Add cpplint description (#415)

* Add build/include_what_you_use to cpplint checks

* Fix all cpplint build/include_what_you_use issues

.github/CONTRIBUTING.md

@@ -18,6 +18,7 @@ In general, make sure the addition is well thought out and does not increase the
 * The test coverage is also measured, and that should remain 100%
 * Formatting should be done with pre-commit, otherwise the format check will not pass. However, it is trivial to apply this to your PR, so don't worry about this check. If you do want to run it, see below.
 * Everything must pass clang-tidy as well, run with `-DCLI11_CLANG_TIDY=ON` (if you set `-DCLI11_CLANG_TIDY_OPTIONS="-fix"`, make sure you use a single threaded build process, or just build one example target).
+* Your changes must also conform to most of the [Google C++ Style Guide](https://google.github.io/styleguide/cppguide.html) rules checked by [cpplint](https://github.com/cpplint/cpplint). For unused cpplint filters and justifications, see [CPPLINT.cfg](/CPPLINT.cfg).
 
 
 ## Pre-commit

CPPLINT.cfg

@@ -9,6 +9,6 @@ filter=-whitespace/blank_line  # Unnecessarily strict with blank lines that othe
 filter=-whitespace/parens,-whitespace/braces  # Conflict with clang-format
 
 # Filters to be included in future
-filter=-whitespace/indent,-whitespace/comments,-readability/braces,-build/include_what_you_use
+filter=-whitespace/indent,-whitespace/comments,-readability/braces
 filter=-legal/copyright  # Remove this line after Version 1.9
 

include/CLI/App.hpp

@@ -10,6 +10,7 @@
 #include <iterator>
 #include <memory>
 #include <numeric>
+#include <set>
 #include <sstream>
 #include <string>
 #include <utility>

include/CLI/Config.hpp

@@ -7,6 +7,8 @@
 #include <fstream>
 #include <iostream>
 #include <string>
+#include <utility>
+#include <vector>
 
 #include "CLI/App.hpp"
 #include "CLI/ConfigFwd.hpp"

include/CLI/ConfigFwd.hpp

@@ -7,6 +7,7 @@
 #include <fstream>
 #include <iostream>
 #include <string>
+#include <vector>
 
 #include "CLI/Error.hpp"
 #include "CLI/StringTools.hpp"

include/CLI/Error.hpp

@@ -7,6 +7,7 @@
 #include <stdexcept>
 #include <string>
 #include <utility>
+#include <vector>
 
 // CLI library includes
 #include "CLI/StringTools.hpp"

include/CLI/Formatter.hpp

@@ -3,7 +3,9 @@
 // Distributed under the 3-Clause BSD License.  See accompanying
 // file LICENSE or https://github.com/CLIUtils/CLI11 for details.
 
+#include <algorithm>
 #include <string>
+#include <vector>
 
 #include "CLI/App.hpp"
 #include "CLI/FormatterFwd.hpp"

include/CLI/FormatterFwd.hpp

@@ -6,6 +6,7 @@
 #include <map>
 #include <string>
 #include <utility>
+#include <vector>
 
 #include "CLI/StringTools.hpp"
 

include/CLI/Split.hpp

@@ -5,6 +5,7 @@
 
 #include <string>
 #include <tuple>
+#include <utility>
 #include <vector>
 
 #include "CLI/Error.hpp"

include/CLI/TypeTools.hpp

@@ -9,6 +9,7 @@
 #include <memory>
 #include <string>
 #include <type_traits>
+#include <utility>
 #include <vector>
 
 namespace CLI {

include/CLI/Validators.hpp

@@ -15,6 +15,8 @@
 #include <map>
 #include <memory>
 #include <string>
+#include <utility>
+#include <vector>
 
 // [CLI11:verbatim]