[clang-tools-extra] [clangd] Add support for textDocument/rangesFormatting (LSP 3.18) (PR #80180)

[Tom Praschan via cfe-commits]

tom-anders wrote:

Rebased to fixed merge conflict, extend lit test with test for new `rangesFormatting` request

@sam-mccall @HighCommander4 ping

https://github.com/llvm/llvm-project/pull/80180