Echo stderr of subcommands that do network IO when --verbose is used

Morph can appear to hang in situations where it is actually waiting on a
slow network operation. This change gives users a way to see the output
of the subcommands that are doing the network IO (either 'wget', 'git
clone' or 'git remote update').

The status information goes onto stderr, because that is where the
subcommands write it. Morph tends to put its status output on stdout,
but (a) some commands are machine-parsed, such as `serialise-artifact`
and (b) it's tricky to get Git to put status output on stdout.

1 files changed, 11 insertions, 0 deletions

diff --git a/morphlib/git.py b/morphlib/git.py
index d897de3b..70222acb 100644
--- a/morphlib/git.py
+++ b/morphlib/git.py
@@ -22,6 +22,7 @@ import os
 import re
 import string
 import StringIO
+import sys
 import time
 
 
@@ -333,6 +334,16 @@ def gitcmd(runcmd, *args, **kwargs):
     # is enough to say what it contains, so we turn it off by setting
     # the right flag in an environment variable.
     kwargs['env']['GIT_NO_REPLACE_OBJECTS'] = '1'
+
     cmdline = ['git']
+
+    echo_stderr = kwargs.pop('echo_stderr', False)
+    if echo_stderr:
+        if 'stderr' not in kwargs:
+            # Ensure status output is visible. Git will hide it if stderr is
+            # redirected somewhere else (the --progress flag overrides this
+            # behaviour for the 'clone' command, but not others).
+            kwargs['stderr'] = sys.stderr
+
     cmdline.extend(args)
     return runcmd(cmdline, **kwargs)