add chinese for pages.cn/linux/add-apt-respository.md

pages.cn/common/cppclean.md

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+# cppclean
+
+> Find unused code in C++ projects.
+
+- Run in a project's folder:
+
+`cppclean {{path/to/project}}`
+
+- Run on a project where the headers are in the "inc1/" and "inc2/" folders:
+
+`cppclean {{path/to/project}} --include-path={{inc1}} --include-path={{inc2}}`
+
+- Run on a specific file "main.cpp":
+
+`cppclean {{main.cpp}}`
+
+- Run on the current directory, excluding the "build" directory:
+
+`cppclean {{.}} --exclude={{build}}`