What to do if git-am fails with “does not exist in index”?

Question

I have a patch that gives out the following output when I try to apply it with git am

Checking patch old/filename... error: old/filename: does not exist in index 

Within the patch old/filename is actually moved to new/filename but it seems the original file is already missing from the source tree.

So what is the error about and how to solve / work-around it? Can it just be ignored (with --reject or so)?

Answer 1

The patch was not created against the correct source tree.

One way this could happen:

Assume your original branch (the one you want to apply the patch to) has commits:

1. 1a -> 1b -> 1c -> 1d

This branch is then cloned, and new commits are made:

2. 1a -> 1b -> 1c -> 1d -> 1e

Commit 1e included old/filename

Now you do the work in the patch, based on the second branch, not the original one:

3. 1a -> 1b -> 1c -> 1d -> 1e -> 1f

Commit 1f included the rename old/filename -> new/filename

Now, if you create a patch for commit 1f, you won't be able to apply it on top of commit 1d, because commit 1e is missing where old/filename was added to the index/repository.