feat(config): add git-aware directory session handling

lua/config/session.lua

@@ -0,0 +1,88 @@
+--- Git-aware directory sessions on top of resession's `dirsession` store.
+---
+--- Session identity is `<worktree root>@<ref>`, so every git worktree gets its
+--- own session (worktrees live in distinct directories) and every branch
+--- inside a worktree gets its own layout. Detached HEAD pins to the short
+--- commit; outside a repository the plain cwd is used, matching AstroNvim's
+--- default dirsession naming.
+---
+--- resession sanitizes `/` and `:` in session names, so slashes in worktree
+--- paths and branch names (`feat/foo`) are safe.
+--- @module config.session
+
+local M = {}
+
+local DIR = "dirsession"
+
+--- Run git in `cwd`; nil on failure or empty output.
+--- @param cwd string
+--- @param ... string git arguments
+--- @return string?
+local function git(cwd, ...)
+  local cmd = { "git", "-C", cwd }
+  for _, arg in ipairs { ... } do
+    cmd[#cmd + 1] = arg
+  end
+  local out = vim.trim(vim.fn.system(cmd))
+  if vim.v.shell_error ~= 0 or out == "" then return nil end
+  return out
+end
+
+--- Session name for the current working directory.
+--- @return string
+function M.name()
+  local cwd = vim.fn.getcwd()
+  local root = git(cwd, "rev-parse", "--show-toplevel")
+  if not root then return cwd end
+  -- `branch --show-current` is empty on detached HEAD; an unborn branch in a
+  -- fresh repo has no commit to fall back to.
+  local ref = git(cwd, "branch", "--show-current")
+    or git(cwd, "rev-parse", "--short", "HEAD")
+    or "HEAD"
+  return root .. "@" .. ref
+end
+
+--- Whether a saved session file exists for `name`.
+--- @param name string
+--- @return boolean
+function M.exists(name)
+  return vim.uv.fs_stat(require("resession.util").get_session_file(name, DIR)) ~= nil
+end
+
+--- Save the session for the current worktree/branch.
+--- @param opts? table extra resession save options
+function M.save(opts)
+  require("resession").save(M.name(), vim.tbl_extend("force", { dir = DIR }, opts or {}))
+end
+
+--- Load the session for the current worktree/branch.
+--- @param opts? table extra resession load options
+function M.load(opts)
+  require("resession").load(M.name(), vim.tbl_extend("force", { dir = DIR }, opts or {}))
+end
+
+--- Open the picker used when there is nothing to restore: git files inside a
+--- repository, plain file search outside one.
+local function pick_files()
+  local snacks = require "snacks"
+  local transform = require("config.ignore_patterns").create_picker_filter()
+  if snacks.git.get_root() then
+    snacks.picker.git_files { transform = transform }
+  else
+    snacks.picker.files { transform = transform }
+  end
+end
+
+--- VimEnter entry point: restore this worktree/branch session, or fall back to
+--- the file picker when none has been saved yet.
+function M.restore()
+  local name = M.name()
+  if M.exists(name) then
+    M.load { silence_errors = true }
+  else
+    -- defer so the picker opens after startup finished drawing the UI
+    vim.schedule(pick_files)
+  end
+end
+
+return M