GetGitPath(): Fix path to git on MS-Windows.

[aforren1]

'where git' returns the path including 'git.exe', and GetGITInfo() only expects the path minus the executable. This chops the 'git.exe' off.

Successfully tested on Win11 + git from https://www.git-scm.com/. Originally, it would fail at the git describe step because the concatenated command was '"C:\Program Files\Git\cmd\git.exe"git'.

Unrelated, but any reason the Mac/Linux branch of GetGITInfo() couldn't be replaced with which git instead of checking predefined paths?

[kleinerm]

Thanks. Wrt. Mac/Linux. I don't know. Was written by the Brainard lab, and probably only tested on macOS at that time.
Possibly would just work, but would need testing. I guess this function is rarely used so far, certainly by myself, so bugs
can go undiscovered for long.