feat: add worktree / workspaces implementation

Signed-off-by: kjuulh <contact@kjuulh.io>

README.md

@@ -37,4 +37,76 @@ With gitnow
 
 1. `git now`
 2. Enter parts of the project name and press enter
-3. Your project is automatically downloaded if it doesn't exist in an opinionated path dir, and move you there. 
+3. Your project is automatically downloaded if it doesn't exist in an opinionated path dir, and move you there.
+
+## Configuration
+
+Configuration lives at `~/.config/gitnow/gitnow.toml` (override with `$GITNOW_CONFIG`).
+
+### Custom clone command
+
+By default gitnow uses `git clone`. You can override this with any command using a [minijinja](https://docs.rs/minijinja) template:
+
+```toml
+[settings]
+# Use jj (Jujutsu) instead of git
+clone_command = "jj git clone {{ ssh_url }} {{ path }}"
+```
+
+Available template variables: `ssh_url`, `path`.
+
+### Worktrees
+
+gitnow supports git worktrees (or jj workspaces) via the `worktree` subcommand. This uses bare repositories so each branch gets its own directory as a sibling:
+
+```
+~/git/github.com/owner/repo/
+├── .bare/          # bare clone (git clone --bare)
+├── main/           # worktree for main branch
+├── feature-login/  # worktree for feature/login branch
+└── fix-typo/       # worktree for fix/typo branch
+```
+
+Usage:
+
+```bash
+# Interactive: pick repo, then pick branch
+gitnow worktree
+
+# Pre-filter repo
+gitnow worktree myproject
+
+# Specify branch directly
+gitnow worktree myproject -b feature/login
+
+# Print worktree path instead of entering a shell
+gitnow worktree myproject -b main --no-shell
+```
+
+All worktree commands are configurable via minijinja templates:
+
+```toml
+[settings.worktree]
+# Default: "git clone --bare {{ ssh_url }} {{ bare_path }}"
+clone_command = "git clone --bare {{ ssh_url }} {{ bare_path }}"
+
+# Default: "git -C {{ bare_path }} worktree add {{ worktree_path }} {{ branch }}"
+add_command = "git -C {{ bare_path }} worktree add {{ worktree_path }} {{ branch }}"
+
+# Default: "git -C {{ bare_path }} branch --format=%(refname:short)"
+list_branches_command = "git -C {{ bare_path }} branch --format=%(refname:short)"
+```
+
+For jj, you might use:
+
+```toml
+[settings]
+clone_command = "jj git clone {{ ssh_url }} {{ path }}"
+
+[settings.worktree]
+clone_command = "jj git clone {{ ssh_url }} {{ bare_path }}"
+add_command = "jj -R {{ bare_path }} workspace add --name {{ branch }} {{ worktree_path }}"
+list_branches_command = "jj -R {{ bare_path }} bookmark list -T 'name ++ \"\\n\"'"
+```
+
+Available template variables for worktree commands: `bare_path`, `worktree_path`, `branch`, `ssh_url`.