[doc] Almost all .md docs parse with new cmark using lazylex.html.

Exception: doc/help-index.md, which needs to use ``` blocks.

build/doc.sh

@@ -328,8 +328,10 @@ all-help() {
   mkdir -p $TEXT_DIR
   rm -v -f $TEXT_DIR/*
 
-  help-index-html $HTML_DIR
-  log 'index text done'
+  if false; then
+    help-index-html $HTML_DIR
+    log 'help-index-html done'
+  fi
 
   split-and-render doc/help.md
 

doc/command-vs-expression-mode.md

@@ -114,16 +114,20 @@ Right I should have clarified – they don’t turn globbing back on. It’s jus
 
 It’s exactly like the difference between:
 
-    from glob import glob; glob('*.py')  # yes glob
-    os.listdir('*.py')  # no glob because it's not how listdir() works
+```python
+from glob import glob; glob('*.py')  # yes glob
+os.listdir('*.py')  # no glob because it's not how listdir() works
+```
 
 in Python. Single quoted strings in Oil are just like string literals in Python. Does that make sense?
 
 I’m not sure what you mean by myEcho? Both of these work in Oil just like they
 do in sh:
 
-    echo *
-    echo '*'
+```sh
+echo *
+echo '*'
+```
 
 Because you’ve never entered expression mode. You’re still in command mode.
 

lazylex/html.py

@@ -27,6 +27,15 @@ def log(msg, *args):
   print(msg, file=sys.stderr)
 
 
+class LexError(Exception):
+  def __init__(self, s, pos):
+    self.s = s
+    self.pos = pos
+
+  def __str__(self):
+    return '(LexError %r)' % (self.s[self.pos : self.pos + 20])
+
+
 class Output(object):
   """
   Takes an underlying input buffer and an output file.  Maintains a position in

lazylex/oil_doc.py

@@ -70,7 +70,7 @@ def ExpandLinks(s):
           out.SkipTo(href_end)
 
     elif tok_id == html.Invalid:
-      raise RuntimeError(s[start_pos : end_pos])
+      raise html.LexError(s, start_pos)
 
     start_pos = end_pos
 
@@ -217,7 +217,12 @@ def HighlightCode(s):
               code_lexer.PrintHighlighted(out)
 
               out.SkipTo(slash_code_left)
-            elif 1:
+
+            elif css_class == 'language-oil':
+              # TODO: Write an Oil syntax highlighter.
+              pass
+
+            else:
               # Here's we're REMOVING the original <pre><code>
               # Pygments gives you a <pre> already
 
@@ -241,7 +246,7 @@ def HighlightCode(s):
               f.write('<!-- done pygments -->\n')
 
     elif tok_id == html.Invalid:
-      raise RuntimeError(s[start_pos : end_pos])
+      raise html.LexError(s, start_pos)
 
     start_pos = end_pos