Tutorial: Use IntellJ IDEA as default command-line merge tool

Locate the .gitconfig and add the following configuration, based on your operating system:

[merge]
tool = intellij
[mergetool "intellij"]
cmd = 'C:/Program Files/JetBrains/IntelliJ IDEA/bin/idea64.exe' merge "$LOCAL" "$REMOTE"
"$BASE" "$MERGED"
trustExitCode = true
[mergetool]
keepBackup = false

[merge]
tool = intellij
[mergetool "intellij"]
cmd = '/Applications/IntelliJ IDEA.app/Contents/macOS/idea' merge “$LOCAL” “$REMOTE” “$BASE”
“$MERGED”
trustExitCode = true
[mergetool]
keepBackup = false

[merge]
tool = intellij
[mergetool "intellij"
cmd = '/opt/idea/bin/idea.sh' merge “$LOCAL” “$REMOTE” “$BASE” “$MERGED”
trustExitCode = true
[mergetool]
keepBackup = false

By default, Git keeps a copy of the file's contents before resolving conflicts. After a merge, Git saves the original file with the conflict tags with a .orig extension. This file will not be preserved if you set the variable keepBackup to false.

Quit editing the .gitconfig.

Create a simple Java class.

You can use the following sample code:

public class MyClass {
    public static void main(String[] args) {
        System.out.println("one");
        System.out.println("two");
    }
}

Commit your changes to the master branch.

Check out a new branch from the master branch, we will call ours feature1, and change your MyClass.java.

Check out the master branch again and change your MyClass.java one more time.

Try merging feature1 into master from the command line:

git merge feature1

You will get a conflict stating that you have unmerged files.

Run git mergetool.

RubyMine will automatically start and open the merge tool to resolve the conflicts.

In the three-way merge dialog, select the pane from which you want to apply changes and press Accept Left or Accept Right in the gutter.

In our case, we choose the changes from our feature1 branch on the right.

Click Apply.

Run the cat command in the file where you resolved the merge conflict in the terminal, and look at the merge result.