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A note on merging and the use of TF MERGES & TF MERGE

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Have you ever had to do any forensic work on TFS merges, tracking down what you or a member of your team has done? For example, when changes have been merged into a branch and an attempt is made to merge again with the same source and target, TFS may respond with “No changes to merge”.  This may be expected, but you might like to see what TFS already knows with regards to which changesets have already been merged. That is just one example of something you may need to investigate. Recently, Philip Kelley from the TFS dev team provided this little write-up on that type of work. I present it now for your reading pleasure. Hopefully it will help with the sleuthing! :-)

-Trev

 

The way to answer questions like this is with the “tf merges” command and the “tf merge /candidate” command.

“tf merges $/Source/file.txt $/Target/file.txt” asks the question, “What changesets have I already merged from $/Source/file.txt to $/Target/file.txt? What changeset was each merge committed in in the target?” You get output a bit like this.

D:\>tf merges $/Source/File.cs $/Target/File.cs

Changeset            Merged in Changeset   Author                           Date

--------- ------------------- -------------------------------- ---------- ----------

  437213               500301                     REDMOND\asdfasdf          7/19/2008

  559688               600202                     REDMOND\asdfasdf          10/15/2008

  683776               708113                     REDMOND\dddddd            1/16/2009

  704497               706112                     REDMOND\asdfasdf           1/14/2009

  714056               727413                     REDMOND\dddddd            1/31/2009

  786117               788339                     REDMOND\asdfasdf           3/17/2009

So here we can see that changeset 437213 to $/Source/File.cs was successfully merged to $/Target/File.cs in changeset 500301 (on 7/19/2008). Etc.

“tf merge /candidate $/Source/file.txt $/Target/file.txt” asks the question, “What changesets in the source have I not merged to the target yet – that is, which ones are eligible for merging?” Here again is some sample output.

D:\>tf merge /candidate $/Source/File.cs $/Target/File.cs

Changeset Author                           Date

--------- -------------------------------- ----------

  751713  REDMOND\lalalal                  2/20/2009

Here we see a single changeset eligible for merging to the target. If I say “tf merge $/Source/File.cs $/Target/File.cs” then I will see a merge pended which brings this changeset to the target. If I say “tf merge $/Source/File.cs;C700000 $/Target/File.cs” then I am asking for eligible changesets in the range 1-700000 to be merged and 751713 is outside of this range, so I’ll see “No changes to merge.”

Any time these merge history tables are going to be updated by a change, you will see the “merge” bit pending on the item. This indicates that some sort of credit is being given for a merge. At least one new line will show up in “tf merges” as a result of the changeset.

You can give credit for a merge without actually taking the content changes. This is the purpose of the /discard switch to tf merge – it says, pend a change in the target which gives credit for some changes, but does not actually bring them to the target branch. You can also accomplish the same thing when there’s a conflict by selecting “Keep target version.” This gives credit for the changeset merging over but leaves the content alone. In both cases you’ll see a “merge” change standing alone. In future merges this change will not come over again.

If you’ve given credit for a changeset already and want to merge it “again” – maybe I wanted to bring changeset 786117 from $/Source/File.cs to $/Target/File.cs again – then I could use the /force option to tf merge. The /force says, ignore the merge history that says the change(s) are already in the target. I want you to bring them over again. You can do this for a range of changesets or just a particular one. For just 786117 I would say “tf merge /force $/Source/File.cs;C786117~786117 $/Target/file.cs”.

 

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