Attach adds a trusted folder to the current project without reopening it or moving its root. Attachments live in the primary project's private .openidea/workspace.json, and detaching the last one restores a plain project.
ProjectInfo.name stays the primary project's name; displayName supplies window titles, project tabs and Recent Projects. Attach is no longer a remembered opening policy, and File > Attach Project is available when the policy is not Ask. Attached folders must be trusted, and Restricted Mode names any attached folder that blocks trust. Explicit workspaces keep their behaviour and still cannot be created in or inside a linked project.
Adding projects to a workspace took one folder at a time. Choosing a folder that is not itself a project now scans below it, up to four levels and a shared entry budget, without following symlinks or descending into a project and skipping dependency, output and hidden directories. The projects found appear in a checklist with linked ones disabled; a folder with none is added as before. The scan is cancellable and runs in both the create and manage dialogs.
Fixes#2102
Project windows only joined a tab group when merged explicitly or restored at startup; the macOS "Prefer tabs when opening documents" setting was never read, so opening another project or a workspace always created a separate window.
New project windows now follow that preference: with Always they join the active project window's tab group (forming one if needed) and are selected; with In Full Screen they do so only while the active window is full screen; with Manually they stay separate. This covers every path that creates a project window — Open, recent projects, workspaces, drag and drop, and opening from the command line or Finder — while LightEdit windows and restored groups keep their behaviour. New Workspace now opens through the same Open project in policy as Open Workspace, and a race when toggling full screen during the join is fixed.
Fixes#678
Workspaces open several local project folders in one IDE session (File › New / Open / Manage Workspace…, or Attach when opening a project, which creates a workspace automatically for a plain project window). Member folders are the Project view roots and take part in indexing, Find in Files, Git, language servers, run configurations and builds; agent tasks choose which member they work in. Window › Merge All Project Windows groups project windows into one window with project tabs (switch, reorder, close, move to a new window), restored on reopen.
Closes#241Closes#198Closes#286
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