TFS 2013 - no option to merge when resolving conflicts

Question

I'm doing some tests with TFS prior to moving all of our source there. Right now, I've created a very simple solution and I've set two workspaces, one local and one in the server.

With both workspaces on the last version, I've made some changes in the server workspace and checked them in. Then, I've made some other changes in the local workspace and I've tried to check them in too. Of course, there is a conflict, but I only get the option to keep the local changes or take the version from the server. I would expect to see an option to merge the different changes.

I'm pretty sure I've seen the option to merge before, in some other tests I did some time ago...

Any solutions? Am I doing something wrong?

UPDATE: I've clicked in the "Annotate" button and it tells me it can't be done because the file TestApp.cpp is a binary file (Error TF206000). Maybe I should add that I've moved the files from git via git-tf. However, the file on my computer seems fine, ANSI-coded, with CRLF line endings, and no strange looking characters in notepad++, or any other editor I've opened it in...

UPDATE 2:
Answering MartW's comment: The file on the server looks the same as on my PC. Well, there seems to be some encoding issue, since the accents are not shown properly. Also, it doesn't let me annotate the file on the server through the browser, with this error: "Valid values are between 0 and 65535, inclusive. Parameter name: codepage".

I've checked through the versions, and I can annotate the first one where the file appears. All the rest give the same error.

Answer 1

OK, I think I found it. Apparently, TFS has decided that all my files are binary files. By going to the Source Code Explorer, selecting the file, opening the context menu and selecting Advanced|Properties, I've been able to change the encoding (actually, if I tell it to auto-detect it, it does it just fine) and now I can merge...
Now, I have to find how to change the encoding of all the files (well, just text files) at once.

Answer 2

Whether merging or not is available for a particular file type is dependant on the file extension, and controllable via the TFS Source Collection settings. In TFS 2013, this can be accessed from within Visual Studio and selecting Team => Team Project Collection Settings => Source Control. You'll see a list of various file types and associated extensions, along with whether file merging is enabled for those types. CPP files are under the C++ section and should say Enabled - perhaps this is Disabled in your setup?