make clear that we are currently only dealing with checkout during cl…

…one (#301)

git-worktree/src/index.rs

@@ -8,6 +8,9 @@ pub mod checkout {
     pub struct Options {
         /// capabilities of the file system
         pub fs: crate::fs::Context,
+        /// If true, we assume no file to exist in the target directory, and want exclusive access to it.
+        /// This should be enabled when cloning.
+        pub destination_is_initially_empty: bool,
     }
 
     quick_error! {
@@ -42,6 +45,9 @@ pub fn checkout<Find>(
 where
     Find: for<'a> FnMut(&oid, &'a mut Vec<u8>) -> Option<git_object::BlobRef<'a>>,
 {
+    if !options.destination_is_initially_empty {
+        todo!("non-clone logic isn't implemented or vetted yet");
+    }
     let root = path.as_ref();
     let mut buf = Vec::new();
     for (entry, entry_path) in index.entries_mut_with_paths() {
@@ -76,6 +82,7 @@ pub(crate) mod entry {
         root: &std::path::Path,
         index::checkout::Options {
             fs: crate::fs::Context { symlink, .. },
+            ..
         }: index::checkout::Options,
         buf: &mut Vec<u8>,
     ) -> Result<(), index::checkout::Error>

git-worktree/tests/index/mod.rs

@@ -9,32 +9,33 @@ mod checkout {
     use git_object::bstr::ByteSlice;
     use git_odb::FindExt;
     use git_worktree::index;
+    use git_worktree::index::checkout::Options;
     use tempfile::TempDir;
 
     use crate::fixture_path;
 
     #[test]
     fn allow_symlinks() -> crate::Result {
-        let opts = index::checkout::Options {
-            fs: git_worktree::fs::Context {
-                symlink: true,
-                ..Default::default()
-            },
-        };
+        let opts = opts_with_symlink(true);
         let (source_tree, destination) = setup_fixture_with_options(opts, "make_mixed_without_submodules")?;
 
         assert_equality(&source_tree, &destination, opts.fs.symlink)?;
         Ok(())
     }
 
-    #[test]
-    fn symlinks_become_files_if_disabled() -> crate::Result {
-        let opts = index::checkout::Options {
+    fn opts_with_symlink(symlink: bool) -> Options {
+        index::checkout::Options {
             fs: git_worktree::fs::Context {
-                symlink: false,
+                symlink,
                 ..Default::default()
             },
-        };
+            destination_is_initially_empty: true,
+        }
+    }
+
+    #[test]
+    fn symlinks_become_files_if_disabled() -> crate::Result {
+        let opts = opts_with_symlink(false);
         let (source_tree, destination) = setup_fixture_with_options(opts, "make_mixed_without_submodules")?;
 
         assert_equality(&source_tree, &destination, opts.fs.symlink)?;