Squashed 'libs/CommService/' content from commit 7ccc0fc

git-subtree-dir: libs/CommService
git-subtree-split: 7ccc0fce88bbc5969df060058cf0fb57abe3bcf9

libs/CLI11/book/README.md

@@ -0,0 +1,94 @@
+# CLI11: An introduction
+
+This gitbook is designed to provide an introduction to using the CLI11 library
+to write your own command line programs. The library is designed to be clean,
+intuitive, but powerful. There are no requirements beyond C++11 support (and
+even `<regex>` support not required). It works on Mac, Linux, and Windows, and
+has 100% test coverage on all three systems. You can simply drop in a single
+header file (`CLI11.hpp` available in [releases][]) to use CLI11 in your own
+application. Other ways to integrate it into a build system are listed in the
+[README][].
+
+The library was inspired the Python libraries [Plumbum][] and [Click][], and
+incorporates many of their user friendly features. The library is extensively
+documented, with a [friendly introduction][readme], this tutorial book, and more
+technical [API docs][].
+
+> Feel free to contribute to [this documentation here][cli11tutorial] if
+> something can be improved!
+
+The syntax is simple and scales from a basic application to a massive physics
+analysis with multiple models and many parameters and switches. For example,
+this is a simple program that has an optional parameter that defaults to 0:
+
+```term
+gitbook $ ./a.out
+Parameter value: 0
+
+gitbook $ ./a.out -p 4
+Parameter value: 4
+
+gitbook $ ./a.out --help
+App description
+Usage: ./a.out [OPTIONS]
+
+Options:
+  -h,--help                   Print this help message and exit
+  -p INT                      Parameter
+```
+
+Like any good command line application, help is provided. This program can be
+implemented in 10 lines:
+
+[include](code/intro.cpp)
+
+[Source code](https://github.com/CLIUtils/CLI11/blob/main/book/code/intro.cpp)
+
+Unlike some other libraries, this is enough to exit correctly and cleanly if
+help is requested or if incorrect arguments are passed. You can try this example
+out for yourself. To compile with GCC:
+
+```term
+gitbook:examples $ c++ -std=c++11 intro.cpp
+```
+
+Much more complicated options are handled elegantly:
+
+```cpp
+std::string file;
+app.add_option("-f,--file", file, "Require an existing file")
+  ->required()
+  ->check(CLI::ExistingFile);
+```
+
+You can use any valid type; the above example could have used a
+`boost::file_system` file instead of a `std::string`. The value is a real value
+and does not require any special lookups to access. You do not have to risk
+typos by repeating the values after parsing like some libraries require. The
+library also handles positional arguments, flags, fixed or unlimited repeating
+options, interdependent options, flags, custom validators, help groups, and
+more.
+
+You can use subcommands, as well. Subcommands support callback lambda functions
+when parsed, or they can be checked later. You can infinitely nest subcommands,
+and each is a full `App` instance, supporting everything listed above.
+
+Reading/producing `.ini` files for configuration is also supported, as is using
+environment variables as input. The base `App` can be subclassed and customized
+for use in a toolkit (like [GooFit][]). All the standard shell idioms, like
+`--`, work as well.
+
+CLI11 was developed at the [University of Cincinnati][] in support of the
+[GooFit][] library under [NSF Award 1414736][nsf 1414736]. It was featured in a
+[DIANA/HEP][] meeting at CERN. Please give it a try! Feedback is always welcome.
+
+[goofit]: https://github.com/GooFit/GooFit
+[diana/hep]: https://diana-hep.org
+[cli11tutorial]: https://cliutils.github.io/CLI11/book
+[releases]: https://github.com/CLIUtils/CLI11/releases
+[api docs]: https://cliutils.github.io/CLI11
+[readme]: https://github.com/CLIUtils/CLI11/blob/main/README.md
+[nsf 1414736]: https://nsf.gov/awardsearch/showAward?AWD_ID=1414736
+[university of cincinnati]: https://www.uc.edu
+[plumbum]: https://plumbum.readthedocs.io/en/latest/
+[click]: https://click.palletsprojects.com