can't open external merge tool

Using Lion, I have no problems running opendiff from the terminal. But choosing "Launch External Merge Tool" from Sourcetree shows me a brief window notifying me that I'll need to quit the external merge tool to complete the merge process, then the window closes and the merge tool is never launched.

4 answers

1 accepted

1 vote
Answer accepted

My guess is you've updated your PATH to find opendiff so it works from the terminal, but PATH is not used by GUI apps in OS X.

Please refer to this KB article which should solve your problem:

Still no go. I added


to /etc/paths and I added

export PATH=${PATH}:/Developer/usr/bin

to ~/.bash_profile

Still the same problem

Did you restart as per the notes? Also, the first option (symlinking) is faster.

I'm re-installing developer tools just in case that helps. Any ideas are welcome. Thanks.

Hmm, that's odd then - if it's in /usr/bin it should work (that will have been from a previous install). You can make sure that works by calling /usr/bin/opendiff manually, and if it doesn't work, remove it and symlink to the newer one instead.

Otherwise, you could check your ~/.gitconfig to make sure that opendiff is being used there (assuming this is git)

Yes, I restarted. On my mac, opendiff exists (not a symlink) at both locations (/usr/bin and /Developer/usr/bin) so terminal refused to symlink from one to the other. The opendiff in /Developer/usr/bin is from May 2011. The one in /usr/bin is from December 2011. Strange.

running /usr/bin/opendiff manually works. ~/.gitconfig has these lines:

[difftool "sourcetree"]

	cmd = opendiff \"$LOCAL\" \"$REMOTE\"

	path = 

[mergetool "sourcetree"]

	cmd = /Applications/ \"$LOCAL\" \"$REMOTE\" -ancestor \"$BASE\" -merge \"$MERGED\"

	trustExitCode = true

and the file within the Sourcetree app path has the following:


opendiff "$@" | cat

by the way, external diff works fine. it's just external merge that won't run.

Hmm, that all looks fine, and if the External Diff is working then SourceTree can see opendiff OK.

I just ran a couple of tests here and merging with FileMerge is working for me on 1.4.4.x both on merge conflicts and rebase conflicts. Can you give some more detail on the file that's being merged? Is it possible that there's actually nothing that needs merging? Git will not bother to launch the tool if so.

Thanks Steve. I'm new to Git, using it to develop a wordpress site. Perhaps I'm doing something wrong.

In essence, I'm trying to resolve conflicts after a merge using the external merge tool.

In more detail, here's the path I've taken as a Git novice trying to merge with conflicts: I merged one branch into another, and wound up with about 19 conflicts. I started sifting through the conflicts using the Sourcetree GUI, discarding and staging changes, but staged changes created artifacts like this: "<<<<<<< HEAD" in the files. After a lot of googling, I found no answer as to why I should have to remove these by hand, and so I'm running on the assumption that using the external merge tool won't leave these artifacts.

Any advice would be appreciated. Thank you for replying so promptly.

That's right - the 'chevrons' are there to indicate conflicts, and you can edit the files manually to remove the conflicts (basically the section between <<<<<< and ======== is one side, then from ======== to >>>>>>> is the other), subsequently using 'Mark resolved' to indicate you've fixed the conflict, or you can use an external merge tool to get a more user-friendly view of it.

I've never seen this fail for FileMerge when the tool is correctly launchable so I'm short of ideas now - the presence of the chevrons indicates there is in fact something to resolve. Again I've tested this here with a merge conflict and rebase conflict and all is as expected.

Just one thing to check: in Preferences is the box "Allow SourceTree to modify your global Mercurial and Git files" checked? Your .gitconfig indicates it was checked at one point, but if it's been unchecked since then then SourceTree assumes you've configured the external merge tools yourself.

If it is checked, you might get more information by running this on the command line:

git mergetool -y --tool=sourcetree -- filename

Okay, I tried that command with a file that had a conflict and this is what I got back (I replaced the long path in the response with /path/to)

Normal merge conflict for 'footer.php':
  {local}: created
  {remote}: created
2012-06-18 09:57:31.848 opendiff[16037:c07] /path/to/footer.php.BASE.15978.php does not exist

The command created an edited footer.php and a footer.php.orig. It didn't launch anything, and running the command took footer.php out of the conflicts list in Sourcetree.

Sourcetree also creates a new copy and an original copy when i try to use the external merge tool, but then nothing happens and the file stays in the conflicts list.

Also, does using the external merge tool make it easy to get rid of all the chevron markers or does that still have to be done manually? Seems tedious.

One added piece of info, Steve: I don't know if it's normal but every time I click resolve using external merge tool, console produces a message like this:

opendiff: /path/to/footer.php.BASE.30697.php does not exist

Just like I got with the terminal command you suggested.

Yes, the external merge tool means you don't have to deal with the chevrons yourself. Some people like to just resolve these things with a text editor though, which is why they're there.

About the 'does not exist' error, at least I know this isn't a SourceTree problem then since naked git does it too. This usually only happens if one side of the merge doesn't exist, which might be because one or other side of the merge deleted it, or perhaps moved the file. While git does try to be sensible with renamed files, merges often can't handle files moving around very easily, it's usually best to avoid them. You may have to resolve this case manually if that's the issue, but it's worth noting that this is not a commonplace occurrence, usually the visual merge is very easy to use to resolve this.

Thanks for working through this with me, Steve. You're right: I set up a little test repo and had no problem launching the external merge tool.

Any thoughts as to why this is happening with the project I'm working with?

My guess would be that it's the file itself, either a rename or a deletion on one side of the merge.

thanks, yes, i worked it out. thanks for your help.

One cause of this problem is that SourceTree fails to quote the path to the helper script, which in my case is at ~/Library/Application Support/SourceTree/...

The space between Application and Support causes SourceTree to fail to launch the helper.

In my .gitconfig, I manually added \" surrounding the path-to-helper part, and things are back to working for me.


The issue on my machine was that the `opendiff` utility was confused by some misconfiguration of XCode. It looked like that:


$ opendiff
xcode-select: error: tool 'opendiff' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance

The solution was to run 

$ sudo xcode-select -s /Applications/

Replace /Applications/ by your XCode path, of course


Suggest an answer

Log in or Sign up to answer
Community showcase
Published Oct 23, 2018 in Sourcetree

Tip from the team: configure your repos for hosting goodness!

Supported Platforms macOS Windows We recently introduced support for additional hosting services such as GitHub Enterprise, GitLab (Cloud, Community Edition, Enterprise Edition), and...

1,228 views 4 2
Read article

Atlassian User Groups

Connect with like-minded Atlassian users at free events near you!

Find a group

Connect with like-minded Atlassian users at free events near you!

Find my local user group

Unfortunately there are no AUG chapters near you at the moment.

Start an AUG

You're one step closer to meeting fellow Atlassian users at your local meet up. Learn more about AUGs

Groups near you