feat: support devenv tasks (#447)

* feat: devenv tasks

* refactor: rework generator for overseer v2.0

---------

Co-authored-by: Steven Arcangeli <stevearc@stevearc.com>

Author: dmeijboom

lua/overseer/template/devenv.lua

@@ -0,0 +1,51 @@
+local overseer = require("overseer")
+
+---@param opts overseer.SearchParams
+---@return nil|string
+local function get_devenv_file(opts)
+  local devenv_nix = { "devenv.nix" }
+  return vim.fs.find(devenv_nix, { upward = true, type = "file", path = opts.dir })[1]
+end
+
+return {
+  cache_key = function(opts)
+    return get_devenv_file(opts)
+  end,
+  generator = function(opts, cb)
+    if vim.fn.executable("devenv") == 0 then
+      return 'Command "devenv" not found'
+    end
+    local devenv = get_devenv_file(opts)
+    if not devenv then
+      return "No devenv.nix file found"
+    end
+    local devenv_dir = vim.fs.dirname(devenv)
+    local ret = {}
+    overseer.builtin.system(
+      { "devenv", "shell", "echo $DEVENV_TASKS" },
+      { cwd = devenv_dir, text = true },
+      vim.schedule_wrap(function(out)
+        local ok, data = pcall(vim.json.decode, out.stdout, { luanil = { object = true } })
+
+        if not ok then
+          cb(data)
+          return
+        end
+
+        for _, task in ipairs(data) do
+          table.insert(ret, {
+            name = string.format("devenv %s", task.name),
+            builder = function()
+              return {
+                cwd = devenv_dir,
+                cmd = { "devenv", "tasks", "run", task.name },
+              }
+            end,
+          })
+        end
+
+        cb(ret)
+      end)
+    )
+  end,
+}