Document details of -g flag arguments

ghcup has a wonderful capability to compile HLS from sources, giving specific commit or reference, via flag -g ....

The problem is - it does not explain, nor offers any examples how to specify a commit, beyond mentioning version like -v 1.4.0, or master itself like -g master.

$ ghcup compile hls --help
. . . . .
  -g,--git-ref GIT_REFERENCE
                           The git commit/branch/ref to build from
. . . . .

It would be great if there were a few examples for commit/branch/ref.

Also, there's a confusing message:

[ Info  ] Git version master corresponds to HLS version 1.7.0.0
[ Info  ] Building HLS 1.7.0.0 for GHC version <whatever GHC was specified>

The master definitely is not v1.7.0.0. So, does the above mean that instead of building master, it rebuilds 1.7.0.0 from the source?