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

It can depend on the version of EGit you are using, and on the operation that lead to the conflict.
See for instance bug 339092 which mention merge tool being not enabled in the case of a conflict after cherry-picking: only the just released EGit 0.12 would support that.