Show the difference of lines between two files

Question

How to implement a functionality in emacs to show the difference of contents between two files opened in two buffers? Kind of like revdiff when using mercurial.

Answer 1

Emacs has ediff, which can diff two files. To use it, just do M-x ediff, and specify the two files you want to diff.

Answer 2

BTW, if you want to see the differences between two blocks of text in the same buffer, you can do it as follows: - make sure smerge-mode is loaded (e.g. M-x load-library RET smerge-mode RET). - go to the beginning of the first bloc, C-SPC - go the beginning of the second bloc, C-SPC - go to the end of the second bloc, M-x smerge-makeup-conflict RET - then you can use C-c ^ R or C-c ^ = to view the differences. Note that this works better if the two blocs are pretty much consecutive.