• Use official 0.30 spec.txt.
• Add cmark_get_default_mem_allocator() (#330). API change: this
  adds a new exported function in cmark.h.
• Fix #383. An optimization we used for emphasis parsing was
  too aggressive, causing us to miss some emphasis that was legal
  according to the spec. We fix this by indexing the openers_bottom
  table not just by the type of delimiter and the length of the
  closing delimiter mod 3, but by whether the closing delimiter
  can also be an opener. (The algorithm for determining emphasis
  matching depends on all these factors.) Add regression test.
• Fix quadratic behavior with inline HTML (#299, Nick Wellnhofer).
  Repeated starting sequences like <?, <!DECL or <![CDATA[ could
  lead to quadratic behavior if no matching ending sequence was found.
  Separate the inline HTML scanners. Remember if scanning the whole input
  for a specific ending sequence failed and skip subsequent scans.
• Speed up hierarchy check in tree manipulation API (Nick Wellnhofer).
  Skip hierarchy check in the common case that the inserted child has
  no children.
• Fix quadratic behavior when parsing inlines (#373, Nick Wellnhofer).
  The inline parsing code would call cmark_node_append_child to append
  nodes. This public function has a sanity check which is linear in the
  depth of the tree. Repeated calls could show quadratic behavior in
  degenerate trees. Use a special function to append nodes without this
  check. (Issue found by OSS-Fuzz.)
• Replace invalid characters in XML output (#365, Nick wellnhofer).
  Control characters, U+FFFE and U+FFFF aren't allowed in XML 1.0, so
  replace them with U+FFFD (replacement character). This doesn't solve
  the problem how to roundtrip these characters, but at least we don't
  produce invalid XML.
• Avoid quadratic output growth with reference links (#354, Nick Wellnhofer).
  Keep track of the number bytes added through expansion of reference
  links and limit the total to the size of the input document. Always
  allow a minimum of 100KB. Unfortunately, cmark has no error handling,
  so all we can do is to stop expanding reference links without returning
  an error. This should never be an issue in practice though. The 100KB
  minimum alone should cover all real-world cases.
• Fix issue with type-7 HTML blocks interrupting paragraphs
  (see commonmark/commonmark.js#213).
• Treat textarea like script, style, pre (type 1 HTML block),
  in accordance with spec change.
• Define whitespace per spec (Asherah Conor).
• Add MAX_INDENT for xml (#355). Otherwise we can get quadratic
  increase in size with deeply nested structures.
• Fix handling of empty strings when creating XML/HTML output
  (Steffen Kieß).
• Commonmark renderer: always use fences for code (#317).
  This solves problems with adjacent code blocks being merged.
• Improve rendering of commonmark code spans with spaces (#316).
• Cleaner approach to max digits for numeric entities.
  This modifies unescaping in houdini_html_u.c rather than
  the entity handling in inlines.c. Unlike the other,
  this approach works also in e.g. link titles.
• Fix entity parser (and api test) to respect length limit on
  numeric entities.
• Don't allow link destinations with unbalanced unescaped parentheses.
  See commonmark/commonmark.js#177.
• print_usage(): Minor grammar fix, swap two words (#305, Øyvind A. Holm).
• Don't call memcpy with NULL as first parameter.
  This is illegal according to the C standard, sec. 7.1.4.
  See https://www.imperialviolet.org/2016/06/26/nonnull.html.
• Add needed include in blocks.c.
• Fix unnecessary variable assignment.
• Skip UTF-8 BOM if present at beginning of buffer (#334).
• Fix URL check in is_autolink (Nick Wellnhofer). In a recent commit,
  the check was changed to strcmp, but we really have to use strncmp.
• Fix null pointer deref in is_autolink (Nick Wellnhofer).
  Introduced by a recent commit. Found by OSS-Fuzz.
• Rearrange struct cmark_node (Nick Wellnhofer). Introduce multi-purpose
  data/len members in struct cmark_node. This is mainly used to store
  literal text for inlines, code and HTML blocks.
  Move the content strbuf for blocks from cmark_node to cmark_parser.
  When finalizing nodes that allow inlines (paragraphs and headings),
  detach the strbuf and store the block content in the node's data/len
  members. Free the block content after processing inlines.
  Reduces size of struct cmark_node by 8 bytes.
• Improve packing of struct cmark_list (Nick Wellnhofer).
• Use C string instead of chunk in a number of contexts (Nick Wellnhofer,
  #309). The node struct never references memory of other nodes now.
  Node accessors don't have to check for delayed creation of C strings,
  so parsing and iterating all literals using the public API should
  actually be faster than before. These changes also reduce the size
  of struct cmark_node.
• Add casts for MSVC10 (from kivikakk in cmark-cfm).
• commonmark renderer: better escaping in smart mode. When
  CMARK_OPT_SMART is enabled, we escape literal -, ., and quote
  characters when needed to avoid their being "smartified."
• Add options field to cmark_renderer.
• commonmark.c - use size_t instead of int.
• Include string.h in cmark-fuzz.c.
• Fix #220 (hash collisions for references) (Vicent Marti via cmark-gfm).
  Reimplemented reference storage as follows:
  1. New references are always inserted at the end of a linked list. This
     is an O(1) operation, and does not check whether an existing (duplicate)
     reference with the same label already exists in the document.
  2. Upon the first call to cmark_reference_lookup (when it is expected
     that no further references will be added to the reference map), the
     linked list of references is written into a fixed-size array.
  3. The fixed size array can then be efficiently sorted in-place in O(n
     log n). This operation only happens once. We perform this sort in a
     stable manner to ensure that the earliest link reference in the
     document always has preference, as the spec dictates. To accomplish
     this, every reference is tagged with a generation number when initially
     inserted in the linked list.
  4. The sorted array is then compacted in O(n). Since it was sorted in a
     stable way, the first reference for each label is preserved and the
     duplicates are removed, matching the spec.
  5. We can now simply perform a binary search for the current
     cmark_reference_lookup query in O(log n). Any further lookup calls
     will also be O(log n), since the sorted references table only needs to
     be generated once.
     The resulting implementation is notably simple (as it uses standard
     library builtins qsort and bsearch), whilst performing better than
     the fixed size hash table in documents that have a high number of
     references and never becoming pathological regardless of the input.
• Comment out unused function cmark_strbuf_cstr in buffer.h.
• Re-add --safe command-line option as a no-op (#344), for backwards
  compatibility.
• Update to Unicode 13.0
• Generate and install cmake-config file (Reinhold Gschweicher).
  Add full cmake support. The project can either be used with
  add_subdirectory or be installed into the system (or some other
  directory) and be found with find_package(cmark). In both cases the
  cmake target cmark::cmark and/or cmark::cmark_static is all that
  is needed to be linked. Previously the cmarkConfig.cmake file
  was generated, but not installed. As additional bonus of generation
  by cmake we get a generated cmake-config-version.cmake file for
  find_package() to search for the same major version.
  The generated config file is position independent, allowing the
  installed directory to be copied or moved and still work.
  The following four files are generated and installed:
  lib/cmake/cmark/cmark-config.cmake,
  lib/cmake/cmark/cmark-config-version.cmake,
  lib/cmake/cmark/cmark-targets.cmake,
  lib/cmake/cmark/cmark-targets-release.cmake.
• Adjust the MinGW paths for MinGW64 (Daniil Baturin).
• Fix CMake generator expression checking for MSVC (Nick Wellnhofer).
• Fix -Wconst-qual warning (Saleem Abdulrasool). This enables building
  with /Zc:strictString with MSVC as well.
• Improve and modernize cmake build (Saleem Abdulrasool).
  • Build: add exports targets for build tree usage (#307).
  • Uuse target properties for include paths.
  • Remove the unnecessary execute permission on CMakeLists.txt.
  • Reduce property computation in CMake.
  • Use CMAKE_INCLUDE_CURRENT_DIRECTORY.
  • Improve man page installation.
  • Only include GNUInstallDirs once.
  • Replace add_compile_definitions with add_compile_options
    since the former was introduced in 3.12 (#321).
  • Cleanup CMake (#319).
  • Inline a variable.
  • Use LINKER_LANGUAGE property for C++ runtime.
  • Use CMake to control C standard.
  • Use the correct variable.
  • Loosen the compiler check
  • Hoist shared flags to top-level CMakeLists
  • Remove duplicated flags.
  • Use add_compile_options rather than modify CMAKE_C_FLAGS.
  • Hoist sanitizer flags to global state.
  • Hoist -fvisibilty flags to top-level.
  • Hoist the debug flag handling.
  • Hoist the profile flag handling.
  • Remove incorrect variable handling.
  • Remove unused CMake includes.
• Remove "-rdynamic" flag for static builds (#300, Eric Pruitt).
• Fixed installation on other than Ubuntu GNU/Linux distributions
  (Vitaly Zaitsev).
• Link executable with static or shared library (Nick Wellnhofer).
  If CMARK_STATIC is on (default), link the executable with the static
  library. This produces exactly the same result as compiling the library
  sources again and linking with the object files.
  If CMARK_STATIC is off, link the executable with the shared library.
  This wasn't supported before and should be the preferred way to
  package cmark on Linux distros.
  Building only a shared library and a statically linked executable
  isn't supported anymore but this doesn't seem useful.
• Reintroduce version check for MSVC /TP flag (Nick Wellnhofer).
  The flag is only required for old MSVC versions.
• normalize.py: use html.escape instead of cgi.escape (#313).
• Fix pathological_tests.py on Windows (Nick Wellnhofer).
  When using multiprocessing on Windows, the main program must be
  guarded with a __name__ check.
• Remove useless __name__ check in test scripts (Nick Wellnhofer).
• Add CIFuzz (Leo Neat).
• cmark.1 - Document --unsafe instead of --safe (#332).
• cmark.1: remove docs for --normalize which no longer exists (#332).
• Add lint target to Makefile.
• Add uninstall target to Makefile.
• Update benchmarks (#338).
• Fix typo in documentation (Tim Gates).
• Increase timeout for pathological tests to avoid CI failure.
• Update the Racket wrapper with the safe -> unsafe flag change (Eli
  Barzilay).