New option --single-letters for shell.py

README.md

@@ -683,7 +683,8 @@ They can be suppressed with `python3 shell.py ... 2>/dev/null`.
 python3 shell.py [--html] [--link] [--include] [--extract macros]
                  [--language lang] [--t2t-lang lang] [--encoding ienc]
                  [--replace file] [--define file] [--disable rules]
-                 [--context number] [--skip regex] [--plain] [--server]
+                 [--context number] [--skip regex]
+                 [--single-letters accept] [--plain] [--server]
                  latex_file [latex_file ...] [> text_or_html_file]
 ```
 Option names may be abbreviated.
@@ -715,6 +716,13 @@ Default option values are set at the Python script beginning.
 - option `--context number`:<br>
   number of context lines displayed around each marked text region
   in HTML report; default: 2; negative number: display whole text
+- option `--single-letters accept`:<br>
+  check for single letters, accepting those in the patterns given as list
+  separated by '\|';
+  for instance `--singe-letters 'A|a|I|e.g.|i.e.'` for an English text
+  without equations;
+  all characters except '\|' are taken verbatim, but '~' and '\\,' are
+  interpreted as UTF-8 non-breaking space and narrow non-breaking space
 - option `--plain`:<br>
   assume plain-text input: no evaluation of LaTeX syntax;
   cannot be used together with option --include or --replace