This directory contains the hls-install project, an Haskell Language Server installer.
It is used when installing from sources.
Unlike other subdirectories (e.g. hls-graph or ghcide), this is not another package of the HLS project, but another project entirely (with another stack.yaml, another cabal.project, etc.). It just so happens to be in a subdirectory of HLS project for convenience, as this is tightly related to HLS.
The rationale behind this choice is to keep the installer completely isolated from main HLS code: different dependencies, different builds, etc.