Merge branch 'mauro' into docs-mw

Mauro says:

That's the final series to complete the migration of documentation
build: it converts get_feat from Perl to Python.

V2 is technically identical to v1: the only difference is that it
now uses tools/lib/python/feat to store the library logic.

With that, no Sphinx in-kernel extensions use fork anymore to call
ancillary scripts: everything is now importing Python methods
directly from the libraries.

There's nothing special on this conversion: it is a direct translation,
almost bug-compatible with the original version (*).

(*) I did solve two or three caveats on patch 1.

Most of the complexity of the script relies at the logic to produce
ReST tables. I do have here on my internal scripts a (somewhat) generic
formatter for ReST tables in Python. I was tempted to convert the logic
to use it, but, as this could cause regressions, I opted to not do it
right now, mainly because the matrix table logic is complex. Also,
I'm tempted to modify a little bit the output there, but extra tests
are required to see if PDF output would work with complex tables (I
remember I had a problem with that in the past). So, I'm postponing
such extra cleanup.

Author: Jonathan Corbet

Documentation/sphinx/kernel_feat.py

@@ -34,14 +34,18 @@
 import codecs
 import os
 import re
-import subprocess
 import sys
 
 from docutils import nodes, statemachine
 from docutils.statemachine import ViewList
 from docutils.parsers.rst import directives, Directive
 from sphinx.util.docutils import switch_source_input
 
+srctree = os.path.abspath(os.environ["srctree"])
+sys.path.insert(0, os.path.join(srctree, "tools/lib/python"))
+
+from feat.parse_features import ParseFeature                # pylint: disable=C0413
+
 def ErrorString(exc):  # Shamelessly stolen from docutils
     return f'{exc.__class__.__name}: {exc}'
 
@@ -84,18 +88,16 @@ def run(self):
 
         srctree = os.path.abspath(os.environ["srctree"])
 
-        args = [
-            os.path.join(srctree, 'tools/docs/get_feat.pl'),
-            'rest',
-            '--enable-fname',
-            '--dir',
-            os.path.join(srctree, 'Documentation', self.arguments[0]),
-        ]
+        feature_dir = os.path.join(srctree, 'Documentation', self.arguments[0])
 
-        if len(self.arguments) > 1:
-            args.extend(['--arch', self.arguments[1]])
+        feat = ParseFeature(feature_dir, False, True)
+        feat.parse()
 
-        lines = subprocess.check_output(args, cwd=os.path.dirname(doc.current_source)).decode('utf-8')
+        if len(self.arguments) > 1:
+            arch = self.arguments[1]
+            lines = feat.output_arch_table(arch)
+        else:
+            lines = feat.output_matrix()
 
         line_regex = re.compile(r"^\.\. FILE (\S+)$")