jj split always includes new files (when using scm-diff-editor)

[chriskrycho]

Description

When adding a new file, I cannot get jj split to not include a newly-added file, regardless of whether it is included in the "diff".

Note: see discussion; this is not strictly a jj issue, but primarily a function of how diff editing tools handle what jj split needs. Workarounds/solutions:

• Add the file in the first commit and everything else later, then jj move or jj rebase as makes sense.
• Use a diff editor (including the default, Meld) which allows you to delete the file from the right-hand-side of the merge. scm-diff-editor and ksdiff both struggle here, but other tools get it right.

Steps to Reproduce the Problem

1. echo "a" > a.txt
2. jj commit -m "add a"
3. echo "b" >> a.txt && echo "b" > b.txt
4. jj split
5. Only include a.txt in the first commit (and include all of it).

Expected Behavior

b.txt should not be present in the first commit, so this should now show the commit message editor for the first commit.

Actual Behavior

b.txt is present in the first commit, so the result is "Nothing changed".

Specifications

• Platform: macOS 13.4.1 (c)
• Version: 0.8.0

[martinvonz]

I think this is arxanas/git-branchless#995.

[chriskrycho]

Ah, I see. Because of the way the flow works, you have to be able to delete the file. (Kaleidoscope also struggled with this, but Meld seems to handle it fine.) Feels adjacent to #1905. Closing as not a jj issue exactly, but hopefully the existence of the issue here will help other folks.

[ilyagr]

Workaround by @martinvonz from https://discord.com/channels/968932220549103686/969829516539228222/1135299839706529852:

You can work around it by passing the paths you want in the first commit to the command