Worktree paths in git panel, take 2 (#26047)

Modified version of #25950. We still use worktree paths, but repo paths
with a status that lie outside the worktree are not excluded; instead,
we relativize them by adding `..`. This makes the list in the git panel
match what you'd get from running `git status` (with the repo's worktree
root as the working directory).

- [x] Implement + test new unrelativization logic
- [x] ~~When collecting repositories, dedup by .git abs path, so
worktrees can share a repo at the project level~~ dedup repos at the
repository selector layer, with repos coming from larger worktrees being
preferred
- [x] Open single-file worktree with diff when activating a path not in
the worktree

Release Notes:

- N/A

crates/outline_panel/src/outline_panel.rs

@@ -5169,7 +5169,7 @@ mod tests {
     use search::project_search::{self, perform_project_search};
     use serde_json::json;
     use util::path;
-    use workspace::OpenVisible;
+    use workspace::{OpenOptions, OpenVisible};
 
     use super::*;
 
@@ -5780,7 +5780,10 @@ mod tests {
             .update(cx, |workspace, window, cx| {
                 workspace.open_paths(
                     vec![PathBuf::from("/root/two")],
-                    OpenVisible::OnlyDirectories,
+                    OpenOptions {
+                        visible: Some(OpenVisible::OnlyDirectories),
+                        ..Default::default()
+                    },
                     None,
                     window,
                     cx,
@@ -5971,7 +5974,15 @@ struct OutlineEntryExcerpt {
 
         let _editor = workspace
             .update(cx, |workspace, window, cx| {
-                workspace.open_abs_path(PathBuf::from(path!("/root/src/lib.rs")), true, window, cx)
+                workspace.open_abs_path(
+                    PathBuf::from(path!("/root/src/lib.rs")),
+                    OpenOptions {
+                        visible: Some(OpenVisible::All),
+                        ..Default::default()
+                    },
+                    window,
+                    cx,
+                )
             })
             .unwrap()
             .await