Always capture output for GitCommand

Switch the GitCommand program to always capture the output for stdout
and stderr.  And by default print the output while running.

The options capture_stdout and capture_stderr have effectively become
options to supress the printing of stdout and stderr.

Update the 'git fetch' to use '--progress' so that the progress messages
will be displayed.  git checks if the output location isatty() and if it
is not a TTY it will by default not print the progress messages.

Change-Id: Ifdae138e008f80a59195f9f43c911a1a5210ec60
2 files changed