Merge pull request #2376 from staehle/user/jstaehle/fix-checkout-truncate-oss

bugfix: gix-worktree-state: Reduced-size files on checkout should be truncated to correct length

Author: Byron

gix-worktree-state/src/checkout/chunk.rs

@@ -224,10 +224,12 @@ where
                     inner: std::io::BufWriter::with_capacity(512 * 1024, file),
                     progress: bytes,
                 };
-                bytes_written += std::io::copy(&mut read, &mut write)?;
+                let actual_bytes = std::io::copy(&mut read, &mut write)?;
+                bytes_written += actual_bytes;
                 entry::finalize_entry(
                     delayed.entry,
                     write.inner.into_inner().map_err(std::io::IntoInnerError::into_error)?,
+                    actual_bytes,
                     set_executable_after_creation,
                 )?;
                 delayed_files += 1;

gix-worktree-state/src/checkout/entry.rs

@@ -135,7 +135,7 @@ where
             };
 
             // For possibly existing, overwritten files, we must change the file mode explicitly.
-            finalize_entry(entry, file, set_executable_after_creation)?;
+            finalize_entry(entry, file, num_bytes as u64, set_executable_after_creation)?;
             num_bytes
         }
         gix_index::entry::Mode::SYMLINK => {
@@ -276,19 +276,31 @@ pub(crate) fn open_file(
 }
 
 /// Close `file` and store its stats in `entry`, possibly setting `file` executable.
+///
+/// `desired_bytes` is the amount of bytes Git thinks the file should have after writing.
 pub(crate) fn finalize_entry(
     entry: &mut gix_index::Entry,
     file: std::fs::File,
+    desired_bytes: u64,
     #[cfg_attr(windows, allow(unused_variables))] set_executable_after_creation: bool,
 ) -> Result<(), crate::checkout::Error> {
     // For possibly existing, overwritten files, we must change the file mode explicitly.
     #[cfg(unix)]
     if set_executable_after_creation {
         set_executable(&file)?;
     }
+
+    let md = &gix_index::fs::Metadata::from_file(&file)?;
+    // A last sanity check: if the file wasn't truncated upon opening, which is good in case something
+    // goes wrong during writing, not everything is lost, then after writing the file is smaller than it was
+    // before, it needs truncation. We do that here.
+    let needs_truncation = md.len() > desired_bytes;
+    if needs_truncation {
+        file.set_len(desired_bytes)?;
+    }
     // NOTE: we don't call `file.sync_all()` here knowing that some filesystems don't handle this well.
     //       revisit this once there is a bug to fix.
-    entry.stat = Stat::from_fs(&gix_index::fs::Metadata::from_file(&file)?)?;
+    entry.stat = Stat::from_fs(md)?;
     file.close()?;
     Ok(())
 }

gix-worktree-state/tests/state/checkout.rs

@@ -710,3 +710,38 @@ fn setup_filter_pipeline(opts: &mut gix_filter::pipeline::Options) {
         required: true,
     }];
 }
+
+#[test]
+fn checkout_truncates_existing_longer_files() -> crate::Result {
+    let mut opts = opts_from_probe();
+    opts.overwrite_existing = false;
+    opts.destination_is_initially_empty = false;
+
+    // Use existing fixture and modify one file to be longer
+    let (_source_tree, destination, _index, _outcome) = checkout_index_in_tmp_dir_opts(
+        opts.clone(),
+        "make_mixed_without_submodules_and_symlinks",
+        None,
+        |_| true,
+        |dest| {
+            // Create a longer version of the "executable" file before checkout
+            let file_path = dest.join("executable");
+            std::fs::create_dir_all(dest)?;
+            std::fs::write(
+                &file_path,
+                b"This is much longer content that should be truncated to match git's version",
+            )?;
+            Ok(())
+        },
+    )?;
+
+    let file_path = destination.path().join("executable");
+    let final_content = std::fs::read(&file_path)?;
+    assert_eq!(
+        final_content[..].as_bstr(),
+        "content",
+        "File content should match git's version"
+    );
+
+    Ok(())
+}