feat: one store directory per checkout

src/commands/link/store.rs

@@ -109,7 +109,24 @@ fn git_root(ctx: &Ctx) -> Result<PathBuf> {
     )))?)
 }
 
+// the remote names the project and the checkout names its clone, so two clones
+// never share a directory
 fn repo_components(ctx: &Ctx, root: &Path) -> Result<PathBuf> {
+    Ok(project_components(ctx, root)?.join(checkout_name(root)))
+}
+
+// `<dir>-<hash>`: the directory for a human, the hash of the canonical path
+// for two checkouts in directories of one name
+fn checkout_name(root: &Path) -> String {
+    let hash = fingerprint(root.as_os_str().as_bytes());
+
+    match root.file_name() {
+        Some(dir) => format!("{}-{hash}", cleaned(&dir.to_string_lossy())),
+        None => hash,
+    }
+}
+
+fn project_components(ctx: &Ctx, root: &Path) -> Result<PathBuf> {
     if let Some(url) = git_origin_url(ctx) {
         if let Some(components) = components_from_remote(&url) {
             return Ok(components);
@@ -302,11 +319,13 @@ pub(super) fn leads(path: &Path, root: &Path) -> Leads {
 
 #[cfg(test)]
 mod tests {
-    use super::{components_from_remote, fingerprint, normalized, sanitize, sanitize_name};
+    use super::{
+        checkout_name, components_from_remote, fingerprint, normalized, sanitize, sanitize_name,
+    };
     use std::collections::HashSet;
     use std::ffi::OsStr;
     use std::os::unix::ffi::OsStrExt;
-    use std::path::PathBuf;
+    use std::path::{Path, PathBuf};
 
     #[test]
     fn parses_every_spelling_of_a_remote() {
@@ -407,6 +426,17 @@ mod tests {
         assert_eq!(sanitize_name(OsStr::new("afurnik")), "afurnik");
     }
 
+    #[test]
+    fn a_checkout_is_named_by_its_directory_and_its_path() {
+        let one = checkout_name(Path::new("/home/a/afurnik"));
+        let two = checkout_name(Path::new("/home/b/afurnik"));
+
+        assert!(one.starts_with("afurnik-"), "{one}");
+        assert_ne!(one, two);
+        // the root itself has no directory to be named after
+        assert_eq!(checkout_name(Path::new("/")), fingerprint(b"/"));
+    }
+
     #[test]
     fn a_store_root_is_absolute_with_the_dots_folded_out() {
         // it is written into every symlink add creates, and compared against the