I want to compare different revisions of a single file. On the commandline I can do this by
git difftool <revision_1>:<file_1> <revision_2>:<file_2>.
But I want to use a gui to select which revisions are compared. So, the gui should show a list of commits where the specified file is changed and from this list two commits should be selectable which are then passed to the actual difftool.
gitk -p file
Does something similar but it only generates diffs between succeeding commits. (And the output is just conventional diff and not side-by-side difftool).
With the help of this answer I found a solution my self, which does not need additional software:
gitk can be configured to use an external difftool (like kdiff3)
Edit->Preferences->...
Then one uses
gitk -p <file> -> Select revision1 and right-click on revision2 -> "diff selected -> this" -> in the right-hand panel right-click on the file and select "external diff-tool".