Source control could not start the manual merge tool, why?

Question

I used to execute tf merge $/Alpha/Dev $/Alpha/Main /recursive from Command Prompt to merge changes from Dev branch to Main branch. On conflicts it shows up Resolve Conflicts window and we could resolve conflicts manually by choosing option Merge changes in Merge Tool

It was working fine till yesterday, all of a sudden it started throwing below error, and not showing the manual merge window.

TF10201 Source control could not start the manual merge tool.

One strange behavior, it is working fine if we open the Command Prompt as administrator.

Please anyone shed some light on this?

Answer 1

HOW TO RESTORE THE MICROSOFT DEFAULT MERGE TOOL

If you are having any problems with a diff/merge tool in Visual Studio and you are using TFS you can delete your existing tool in the menu here:

TOOLS - OPTIONS - SOURCE CONTROL - VISUAL STUDIO TEAM FOUNDATION SERVER

Then click the button entitled "Configure User Tools" Select the Tool(s) and hit the REMOVE button. This will restore the Microsoft default tool.

Answer 2

I got the same error because my local file in target branch was missing. VS shows error details in "output window"

Answer 3

I was running tf get and I had a conflict so the GUI displayed choices of take server, merge, take local.

When I clicked manual merge, VS2012 (our default merge tool) came up blank, and the conflict GUI had that same TF10201 Source control could not start the manual merge tool.

I found a blog post by somebody who had the same problem a few weeks ago, where they got a warning that the file was open.

I didn't get that warning, but I had the file open in PowerShell ISE. I closed the file, and then the manual tool worked perfectly.

I don't know why the merge tool cares that the file was open, or why the merge GUI displayed the error without displaying the reason, but at least it worked eventually?

EDIT: I hit the same issue today, without the file open in another merge tool. This time, I fixed the problem by first clicking the "Server edits" button, which opened the diff view in VS. While that was open I went back to the GUI and chose "manual tool" and VS said it had to close my file first. I said yes, and then manual merge worked!