How does merging work in TFS 2010?

When I merge files from one branch to another and then go to check in files into the target branch, there are MANY files checked out, just the ones that changed. For example, Main and Critical branches were the same and we made changes to only 2 or 3 files on the Critical Fix branch. I then merged Critical ==> Main, and when I went to check in changes to the Main branch I noticed that there were numerous files checked out, not just the 2 or 3 that we开发者_如何学运维re actually changed in the Critical Fix branch. Moreover, when I compare a file from the Main branch to one on the server, I am told that the files are identical. If the files are identical, why are they checked out? Any help would be appreciated, or even a link that explains how TFS 2010 does merges.

The default Source Control Merging tools in Visual Source Safe and then TFS have always been rather poor - they are often confused by the simplest changes, often detect identical files as being "changed", and the auto-merge facility frequenty fails (includes the wrong changes). I quickly learned distrust for these merge tools (in about 1995) and have not seen any evidence in any of the new releases since then that the core merge algorithms have been improved at all.

The good news is that you can replace the client-side merging tools with third party ones (I use one that works so well that I actually trust its auto-merge option. I once spent 2 days trying (and failing) to do a complex merge with the TFS tools and in the end bought this 3rd party tool and re-did the entire merge successfully in 15 minutes!)

The bad news is that the first step of branch merging just uses the TFS merge code, and so it gets confused a lot, resulting in the symptoms you've described. This is frustrating in such a key feature of such an expensive application as it wastes a lot of programmer time on every merge to fix imaginary "conflicts" - on the plus side, with the help of 3rd party tools it is usually very easy to reliably resolve these merge issues.

I have had the same problem. I created a branch of our DEV branch and made changes to a few files. I checked in my changes and merged the latest changes to DEV into my branch. After the merge all 30,000+ files in my branch were marked as changed. Just like cju, I found that a comparison of most of the files showed that no changes had been made.

I decided to undo all changes and try again. When I right-clicked on the solution and selected Undo, I got a message that one file had changes, was I sure I wanted to undo that file? I clicked "No to All" and when the undo operation was complete, only the files that had been changed during my merge from DEV were still checked out. This was exactly what I wanted so I checked those changes into my branch and continued working.

I hope others can correct their situation as easily as I was able to.

One thing I noticed is that when one file is changed in different branches resulting in exactly the same content, then merging marks it as a conflict since the file is changed in both places. Of course a difference view of the file notices that there are no changes and therefore an auto merge solves this automatically for you.