Update README with latest Usage

Add --skipnonexistent flag

README.md

@@ -24,7 +24,7 @@ You may need to add `~/bin` to your PATH variable if not already done. See [here
 
 # Usage
 ```help
-usage: vimtabdiff.py [-h] [--vim VIM] [--onlydiffs] pathA pathB
+usage: vimtabdiff.py [-h] [--vim VIM] [--onlydiffs] [--skipmissing] pathA pathB
 
 Show diff of files from two directories in vim tabs
 
@@ -33,9 +33,10 @@ positional arguments:
   pathB
 
 options:
-  -h, --help  show this help message and exit
-  --vim VIM   vim command to run
-  --onlydiffs  only open files where there is a diff
+  -h, --help     show this help message and exit
+  --vim VIM      vim command to run
+  --onlydiffs    only open files where there is a diff
+  --skipmissing  skip non-existent files
 ```
 
 ## Relevant vim tips

vimtabdiff.py

@@ -32,6 +32,9 @@ def parse_args() -> argparse.Namespace:
     parser.add_argument(
         "--onlydiffs", help="only open files where there is a diff", action="store_true"
     )
+    parser.add_argument(
+        "--skipmissing", help="skip non-existent files", action="store_true"
+    )
     return parser.parse_args()
 
 
@@ -87,9 +90,10 @@ def main() -> None:
             aPath = a.resolve() if a else os.devnull
             bPath = b.resolve() if b else os.devnull
             if (
-                args.onlydiffs
-                and a and b
-                and open(aPath, mode="rb").read() == open(bPath, mode="rb").read()
+                (args.skipmissing and (not a or not b)) or
+                (args.onlydiffs
+                    and a and b
+                    and open(aPath, mode="rb").read() == open(bPath, mode="rb").read())
             ):
                 continue
             print(f"tabedit {aPath} | vsp {bPath}", file=vimCmdFile)