md" ]]; then
+  printf 'No SKILL.md was staged from %s source.\n' "$source_kind" >&2
+  exit 1
+fi
+
+inferred_name="$(extract_skill_name "$staging_dir/SKILL.md")"
+if [[ -z "$name_input" ]]; then
+  name_input="$(prompt "Skill name" "${inferred_name:-skill}")"
+fi
+skill_name="$(printf '%s' "$name_input" | normalize_name)"
+
+if [[ -z "$skill_name" ]]; then
+  printf 'Skill name cannot be empty.\n' >&2
+  exit 1
+fi
+
+if [[ "$scope_input" == "repo" ]]; then
+  target_base="$repo_skills_dir"
+else
+  target_base="$global_skills_dir"
+fi
+
+target_dir="$target_base/$skill_name"
+if [[ -e "$target_dir" ]]; then
+  overwrite="$(prompt "Target exists at ${target_dir}. Overwrite? (yes/no)" "no")"
+  if [[ "$overwrite" != "yes" ]]; then
+    printf 'Aborted.\n'
+    exit 1
+  fi
+  rm -rf "$target_dir"
+fi
+
+mkdir -p "$target_dir"
+cp -R "$staging_dir"/. "$target_dir"/
+
+if [[ ! -f "$target_dir/SKILL.md" ]]; then
+  printf 'Install failed: %s/SKILL.md missing after copy.\n' "$target_dir" >&2
+  exit 1
+fi
+
+printf 'Installed %s skill to %s\n' "$skill_name" "$target_dir"