How to use the command 'git mergetool' (with examples)

The git mergetool command is a powerful utility in Git’s toolkit that assists developers in resolving merge conflicts by invoking external merge resolution tools. Merge conflicts occur when combining changes from different branches or from remote and local repositories. The git mergetool can simplify the process of choosing between conflicting changes, merge edits, and ensure that your project remains consistent and functional.

Use case 1: Launch the default merge tool to resolve conflicts

Code:

git mergetool

Motivation:

Using the default merge tool can be a time-saver, as it provides a standardized environment to resolve merge conflicts. Developers might find it convenient because it opens a familiar interface for handling files with merge conflicts, ensuring a more intuitive and streamlined conflict-resolution process.

Explanation:

• git: This invokes the Git command line interface.
• mergetool: This specific command triggers the merge tool configuration to handle file conflicts that arise during a merge.

Example Output:

Merging:
file1.txt
Normal merge conflict for 'file1.txt':
  {local}: modified file
  {remote}: modified file
Hit return to start merge resolution tool (opendiff):

Use case 2: List valid merge tools

Code:

git mergetool --tool-help

Motivation:

Listing all valid merge tools helps developers understand which external tools are available and compatible with their existing setup. This information can guide the choice of the most suitable tool according to a developer’s preferences and project requirements.

Explanation:

• git: Invokes the Git command line interface.
• mergetool: Initiates the command to handle merge conflicts.
• --tool-help: An option that displays information about available and compatible merge tools that can be configured with Git.

Example Output:

'vimdiff'          available
'kompare'          available
'meld'             available
'opendiff'         available
'artmeld'          available

Use case 3: Launch the merge tool identified by a name

Code:

git mergetool --tool tool_name

Motivation:

Sometimes, developers prefer specific tools for their user interface or functionality. Using a named tool allows for customization, enabling developers to work with the tool they find most effective for their workflow.

Explanation:

• git: Invokes Git’s command line interface.
• mergetool: Launches the merge tool feature.
• --tool: Option that specifies the particular external merge tool to use.
• tool_name: A placeholder for the actual name of the tool you want to use. It needs to be replaced with the name listed by the --tool-help command.

Example Output:

Merging:
file1.txt
Normal merge conflict for 'file1.txt':
  {local}: modified file
  {remote}: modified file
Hit return to start merge resolution tool (meld):

Use case 4: Don’t prompt before each invocation of the merge tool

Code:

git mergetool --no-prompt

Motivation:

By eliminating prompts, the merge tool begins immediately, making the process faster especially when numerous conflicts exist. This is particularly useful in large projects where resolving multiple conflicts is necessary.

Explanation:

• git: This invokes Git’s command-line interface.
• mergetool: Activates the merge tool functionality to resolve conflicts.
• --no-prompt: An option that automatically starts the merge tool without waiting for user confirmation via prompts.

Example Output:

Merging:
file1.txt

(The merge tool opens directly without prompts, starting the conflict resolution process.)

Use case 5: Explicitly use the GUI merge tool

Code:

git mergetool --gui

Motivation:

Some users prefer graphical interfaces for ease of use and better visualization of conflicts. This command ensures that the merge tool’s graphical version is used, providing an intuitive experience with visual aids to resolve conflicts effectively.

Explanation:

• git: Boots up the Git command line interface.
• mergetool: Triggers the merge tool command.
• --gui: An option that forces Git to use the GUI version of the merge tool configured in merge.guitool.

Example Output:

Launching GUI merge tool:
Merging:
file1.txt

(The GUI merge tool’s window opens to allow visual conflict resolution.)

Use case 6: Explicitly use the regular merge tool

Code:

git mergetool --no-gui

Motivation:

When working in environments or setups where GUI applications are unavailable or not preferred, one might opt for a text-based interface. This command ensures that the regular, non-GUI version is utilized, best for situations requiring remote access or command-line only interfaces.

Explanation:

• git: Invokes the Git command-line interface.
• mergetool: Commences the utility to tackle merge issues.
• --no-gui: Forces Git to use the non-GUI version of the selected merge tool, as determined by merge.tool configuration.

Example Output:

Merging:
file1.txt
Normal merge conflict for 'file1.txt':
  {local}: modified file
  {remote}: modified file

(The non-GUI merge tool interface opens in the terminal to allow manual resolution.)

Conclusion:

The git mergetool command is highly versatile and configurable to accommodate various user preferences and computing environments. From graphical interfaces for easy visualization to prompt-free operations for efficiency, Git provides numerous ways to integrate merge tools and resolve conflicts adeptly. By exploring these use cases, developers can streamline their workflow, ensuring smooth and conflict-free code integration.