The "extra" generators were created in CMake's early years to provide
support for users of specific IDEs by directly generating their project
files alongside make or ninja files. Nowadays the file-api provides a
more generic, maintainable, well-tested, and robust way for IDEs to view
CMake project build trees. Deprecate the legacy "extra" generators to
encourage the corresponding IDEs to use the file-api.
Fixes: #19090
More `.. versionadded` could be added later when the features,
variables and properties relevant to each generator are properly
documented.
Issue: #19715
Add variable `CMAKE_CODEBLOCKS_EXCLUDE_EXTERNAL_FILES` to optionally
exclude files from outside the project root from the project file
written by the CodeBlocks extra generator. This optionally restores
logic that had been removed by commit v2.8.3~40^2 (CodeBlocks Generator:
Do not omit files in the project file listing, 2010-10-05) in response
to QTCREATORBUG-2250.
Issue: #12110Fixes: #17188
Move "extra" generators to their own section instead of duplicating them
for each corresponding main generator. Divide the list of main
generators into command-line and IDE sections and sort the names within
each section. Document the environment from which each kind of
generator may be used.
Add a section to each "extra" generator documenting which main
generators may be used with it.
