How to use SourceGear DiffMerge in SourceSafe, TFS, and SVN

What is DiffMerge

DiffMerge is yet-another-diff-and-merge-tool from the fine folks at SourceGear.  It’s awesome.  It’s head and shoulders above whatever junky diff tool they provided with your source control platform, unless of course you’re already using Vault.  Eric Sink, the founder of SourceGear, wrote about it here.  By the way, Eric’s blog is easily one of the most valuable I’ve read, and while it doesn’t get much love these days, there’s a lot of great stuff there, and it’s even worth going back and reading from the beginning if you haven’t seen it.

Are there better diff tools out there?  Sure, there probably are.  I’m sure you have your favorite.  If you’re using something already that works for you, great.  DiffMerge is just yet another great option to consider when you’re getting started.

You sound like a sleazy used car salesman

Yeah, I probably do, but I don’t work for SourceGear and have no financial interest in their products.  I’ve just been a very happy user of Vault and DiffMerge for years.  And it if increases Vault adoption, both among development shops and development tool vendors, it will make my life easier.

But when I go to work on long-term contracts for large clients, they already have source control in place that they want me to use, which is OK, but when I need to do some merging, it starts getting painful.  I want it to tell me not just that a line changed, but exactly what in that line changed.  I want to it actually be able to tell me the only change is whitespace.  I want it to offer me a clean and intuitive interface.  Crazy, I know.

Not a huge problem because DiffMerge is free, and it can plug into just about any source control system, replacing the existing settings.  However those settings can be tricky to figure out, so I figured I’d put together a cheat sheet of how to set it up for various platforms.

Adding DiffMerge To SourceSafe

Let’s start off with those in greatest need, ye old SourceSafe users.  First and foremost, I’m sorry.  We all feel bad that you are in this position.  SourceSafe was great for what it was, 15 years ago when file shares were considered a reliable data interchange format, but nobody should have to suffer through SourceSafe in this day and age.  But don’t worry, adding in DiffMerge can add just enough pretty flowers to your dung heap of a source control system to make it bearable.  Just like getting 1 hour of yard time when you’ve been in the hole for a week, it gives you something look forward to.

Anywho, let’s get started.  First, whip out your SourceSafe explorer:


Here’s what we get for a standard VSS diff:


Ugh.  So go to Tools->Options and go to the Custom Editors Tab.  From there, the following operations:

Operation: File Difference

File Extension: .*

Command:  [DiffMergePath]\diffmerge.exe –title1=”original version” –title2=”modified version” %1 %2

Operation: File Merge

File Merge: .*

Command: [DiffMergePath]\diffmerge.exe –title1=”source branch” –title2=”base version” –title3=”destination branch” –result=%4 %1 %3 %2

Now here’s our diff, much less painful:


But merging is where it really shines:


Thanks to Paul Roub from Source Gear for the details:

Adding DiffMerge To Subversion

Obviously SVN is worlds better than VSS, but some of the standard tools distributed with TortoiseSVN are a little lacking.  You might say “you get what you paid for,” but you’d only say that if you wanted to tick off a lot of smart and helpful people.

So let’s take a look at a standard diff in SVN:


Oof.  I’ve used SVN on and off for years, and I still don’t understand what is going on here.

So let’s get this a little mo’ better.  Right click your folder, and select TortoiseSVN->Settings.  Go to the External Programs->Diff Viewer, and enter this External tool:

 [DiffMergePath]\DiffMerge.exe /t1=Mine /t2=Original %mine %base


Switch over to the Merge Tool screen, and enter this External Tool:

[DiffMergePath]\DiffMerge.exe /t1=Mine /t2=Base /t3=Theirs /r=%merged %mine %base %theirs


And now our diffs look a little more familiar:


Thanks Mark Porter for the details:

Adding DiffMerge To Team Foundation Server

For years I dreamed of using TFS.  I hoped that someday I would work at a company successful and cool enough to invest the money in a TFS solution.  And then I actually got it, and uh, it’s seems like a nice enough fella, but it seems that its tendencies towards megalomania have really had some negative consequences on the end-user experience.

Given that, after decades of technological advancement in source control, the TFS diff tool is pretty much just the same ugliness as SourceSafe:


Get your spelunking helmet on, and we’ll go digging for the settings in TFS to change this.

  • Open up Visual Studio and select Tools->Options
  • Expand the Source Control group, and select Visual Studio Team Foundation Server
  • Click the Configure User Tools button


Enter the following tool configurations:

Operation: Compare

Extension: .*

Command: [DiffMergePath]\DiffMerge.exe

Arguments: /title1=%6 /title2=%7 %1 %2

Operation: Merge

Extension: .*

Command: [DiffMergePath]\DiffMerge.exe

Arguments: /title1=%6 /title2=%7 /title3=%8 /result=%4 %1 %2 %3 (Corrected, thanks to Rune in the comments!)

Thanks to James Manning for the details:

The End

So that’s all it takes to make your source control life a little bit easier.  Even if you don’t prefer DiffMerge, I’d suggest you find one you do like, because the built-in tools are usually pretty bad.  Diffing and merging is hard enough as it is, don’t waste precious brain cells on substandard tools.

4 thoughts on “How to use SourceGear DiffMerge in SourceSafe, TFS, and SVN

  1. I much prefer WinMerge myself, but you DEFINITELY gotta have SOME kind of tool to allow advanced diffing/merging!

  2. The correct command line is this: (you want your version in the middle)
    /title1=%6 /title2=%7 /title3=%8 /result=%4 %1 %2 %3

  3. I disagree with rune. According to the DiffMerge help document (which has the settings listed for doing both compares and merges with TFS), the correct command line is: /m /r=%4 /t1=%7 /t2=%8 /t3=%6 /c=%9 %2 %3 %1

    This puts your version in the left panel, the server version in the right panel, and the merged version in the middle. This is how DiffMerge expects it to be so that you can do things like “Merge to Middle” with the tool.

  4. Steve is correct (in saying that rune is not correct ^^). The Merged file should be in the middle.

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