Tests were added. As I wrote the tests, I realized that GitRun was
printing to STDOUT even though we had created a local *STDOUT and opened
it to write to a memory file (like PageHtml does). Apparently this is
not inherited to the child process. I now use the solution provided for
in the perldoc for open. Unfortunately it requires a temp file. Trying
to use a memory file results in an error. Temporary files are a mess if
I want to access the output: I need to close it and reopen it for
reading. That's why GitRun only does that if $GitDebug is set. This is
what most of the tests will use: set $GitDebug and examine $GitResult.
At the same time I realized that the error message was never being
triggered. The previous code was tricky because it only considered
showing an error message in a non-void context, ie. when called from
maintenance. I wasn't sure this was an actual benefit and decided to
remove it altogether. I we really want to, we can set $GitDebug and
examine $GitResult in GitCleanup.
