feat: Add --reuse/-r flag to CLI for replacing workspace in existing window

[mateonoel2]

Closes #ISSUE

it is was still in discussion

Release Notes:

• Added: --reuse (-r) CLI flag to replace the workspace in an existing window instead of opening a new one

This PR adds a new --reuse (-r) CLI flag that allows users to replace the workspace in an existing Zed window instead of opening a new one or adding files to the current workspace.

What it does

The --reuse flag finds an available local workspace window and replaces its workspace with the newly specified paths. This provides a third workspace opening mode alongside the existing --add and --new flags.

Implementation Details

• CLI Flag: Added --reuse (-r) flag with proper mutual exclusion with --add and --new
• Window Replacement: Uses the existing replace_window option in workspace::OpenOptions
• Window Selection: Reuses the first available local workspace window
• Fallback Behavior: When no existing windows are found, creates a new window
• Test Coverage: Added comprehensive test for the reuse functionality

Behavior

• zed -r file.txt - Replaces the workspace in an available window with file.txt
• If no windows are open, creates a new window (same as default behavior)
• Mutually exclusive with -a/--add and -n/--new flags
• Works with multiple files and directories

Files Changed

• crates/cli/src/cli.rs - Added reuse field to CliRequest::Open
• crates/cli/src/main.rs - Added CLI argument definition and parsing
• crates/zed/src/zed/open_listener.rs - Implemented reuse logic and added tests
• crates/zed/src/zed/windows_only_instance.rs - Updated for Windows compatibility

Testing

• ✅ Unit tests pass
• ✅ Manual testing confirms expected behavior:
  • Works when no windows are open
  • Replaces workspace in existing window
  • Maintains compatibility with existing -a and -n flags
  • Proper help text display

Manual testing proof

In this first video we do a couple of tests:

• 1: What happens if we use the -r flag when there are no windows open?
  - works as expected. It opens the files in a new window.

• 2: Does it work as expected if there is already a window open. Does it overrides the workspace?
  - yes it does. When opening a different file it overrides the current window instead of creating a new one.

• 3: Does the -n flag still works as expected?
  - yes, it creates the project in a new window

• 4: What about the -a flag?
  - yes, on the last accessed page

• 5: we do the replace command. It overrides the first opened window, do we want this behavior?
  - It is good enough that it overrides one of the opened windows with the new project. It still makes the user automatically go to the window with the specified files

• 6: we use the -r command again replacing the workspace with a new one.
  - this indeed worked as expected

more_cli_testing.mp4

In here the we check how the --help flag now displays the new command. (Description was later updated)

comparing_cli_help.mp4