Added support for non-symlink checkouts on Windows when elevated righ…

…ts are missing

This implementation mimicks the behavior of Git on Windows
Signed-off-by: Felix Kollmann <[email protected]>

worktree.go

@@ -554,6 +554,22 @@ func (w *Worktree) checkoutFileSymlink(f *object.File) (err error) {
 	}
 
 	err = w.Filesystem.Symlink(string(bytes), f.Name)
+
+	// On windows, this might fail.
+	// Follow Git on Windows behavior by writing the link as it is.
+	if err != nil && isSymlinkWindowsNonAdmin(err) {
+		mode, _ := f.Mode.ToOSFileMode()
+
+		to, err := w.Filesystem.OpenFile(f.Name, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, mode.Perm())
+		if err != nil {
+			return err
+		}
+
+		defer ioutil.CheckClose(to, &err)
+
+		_, err = to.Write(bytes)
+		return err
+	}
 	return
 }
 

worktree_darwin.go

@@ -20,3 +20,7 @@ func init() {
 		}
 	}
 }
+
+func isSymlinkWindowsNonAdmin(err error) bool {
+	return false
+}

worktree_linux.go

@@ -20,3 +20,7 @@ func init() {
 		}
 	}
 }
+
+func isSymlinkWindowsNonAdmin(err error) bool {
+	return false
+}

worktree_windows.go

@@ -3,6 +3,7 @@
 package git
 
 import (
+	"os"
 	"syscall"
 	"time"
 
@@ -18,3 +19,17 @@ func init() {
 		}
 	}
 }
+
+func isSymlinkWindowsNonAdmin(err error) bool {
+	const ERROR_PRIVILEGE_NOT_HELD syscall.Errno = 1314
+
+	if err != nil {
+		if errLink, ok := err.(*os.LinkError); ok {
+			if errNo, ok := errLink.Err.(syscall.Errno); ok {
+				return errNo == ERROR_PRIVILEGE_NOT_HELD
+			}
+		}
+	}
+
+	return false
+}