[clang-tools-extra] [llvm] [llvm] add support for mustache templating language (PR #105893)

[Nicolas van Kempen via llvm-commits]

https://github.com/nicovank commented:

Some comments.

Regarding usage of `std::string`: Right now the library takes a `StringRef` through `Template` and `Parser`, and then keeps (2-4?) copies of chunks of the input in `Token` (`RawBody` and `TokenBody`) then `ASTNode` (`RawBody` and `Body`). Does that sound correct and reasonable? IMO the ideal scenario is the input string is only owned by `Template` and the rest references that copy, but this is non-trivial if any manipulation is needed which might be the case here.

https://github.com/llvm/llvm-project/pull/105893