scripts : add wc2wt.sh - create worktree from current HEAD (#22513)

* scripts : add wc2wt.sh - create worktree from current HEAD

Add a script to create a git worktree on a new branch from the current
HEAD. Similar to pr2wt.sh but for local development branches instead of
PRs.

Usage:
  ./scripts/wc2wt.sh gg/new-feature
  ./scripts/wc2wt.sh gg/new-feature "bash -l"

Assisted-by: llama.cpp:local pi

* cont : no need to try to delete the branch

scripts/wc2wt.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+
+# initialize a new worktree from a branch name:
+#
+# - creates a new branch from current HEAD
+# - creates a new worktree in a parent folder, suffixed with the branch name
+#
+# sample usage:
+#   ./scripts/wc2wt.sh gg/new-feature-foo-bar
+#   ./scripts/wc2wt.sh gg/new-feature-foo-bar opencode
+#   ./scripts/wc2wt.sh gg/new-feature-foo-bar "cmake -B build && cmake --build build"
+#   ./scripts/wc2wt.sh gg/new-feature-foo-bar "bash -l"
+
+function usage() {
+    echo "usage: $0 <branch_name> [cmd]"
+    exit 1
+}
+
+# check we are in the right directory
+if [[ ! -f "scripts/wc2wt.sh" ]]; then
+    echo "error: this script must be run from the root of the repository"
+    exit 1
+fi
+
+if [[ $# -lt 1 || $# -gt 2 ]]; then
+    usage
+fi
+
+BRANCH=$1
+
+if [[ -z "$BRANCH" ]]; then
+    echo "error: branch name must not be empty"
+    exit 1
+fi
+
+dir=$(basename $(pwd))
+# sanitize branch name for directory name (replace / with -)
+dir_suffix=$(echo "$BRANCH" | tr '/' '-')
+
+git worktree add -b "$BRANCH" "../$dir-$dir_suffix" HEAD
+
+og_path=$(pwd)
+wt_path=$(cd "../$dir-$dir_suffix" && pwd)
+
+echo "git worktree created in $wt_path"
+
+cd "$wt_path"
+
+# pi agent setup in the worktree
+if [[ -f "$og_path/.pi/SYSTEM.md" && ! -f ".pi/SYSTEM.md" ]]; then
+    mkdir -p .pi
+    ln -sfn "$og_path/.pi/SYSTEM.md" .pi/SYSTEM.md
+fi
+
+if [[ $# -eq 2 ]]; then
+    echo "executing: $2"
+    eval "$2"
+fi