Why is the merge tool disabled in Eclipse for a EGit-managed project?

Question

As per the EGit User Guide, to use the merge tool, one should right-click on the resource with a merge conflict and then select Team > Merge Tool

Answer 1

The only time (other than a bug) that the Merge Tool would be disabled is that when you are in any status other than the Conflicts one; i.e. you will only see that option enabled when the status is Conflicts. The status is shown next to the project name in most views, such as Project Explorer and Synchronize.

Make sure you have merged with desired branch, then if your merge results in conflicts, your project will enter Conflicts mode, and the Merge Tool will be enabled.