Diffs
You can use the editor to see a diff between two or more files. For example, to compare foo1.txt with foo2.txt start Vem in your terminal with:
vem -d foo1.txt foo2.txt
The files will be shown side-by-side as in the example:
The diff highlighting in the example is pretty straightforward:
The green section means that the code is present in one file but not in the other.
The blue section means that the code is present in both files but with modifications.
Folds are used to hide large sections of common code so you have a better overview of the differences between the files. You can toggle a fold open and close with b a (for more info about folds, check the Folds section).
The diff will be updated automatically as you change the files: the editor will detect the changes and update the view accordingly. However, you can also force the diff to be updated manually:
:diffupdate
This may be useful if the diff gets out of sync because of a complex operation.
You can also start a diff between two or more windows of a tabpage, by executing:
:diffthis
in each window you want to diff. If you want to start a diff between all the windows of a tabpage you can do:
:windo diffthis
and window will take care of executing diffthis in every window.
To stop the diff, execute:
:windo diffoff
Vem as Git mergetool
You can use Vem as the tool to solve Git conflicts. To do so, add the following lines to either ~/.gitconfig, if you want the change to be global to your user, or .git/config inside a repository, if you only want that repository to be affected:
[merge]
tool = vem
[mergetool "vem"]
cmd = vem -f -d -c '4wincmd w | wincmd J' \"$LOCAL\" \"$BASE\" \"$REMOTE\" \"$MERGED\"
prompt = false
These lines will make Git to start Vem showing a 3-way diff for each file in conflict when you execute git mergetool:
The windows of the diff contain the following information:
+--------------------------------+ | LOCAL | BASE | REMOTE | +--------------------------------+ | MERGED | +--------------------------------+
LOCAL: shows a temporary file with your changes.
REMOTE: shows a temporary file with the changes that you're trying to merge in.
BASE: shows a temporary file with the common ancestor to both LOCAL and REMOTE.
MERGED: shows the actual buffer where you have to fix the conflict. (Modifiying the other files has no effect).
Once the conflict has been resolved in the MERGED window, save its content and exit Vem. Git will then open Vem again for the next conflicting file. When there are no more conflicts left, then you'll be ready to commit the fixes.
Git difftool
Finally, it is also possible to use Vem as Git difftool by adding the following lines to Git's configuration:
[diff]
tool = vem
[difftool]
prompt = false
[difftool "vem"]
cmd = vem -f -d -c 'wincmd l' \"$LOCAL\" \"$REMOTE\"
You can use git difftool to see the changes in your working copy inside Vem.