Ask git where its daemon is and use that

This changes the test helpers on Windows to use "git --exec-path"
(with whatever "git" GitPython is using) to find the directory that
contains "git-daemon.exe", instead of finding it in a PATH search.

Author: EliahKagan

README.md

@@ -121,9 +121,6 @@ _Important_: Right after cloning this repository, please be sure to have execute
 the `./init-tests-after-clone.sh` script in the repository root. Otherwise
 you will encounter test failures.
 
-On _Windows_, make sure you have `git-daemon` in your PATH. For MINGW-git, the `git-daemon.exe`
-exists in `Git\mingw64\libexec\git-core\`.
-
 #### Install test dependencies
 
 Ensure testing libraries are installed. This is taken care of already if you installed with:

test/lib/helper.py

@@ -182,7 +182,7 @@ def git_daemon_launched(base_path, ip, port):
             # and then CANNOT DIE!
             # So, invoke it as a single command.
             daemon_cmd = [
-                "git-daemon",
+                osp.join(Git()._call_process("--exec-path"), "git-daemon"),
                 "--enable=receive-pack",
                 "--listen=%s" % ip,
                 "--port=%s" % port,