Restore Windows compatibility, which my shell escaping fix would have…

… broken.

Windows needs to go through the shell in order to find git on the PATH,
but it's OK to use the shell there because it will automatically escape
discrete arguments.

Warning: this is theoretical work. Untested on Windows.

gitmark.py

@@ -17,6 +17,12 @@
 
 from settings import *
 
+# Arguments are passed directly to git, not through the shell, to avoid the
+# need for shell escaping. On Windows, however, commands need to go through the
+# shell for git to be found on the PATH, but escaping is automatic there. So
+# send git commands through the shell on Windows, and directly everywhere else.
+USE_SHELL = os.name == 'nt'
+
 class gitMark(object):
 
     def __init__(self, options, args):
@@ -50,10 +56,10 @@ def __init__(self, options, args):
             self.gitPush()
 
     def gitAdd(self, files):
-        subprocess.call(['git', 'add'] + files)
+        subprocess.call(['git', 'add'] + files, shell=USE_SHELL)
 
     def gitCommit(self, msg):
-        subprocess.call(['git', 'commit', '-m', msg])
+        subprocess.call(['git', 'commit', '-m', msg], shell=USE_SHELL)
 
     def gitPush(self):
         pipe = subprocess.Popen("git push origin master", shell=True)