In commit cbf6f82 in PR microsoft#349 the
ValidateGitCommand() helper function was refactored slightly to use
a new LinesShouldMatch() function; however, the inputs were
accidentally reversed, so here we correct the order of the "expected"
and "actual" string arguments passed to LinesShouldMatch().

On macOS and Linux platforms, we use rename(2) directly when
moving files with the SystemIORunner's MoveFile() method, instead
of using .NET Core's File.Move() method.  The latter actually
implements most file moves using a combination of link(2)
followed by unlink(2) on the source file.

The consequence of using link() instead of rename() is that on
recent versions of macOS, when running with Watchman, file
creation events may not be delivered by Watchman to Git when a
new hard link within the Git working tree is created if that
link points to an existing inode outside of the watched tree.
This in turn causes the MoveFileFromOutsideRepoToInsideRepoAndAdd()
test in GitCommandsTests to fail intermittently.

We can work around the problem by utilizing rename() directly, which
also parallels the behaviour of SystemIORunner's RenameDirectory()
method, added in commit 0a517fa.

See also:

facebook/watchman#858
https://github.com/dotnet/runtime/blob/94515f7bd34aabaab5ba6a1316f4a881cbf2370c/src/libraries/System.IO.FileSystem/src/System/IO/FileSystem.Unix.cs#L142-L144

We replicate for the Mac version of RunFunctionalTests.sh the
changes made in commit da2b813
for the Linux version, which permit manual runs of the functional
test suite after rebuilding the binaries by copying them into
the directory where the Scalar.FunctionalTests binary was published,
unless the --test-scalar-on-path option was given to the script.