In this article we will configure winmerge as diff and merge tool in git but you can configure any other tool with same way. Before we start, make sure you have winmerge installed on your machine, you can download from here. You can configure external diff and merge tool by git bash commands as show below. Note about file extensions: Git doesn't allow to configure external tools by extension (as Tortoise Git does). So if you configure the SemanticMerge, it will be run for all files when you decide to launch 'external diff or merge tool'. I use Git, SourceTree and Xcode on a Mac Lion machine. But I think I need an 'External Diff' tool. On git merge conflicts, ST fails to launch the external merge tool. Caesar cipher java code. Tried with FileMerge and Kaleidoscope and custom command. The four files LOACL, BASE, REMOTE, BACKUP are created though. External diff works fine.

Edit onlineThe file comparison tool can be integrated with Sourcetree so that you can use it to compare changes. The advantages of doing this include:

The OxygenCompare Files tool presents the files side-by-side and makes it much easier to determine real changes.
The OxygenCompare Files tool includes XML comparison algorithms.
The OxygenCompare Files tool includes various options for configuring the comparison.
The OxygenCompare Files tool allows you to navigate through changes.

To integrate the Compare Files tool with Sourcetree, follow this procedure, depending on your operating system:

Windows

In Sourcetree, go to Tools > Options.
Go to the Diff tab.
In the External Diff/Merge section, configure the settings as follows:
- External Diff Tool - Select Custom.
- Diff Command - Enter the path of the OxygendiffFile.exe file (for example: c:ProgramsOxygen XML Editor 19diffFiles.exe).
- Arguments - Enter -ext $REMOTE $LOCAL $LOCAL.
- Merge Tool - Select Custom.
- Diff Command - Enter the path of the OxygendiffFile.exe file (for example: c:ProgramsOxygen XML Editor 19diffFiles.exe).
- Arguments - Enter -ext $LOCAL $REMOTE $BASE $MERGED.
Click OK.

Result: In Sourcetree, you can now compare file changes with the OxygenCompare Files tool by simply selecting External Diff from the contextual menu, Actions menu, or Ctrl+D.

macOS

In Sourcetree, go to Sourcetree > Preferences.
Go to the Diff tab.
In the External Diff/Merge section, configure the settings as follows:
- External Diff Tool - Select Custom.
- Diff Command - Enter a command-line argument to launch the OxygendiffFiles.sh file (for example: sh '/Applications/Oxygen XML Editor/diffFiles.sh').
- Arguments - Enter -ext $REMOTE $LOCAL $LOCAL.
- Merge Tool - Select Custom.
- Diff Command - Enter a command-line argument to launch the OxygendiffFiles.sh file (for example: sh '/Applications/Oxygen XML Editor/diffFiles.sh').
- Arguments - Enter -ext $LOCAL $REMOTE $BASE $MERGED.
Close the preferences dialog box.

Result: In Sourcetree, you can now compare file changes with the OxygenCompare Files tool by simply selecting External Diff from the contextual menu or Actions Anime like slime tensei. menu.

Configuring SemanticMerge to be used as diff and merge tools for Git is rather simple. There are two options:

Configure it by using the git config commands.
Configure it by editing the .gitconfig file on your operating system.

Configure using `git config` commands

In order to configure SemanticMerge we will run the following commands:

Configure diff:

Which will produce the following .gitconfig file (except the [user] part that I added for completeness):

To invoke SemanticMerge as a diff tool, we're using the following command line:

semanticmergetool.exe -s $LOCAL -d $REMOTE

Whenever you run the semanticmergetool with only two params (left and right of the diff), it will work as a diff tool.

Run the following command to get help about the available params:

semanticmergetool -h

We enclose $REMOTE and $LOCAL (git params) in quotation marks to make sure the command is correctly invoked even if the paths contain spaces.

Important note: We used the C:/Users/pablo/AppData/Local/semanticmerge/ path for SemanticMerge. You will, obviously, have to replace the path with the right one where the semanticmergetool.exe is located in your computer.

Remark: Note that we run the command git config --global difftool.prompt false which will affect to all the difftools. This command means that whenever you run git difftool it won't ask you whether you really want to run the tool which we consider very annoying, but it is up to you to include this option according to your preferences.

Text diff: Using this configuration, SemanticMerge will use the included text based diff tool (called Xmerge) to compare the bodies of elements and text blocks. You can configure SemanticMerge to use any external tool you want. Check the Configuring external text diff and merge tools section for more information.

Configure mergetool:

Which will produce the following .gitconfig (except the [user] part that I added for completeness):

To invoke SemanticMerge as a merge tool, we're using the following command line:

semanticmergetool.exe -s $REMOTE -d $LOCAL -b $BASE -r $MERGED

Where $REMOTE, $LOCAL, $BASE and $MERGE are git params with the following meaning:

$REMOTE - It's the file you're merging (also known as 'theirs' or 'source'. 'source' is the name we use internally, that's why the param is -s).
$LOCAL - It's the file you're merging to (a.k.a. 'yours' or 'destination'. 'destination' is the name we use internally, that's why the param is -d).
$BASE - The common ancestor of the two files. Git calculates the right common ancestor (or base) using its internal merge algorithms and does a good job (although our own Plastic SCM does even a better one :P).
$MERGED - The file where the merge result will be written.

Remark: Please note that we configured two global merge settings that we consider useful:

But it is up to you to use them or not.

prompt means git won't ask you to confirm that you really want to launch an external tool when you run git mergetool to solve a merge.
keepBackup means git won't store .orig files.

Text merge and diff: By using this configuration, SemanticMerge will use the included text based diff and merge tool (called Xmerge) to compare the bodies of elements and text blocks and merge them. You can configure SemanticMerge to use any external tool you want. Check the Configuring external text diff and merge tools section for more information.

Configure editing the `.gitconfig` file

The final result is equivalent to running the commands, but you might prefer

Configure using git config commands

Configure diff:

Configure mergetool:

Configure editing the .gitconfig file

Configure using `git config` commands

Configure editing the `.gitconfig` file

Launch External Merge Tool For Sourcetree