Try as I might, I have not found any way to launch a three-way comparison with EGit. The synchronize view seems to do it, but It seems to me that the "ancestor" of this comparison is always the "remote" side, which means that "synchronize workspace" will never detect any conflicts, even if there are some.
right-click > compare with > branch, tag... also does a two way comparison : left being the local version, right the other branch's... but no common ancestor is taken into account, thus no conflict detection there either.
Is there any reason for this choice? Is this something that is meant to evolve later on? Or is there something I've missed ?
I think you are right: There seems to be a bug in the synchronize view and a missing feature for the other compare views. Do you want to open bugs for that? I haven't found any.
It should be quite straightforward using JGit to determine the common ancestor of two commits and to use it in the Eclipse compare view.
When comparing a file against another commit or branch, the content of the common ancestor can now be shown using the Show Ancestor Pane button in the compare editor. This will show a third text field showing the content of the ancestor.
Thanks for the follow-up, and sorry for my lack of reaction : I had started investigating about a number of things and forgot to check up on this thread :s. Thanks for taking the time to answer regardless .
I had also raised bug 393294 during my investigations regarding the three way comparisons, as the compare panes are not currently reporting the accurate revision info.