clarify filename

gpx-rs/src/engine/state/history/global.rs

@@ -1,6 +1,6 @@
 use std::rc::Rc;
 
-use super::{Diff, Files, History, diff_between};
+use super::{Diff, Files, History, Renamer, diff_between};
 use crate::{CommandError, FileId};
 
 /// One history for the whole workspace: each entry is a state of all the files.
@@ -123,6 +123,22 @@ impl History for GlobalHistory {
             None => !self.entries.is_empty(),
         }
     }
+
+    fn rename(&mut self, id: FileId, name: &str) -> Option<Diff> {
+        let before = self.current()?.get(&id)?.clone();
+        let mut renamer = Renamer::new(name);
+        for entry in self.entries.iter_mut() {
+            if let Some(file) = entry.get(&id) {
+                let renamed = renamer.rename(file);
+                entry.insert(id, renamed);
+            }
+        }
+        let after = self.current()?.get(&id)?;
+        (!Rc::ptr_eq(&before, after)).then(|| Diff {
+            modified: vec![id],
+            ..Default::default()
+        })
+    }
 }
 
 #[cfg(test)]

gpx-rs/src/engine/state/history/mod.rs

@@ -57,6 +57,41 @@ pub trait History: Default + Debug {
 
     /// Whether [`History::redo`] would do something for these `files`.
     fn can_redo(&self, files: &[FileId]) -> bool;
+
+    /// Names a file `name` in all its states, as if it had always been called so: there is nothing
+    /// to undo. Says that the file changed, `None` if there is no such file or it is called so.
+    fn rename(&mut self, id: FileId, name: &str) -> Option<Diff>;
+}
+
+/// Names the states of a file: the ones that were shared stay shared (a state that several
+/// entries have is renamed once), and the ones that are called so already are kept.
+pub(super) struct Renamer<'a> {
+    name: &'a str,
+    renamed: HashMap<*const File, Rc<File>>,
+}
+
+impl<'a> Renamer<'a> {
+    pub(super) fn new(name: &'a str) -> Self {
+        Self {
+            name,
+            renamed: HashMap::new(),
+        }
+    }
+
+    pub(super) fn rename(&mut self, file: &Rc<File>) -> Rc<File> {
+        if file.info.name == self.name {
+            return file.clone();
+        }
+        let name = self.name;
+        self.renamed
+            .entry(Rc::as_ptr(file))
+            .or_insert_with(|| {
+                let mut renamed = (**file).clone();
+                renamed.info.name = name.to_owned();
+                Rc::new(renamed)
+            })
+            .clone()
+    }
 }
 
 /// Which files were added, removed or modified by a change of the current files.

gpx-rs/src/engine/state/history/per_file.rs

@@ -1,6 +1,6 @@
 use std::rc::Rc;
 
-use super::{Diff, Files, History, diff_between};
+use super::{Diff, Files, History, Renamer, diff_between};
 use crate::{CommandError, File, FileId};
 
 use std::collections::HashMap;
@@ -139,6 +139,20 @@ impl History for PerFileHistory {
         self.any(files, FileHistory::can_undo)
     }
 
+    fn rename(&mut self, id: FileId, name: &str) -> Option<Diff> {
+        let history = self.stacks.get_mut(&id)?;
+        let mut renamer = Renamer::new(name);
+        for entry in history.entries.iter_mut() {
+            *entry = renamer.rename(entry);
+        }
+        let current = history.current().clone();
+        let before = self.current.insert(id, current.clone());
+        (!before.is_some_and(|before| Rc::ptr_eq(&before, &current))).then(|| Diff {
+            modified: vec![id],
+            ..Default::default()
+        })
+    }
+
     fn can_redo(&self, files: &[FileId]) -> bool {
         self.any(files, FileHistory::can_redo)
     }