check-variable-fonts.py: add a helper to display instructions

Use lib docstring to output the comments via --help/-h. With
that, update the default instructions to recomment it instead
of asking the user to read the source code.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Message-ID: <577162cf4e07de74c4a783f16e3404f0040e5e0a.1758196090.git.mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

tools/docs/check-variable-fonts.py

@@ -12,11 +12,21 @@ Detect problematic Noto CJK variable fonts.
 or more details, see lib/latex_fonts.py.
 """
 
+import argparse
 import sys
 
 from lib.latex_fonts import LatexFontChecker
 
-msg = LatexFontChecker().check()
+checker = LatexFontChecker()
+
+parser=argparse.ArgumentParser(description=checker.description(),
+                               formatter_class=argparse.RawTextHelpFormatter)
+parser.add_argument("--deny-vf",
+                    help="XDG_CONFIG_HOME dir containing fontconfig/fonts.conf file")
+
+args=parser.parse_args()
+
+msg = LatexFontChecker(args.deny_vf).check()
 if msg:
     print(msg)
 

tools/docs/lib/latex_fonts.py

@@ -105,14 +105,18 @@ class LatexFontChecker:
     translations.
     """
 
-    def __init__(self):
-        deny_vf = os.environ.get('FONTS_CONF_DENY_VF', "~/deny-vf")
+    def __init__(self, deny_vf=None):
+        if not deny_vf:
+            deny_vf = os.environ.get('FONTS_CONF_DENY_VF', "~/deny-vf")
 
         self.environ = os.environ.copy()
         self.environ['XDG_CONFIG_HOME'] = os.path.expanduser(deny_vf)
 
         self.re_cjk = re.compile(r"([^:]+):\s*Noto\s+(Sans|Sans Mono|Serif) CJK")
 
+    def description(self):
+        return __doc__
+
     def get_noto_cjk_vf_fonts(self):
         """Get Noto CJK fonts"""
 
@@ -154,8 +158,9 @@ class LatexFontChecker:
                 For CJK pages in PDF, they need to be hidden from XeTeX by denylisting.
                 Or, CJK pages can be skipped by uninstalling texlive-xecjk.
 
-                For more info on denylisting, other options, and variable font, see header
-                comments of {rel_file}.
+                For more info on denylisting, other options, and variable font, run:
+
+                    tools/docs/check-variable-fonts.py -h
             """)
         msg += "=" * 77