Copying and modifying files

A relatively common task when building software is that some files must be copied to a specific location before the build. Most file operations can be done using the file() command at configuration time. For instance, copying files is done by invoking the following:

file(COPY_FILE old_file new_file)

There are several file operations available, such as file(REMOVE) and file(REMOVE_RECURSE) to delete files or directory trees, file(RENAME) to move files, and file(CHMOD) to change permissions on systems that support it. The full documentation of the file command is available here: https://cmake.org/cmake/help/latest/command/file.html.

But what if we want to copy and modify a file at the same time? In the Executing custom tasks at configuration time section, we saw an example where the git revision was retrieved and passed to the compiler as a preprocessor definition. A much nicer way to do this would be to generate a header file containing the necessary...