Problem

git checkout <tree> -- <pathspec> fails with error: unable to unlink old '<path>': No such file or directory and exit code 255 when the target file is a virtual ProjFS projection that has not been materialized as a placeholder in a GVFS-mounted repo.

Files that have been accessed (and thus have a ProjFS placeholder with a physical NTFS entry) are unaffected — unlink() works fine for those. The failure is specific to files that exist only in the virtual projection: lstat() succeeds (ProjFS intercepts stat calls for projected files) but unlink() fails because there is no physical NTFS entry to delete.

Even without ProjFS, the unfixed code path is wasteful: it clears skip-worktree, writes the file to disk, and triggers ProjFS placeholder creation — all unnecessary because the virtual filesystem provider will serve the correct content once the index is updated.

Root Cause

update_some() in builtin/checkout.c creates a replacement cache entry with create_ce_flags(0) which unconditionally clears skip-worktree. This causes mark_ce_for_checkout_overlay() to mark the entry for checkout, and checkout_entry_ca() attempts unlink() + write_entry() on a path that may only exist as a virtual projection with no physical file.

Fix

Three changes in builtin/checkout.c, all gated on core_virtualfilesystem and/or ce_skip_worktree():

1. update_some(): Propagate CE_SKIP_WORKTREE from the existing index entry to the replacement entry when core_virtualfilesystem is set. The index is updated with the new tree entry's OID while the virtual filesystem flag is preserved.

2. mark_ce_for_checkout_overlay(): Allow skip-worktree entries that have CE_UPDATE (set by update_some for changed tree entries) to still match the pathspec, so report_path_error() does not reject them.

3. checkout_worktree(): Skip checkout_entry() for entries that have both CE_MATCHED and CE_SKIP_WORKTREE. The virtual filesystem provider will serve the correct content from the updated projection on next access.

Non-VFS repos and hydrated files (skip-worktree cleared by the VFS hook) are completely unaffected.

Related

Same approach as the CE_NEW_SKIP_WORKTREE propagation in #865 which avoids unnecessary lstats on virtualized paths during branch switches. Both bugs stem from skip-worktree being dropped on replacement cache entries, causing unnecessary physical filesystem operations on virtual files.

Tests

Two new tests in t/t1093-virtualfilesystem.sh:

1. checkout path preserves skip-worktree: Creates two commits with different file content, enables VFS mode with 0% hydration, removes the physical file, runs checkout HEAD~1 -- file, and verifies the index is updated while no file is written to disk.

2. restore --staged after checkout path: Verifies that restore --staged --ignore-skip-worktree-bits correctly restores the index entry back to HEAD after a checkout-path operation with skip-worktree preserved.

Verified that test 1 fails without the product code change (checkout writes the file to disk) and passes with it.

• This change only applies to the virtualization hook and VFS for Git.