This reverts commit f1e47e6554.
Since unfortunately it breaks the addition of the git commit hash
to the version string when building from the VisualStudio IDE.
I presume this happens because `git` is not of the "path" of the
build environment. The version string ends up "3.0~" only.
The old approach of reading .git/HEAD does not work when using git
worktrees, where the folder layout looks roughly like:
solvespace.git/ - bare clone (.git dir)
solvespace.git/work - example worktree containing master
solvespage.git/worktrees/work/ - .git dir of worktree
solvespage.git/worktrees/work/HEAD - actual HEAD ref for master
First attempt was to just get GIT_ROOT from `git rev-parse --git-dir` but
that wasn't enough, since:
1. GIT_ROOT points to solvespage.git/worktrees/work/
2. GIT_ROOT/HEAD points to refs/heads/master
3. GIT_ROOT/refs/heads/master does not exist but the old implementation
would want to use this to get the sha
so we need two invocations of git rev-parse
1. `git rev-parse --git-dir` to get GIT_DIR
needed for setting GIT_DEPENDS
2. `git rev-parse HEAD` to get the sha of the worktree's HEAD