File permissions seen incorrectly through a Samba map

I have Ubuntu 12.04.3 in a VMware VM on the same machine with root mapped through Samba:

[root]
comment = localDev System Root
path = /
writeable = yes
browseable = yes
valid users = devuser
force user = root
force group = root
create mask = 0644
directory mask = 0755

I have a Git repo on Ubuntu which is clean (no pending changes indicated with 'git status'). When I view that repo through the Samba map in SoucreTree, three files are indicated as changed. The change is in permissions: "Modified file, mode 10755->100644". The files in question are set executable, so 10755 is the correct permissions – they have not been changed to 100644. Maybe Samba modifies the executable flag so that SourceTree sees it as 100644? If that is the case, it would be good to add an option to not track changes in file permissions if the problem can't be otherwise fixed.