v2.7.0

This version adds a FileSize validator, a PositionalOnly prefix command
mode, and more control over config file generation. It also contains a large set
of bug fixes from a systematic audit of the parsing, config, help formatting,
string handling, and type conversion code, along with performance improvements
that remove unnecessary copies in hot paths.

Added

• Added a FileSize validator to check minimum and maximum file sizes.
  #1305
• Added PrefixCommandMode::PositionalOnly, which restores the pre-2.6.2 prefix
  command behavior as an opt-in mode: only a positional argument or the --
  separator triggers prefix mode, and unrecognized options are collected as
  extras. #1382
• Added an option to write only the active subcommand defaults when generating a
  config file. #1314

Changed

• Improved performance by removing unnecessary string and container copies in
  parsing and validator hot paths. #1368
• Improved the performance of string splitting by replacing a stringstream
  with a find-based loop. #1396
• Sorted the excludes and needs sets by name for stable help output.
  #1308
• Removed en_US.UTF-8 from the unicode locale fallback list. #1312
• Modernization and portability fixes: added missing standard includes, exported
  CLI::Number from the C++20 module, and cleaned up the warning lists.
  #1367
• Aligned the Meson build with wrapdb policy by removing disable_auto_if for
  subprojects. #1349

Fixed

• Fixed require_subcommand maximum enforcement for dot notation and for
  disabled fallthrough, dot-notation subcommands with Windows-style prefixes,
  get_options const/non-const consistency, and a crash when parsing with
  argc == 0. #1363, #1384
• Fixed missing symbol export from the precompiled shared library on macOS.
  #1387
• Fixed double indentation of nested option groups in help output. #1371,
  #1379
• Fixed config reading and writing bugs: section headers with trailing comments,
  one-line multiline comments, embedded delimiters with the Join policy, and
  multiline values for indented keys. #1369, #1361
• Fixed help formatting issues: hidden positionals appearing in the usage line,
  long subcommand names running into their descriptions, and ExtrasError
  reporting the wrong error name. #1369
• Fixed ignore_case and ignore_underscore so both apply when used together.
  #1358
• Fixed string handling edge cases in split_up, remove_quotes,
  append_codepoint, and escape_detect. #1364
• Fixed type conversion edge cases: negative input to unsigned types,
  whitespace-only floating point input, containers of pairs with an odd element
  count, large integer sums, and the Join policy with default values.
  #1362
• Fixed stale processed values being returned after Option::clear(). #1360
• Fixed out-of-bounds reads in the non-codecvt narrow/widen conversion paths
  used under C++26. #1359
• Fixed infinite recursion on subcommand option groups with fallthrough enabled.
  #1316
• Fixed empty strings given to wrapper types such as std::optional to
  consistently produce a default-constructed value. #1340
• Fixed CLI::ExistingFile to reject an empty filename with a clear error.
  #1351
• Fixed an empty description on a modified Transformer. #1345
• Fixed unsigned wraparound in split_program_name for command lines without
  spaces. #1339
• Fixed FileOnDefaultPath with an empty default path, and PositiveNumber
  rejecting subnormal values. #1366
• Fixed compilation with libc++/clang in C++26 mode. #1326
• Fixed the case of the shell32 library name in CMake. #1347
• Removed the static keyword from the precompiled library definition in CMake.
  #1304

Documentation

• Clarified the behavior of the prefix_command overloads. #1310
• Documented the Catch2 dependency for the test build. #1342
• Corrected documentation errors, including the AsSizeValue example, the
  App::required() doc, and validator comments. #1304, #1366
• Modernized some documentation. #1336
• Moved the tutorial book into the Doxygen documentation, modernized the HTML
  output with doxygen-awesome-css, and reorganized the sidebar navigation.
  #1390, #1392, #1397, #1398
• Corrected errors found in a documentation review. #1394
• Split the documentation into Guide and Examples sections and filled gaps in
  the guide. #1400

Internal

• Added a dev CMake preset and workflow for faster local iteration using the
  precompiled library and ccache. #1387
• Added a CUDA test for the single-header build. #1381
• Refactored the duplicated parse-completion pipeline and removed dead code.
  #1365
• Moved static std::string reference initializers to helper functions.
  #1335
• Routed formatter label fallback through an internal helper as a step toward
  internationalization support. #1320
• Cleaned up the CMake logic for finding Catch2 and Boost, and corrected the
  example test regular expressions. #1325, #1322
• Reorganized the GitHub workflows and reduced CI build times. #1323,
  #1387
• Added C++26 CI coverage (GCC, and clang with modules), and made codecov wait
  for all coverage uploads. #1388, #1391
• Tidied the configuration files in the root directory. #1393
• Attached the source packages to tagged releases, wrote the release notes from
  the changelog, and added a CI check for a changelog entry on every build.
  #1401, #1402, #1403