fix(save): fix save diff preview when path starts with ~/

gptme/tools/save.py

@@ -58,8 +58,10 @@ def execute_save(
 
     # TODO: add check that it doesn't try to write a file with placeholders!
 
-    if Path(fn).exists():
-        current = Path(fn).read_text()
+    path = Path(fn).expanduser()
+
+    if path.exists():
+        current = path.read_text()
         p = Patch(current, code)
         # TODO: if inefficient save, replace request with patch (and vice versa), or even append
         print_preview(p.diff_minimal(), "diff")
@@ -69,8 +71,6 @@ def execute_save(
         yield Message("system", "Save cancelled.")
         return
 
-    path = Path(fn).expanduser()
-
     # if the file exists, ask to overwrite
     if path.exists():
         if not confirm("File exists, overwrite?"):