feat(add): default start-point to source branch

Amolith created 

When using -b from inside a worktree without specifying a start-point,
defaults to the current worktree's branch.

Assisted-by: Claude Opus 4.5 via Amp

Change summary

src/wt/cmd/add.lua |  4 ++++
src/wt/git.lua     | 18 ++++++++++++++++++
2 files changed, 22 insertions(+)

Detailed changes

src/wt/cmd/add.lua 🔗 

@@ -70,6 +70,10 @@ function M.cmd_add(args)
 
 	local output, code
 	if create_branch then
+		-- Default start-point to source worktree's branch if inside one
+		if not start_point and source_worktree then
+			start_point = git.get_worktree_branch(git_dir, source_worktree)
+		end
 		-- Create new branch with worktree
 		if start_point then
 			output, code = shell.run_cmd(

src/wt/git.lua 🔗 

@@ -193,6 +193,24 @@ function M.parse_worktree_list(output)
 	return worktrees
 end
 
+---Get the branch checked out in a specific worktree
+---@param git_dir string
+---@param worktree_path string
+---@return string|nil branch name, or nil if detached/not found
+function M.get_worktree_branch(git_dir, worktree_path)
+	local output, code = run_cmd("GIT_DIR=" .. git_dir .. " git worktree list --porcelain")
+	if code ~= 0 then
+		return nil
+	end
+	local worktrees = M.parse_worktree_list(output)
+	for _, wt in ipairs(worktrees) do
+		if wt.path == worktree_path then
+			return wt.branch
+		end
+	end
+	return nil
+end
+
 ---Check if branch is checked out in any worktree
 ---@param git_dir string
 ---@param branch string