Reland - Support msysgit in gcl and git-cl

An explicit msysgit check is needed since it requires
the usage of 'env' to open the editor.

BUG=70550, 70548
TEST=Win,Linux 
Review URL: http://codereview.chromium.org/6680019

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@77946 0039d316-1c4b-4281-b951-d872f2087c98

gcl.py

@@ -1063,11 +1063,18 @@ def CMDchange(args):
   os.write(handle, text)
   os.close(handle)
 
-  if not silent:
-    os.system(GetEditor() + " " + filename)
-
-  result = gclient_utils.FileRead(filename, 'r')
-  os.remove(filename)
+  # Open up the default editor in the system to get the CL description.
+  cmd = [GetEditor(), filename]
+  if sys.platform == 'win32' and 'mingw\\bin' in os.environ['PATH']:
+    # Msysgit requires the usage of 'env' to be present. The only way to
+    # accomplish that is by reading the environment variable for mingw\bin.
+    cmd.insert(0, 'env')
+  try:
+    if not silent:
+      subprocess.check_call(cmd)
+    result = gclient_utils.FileRead(filename, 'r')
+  finally:
+    os.remove(filename)
 
   if not result:
     return 0

git_cl/git_cl.py

@@ -710,9 +710,14 @@ def UserEditedLog(starting_text):
   fileobj.write(starting_text)
   fileobj.close()
 
-  result = None
+  # Open up the default editor in the system to get the CL description.
+  cmd = [editor, filename]
+  if sys.platform == 'win32' and 'mingw\\bin' in os.environ['PATH']:
+    # Msysgit requires the usage of 'env' to be present. The only way to
+    # accomplish that is by reading the environment variable for mingw\bin.
+    cmd.insert(0, 'env')
   try:
-    subprocess.check_call(['env', editor, filename], shell=True)
+    subprocess.check_call(cmd)
     fileobj = open(filename)
     result = fileobj.read()
     fileobj.close()