Viewing changes to deleted files in git

Question

Let's say that when I branch off from master, there's a file colors.txt on the master branch of my repo with these contents:

red
green
blue
yellow

I then branch off into my-branch, in which I make the following changes:

1. Delete colors.txt

2. Add red.txt with these contents:

   red
   

3. Add green.txt with these contents:

   green
   

4. Add blue.txt with these contents:

   blue
   

5. Add yellow.txt with these contents:

   yellow
   

Now, there have been some changes on master that I need, so I want to merge. However, someone has also changed colors.txt to:

red
green
blue
yellow
orange
purple

During my merge, the only information I get is that I deleted the file colors.txt, so how can I see the changes that have been to the file on master so I can appropriately resolve the conflict (in this case, by adding the files orange.txt and purple.txt)?

Answer 1

You can show all changes done to that file on master using this command:

git diff HEAD...master -- colors.txt

This should lead to this output in your case:

red
green
blue
yellow
+orange
+purple

Using three dots for git diff will show the changes of all commits which are parents of the second referenced commit but not of the first referenced commit. Therefore, using this you will see all changes which would be merged if the file had not been deleted.

By using -- colors.txt the changes shown by git diff are limited to that file.

A more generic version of that command would be

git diff HEAD...MERGE_HEAD -- colors.txt

MERGE_HEAD is always set to the merged commit, thus it can replace the merged branch name. Using this you could even set up an alias to reuse this command:

git config --global alias.merge-diff-theirs "diff HEAD...MERGE_HEAD"

Afterwards you can just do

git merge-diff-theirs -- colors.txt