add a global --color option

If you want to turn off colors for commands, you have to manually adjust
the git config settings (in various locations).  If you're writing scripts
though, you often don't want to modify those locations.  Add a commandline
option to explicitly control things.

The default behavior is unchanged -- we still scan the config files.

Change-Id: I54a3fd8e1918bac180aadd7c7d3004f069b02522

2 files changed, 31 insertions, 2 deletions

diff --git a/color.py b/color.py
index 7970198a..b2799286 100644
--- a/color.py
+++ b/color.py
@@ -83,15 +83,38 @@ def _Color(fg = None, bg = None, attr = None):
   return code
 
 
+DEFAULT = None
+
+def SetDefaultColoring(state):
+  """Set coloring behavior to |state|.
+
+  This is useful for overriding config options via the command line.
+  """
+  if state is None:
+    # Leave it alone -- return quick!
+    return
+
+  global DEFAULT
+  state = state.lower()
+  if state in ('auto',):
+    DEFAULT = state
+  elif state in ('always', 'yes', 'true', True):
+    DEFAULT = 'always'
+  elif state in ('never', 'no', 'false', False):
+    DEFAULT = 'never'
+
+
 class Coloring(object):
   def __init__(self, config, section_type):
     self._section = 'color.%s' % section_type
     self._config = config
     self._out = sys.stdout
 
-    on = self._config.GetString(self._section)
+    on = DEFAULT
     if on is None:
-      on = self._config.GetString('color.ui')
+      on = self._config.GetString(self._section)
+      if on is None:
+        on = self._config.GetString('color.ui')
 
     if on == 'auto':
       if pager.active or os.isatty(1):
diff --git a/main.py b/main.py
index 72fb39b0..47f083df 100755
--- a/main.py
+++ b/main.py
@@ -36,6 +36,7 @@ try:
 except ImportError:
   kerberos = None
 
+from color import SetDefaultColoring
 from trace import SetTrace
 from git_command import git, GitCommand
 from git_config import init_ssh, close_ssh
@@ -69,6 +70,9 @@ global_options.add_option('-p', '--paginate',
 global_options.add_option('--no-pager',
                           dest='no_pager', action='store_true',
                           help='disable the pager')
+global_options.add_option('--color',
+                          choices=('auto', 'always', 'never'), default=None,
+                          help='control color usage: auto, always, never')
 global_options.add_option('--trace',
                           dest='trace', action='store_true',
                           help='trace git command execution')
@@ -113,6 +117,8 @@ class _Repo(object):
         print('fatal: invalid usage of --version', file=sys.stderr)
         return 1
 
+    SetDefaultColoring(gopts.color)
+
     try:
       cmd = self.commands[name]
     except KeyError: