repo/init/sync: rework default git download output

When we download git sources, we get a progress bar (good) and we get
a dump of all the refs we downloaded (bad) as it can easily be 100+ if
not 1000+ depending on the project (for each git repo!).  Lets rework
the output behavior so that:
* quiet: Only errors.
* default: Progress bars (if on a tty).
* verbose: Full output (progress bars & downloaded refs).

Bug: https://crbug.com/gerrit/11293
Change-Id: I87a380075e79de6805f91095876dd1b37d32873a
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/256456
Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Michael Mortensen <mmortensen@google.com>

repo

@@ -758,15 +758,17 @@ def _InitHttp():
 
 def _Fetch(url, cwd, src, quiet, verbose):
   cmd = ['fetch']
-  if quiet:
+  if not verbose:
     cmd.append('--quiet')
+  err = None
+  if not quiet and sys.stdout.isatty():
+    cmd.append('--progress')
+  elif not verbose:
     err = subprocess.PIPE
-  else:
-    err = None
   cmd.append(src)
   cmd.append('+refs/heads/*:refs/remotes/origin/*')
   cmd.append('+refs/tags/*:refs/tags/*')
-  run_git(*cmd, stderr=err, cwd=cwd)
+  run_git(*cmd, stderr=err, capture_output=False, cwd=cwd)
 
 
 def _DownloadBundle(url, cwd, quiet, verbose):