[clang-tools-extra] [clang-doc] [feat] add --repository-line-prefix argument (PR #131280)

[Mohamed Emad via cfe-commits]

hulxv wrote:

Should I modify `HTMLGeneratorTest.cpp` to test `RepositoryLinePrefix`?
https://github.com/llvm/llvm-project/blob/7a370748c0928b9ccfe26127e54eb3c1a1827d75/clang-tools-extra/unittests/clang-doc/HTMLGeneratorTest.cpp#L179

https://github.com/llvm/llvm-project/pull/131280