External diff tool exiting with code 1 should not cause a warning

[dotdash]

Description

diff uses exit code 0 to signal that there were no changes, 1 to signal that there were changes, and an exit code >1 to signal an error. Tools like delta do the same, but jj treats exit code 1 as a problem.

Steps to Reproduce the Problem

1. Change something in your working copy
2. Run jj diff --config ui.diff.tool=diff or jj diff --config ui.diff.tool=delta

Expected Behavior

No warnings show up.

Actual Behavior

The output ends with:

Warning: Tool exited with exit status: 1 (run with --debug to see the exact invocation)

Specifications

• Platform: Linux Debian Sid
• Version: jj 0.25.0-041c4fecb77434dd6720e7d7f1ce48d9575ac5f7

[yuja]

It's not an error but a warning for that reason. Maybe we can add a per-tool list of expected exit codes to suppress the warning.

fwiw, you might want to set up delta as a pager, not a diff generator.

[bryceberger]

Comment from PR (#5257 (review)):

Perhaps it would be better to reduce complexity in jj by having the user write their own wrapper for the tool? Then it can handle arbitrary exit conditions.

I'm in favor of a wrapper. Minimal example:

#!/usr/bin/env bash
diff "$@"
status=$?
case $status in
0 | 1) ;;
*)
    # custom handling, etc
    exit $status
    ;;
esac

[dotdash]

fwiw, you might want to set up delta as a pager, not a diff generator.

That works for e.g. jj diff but not for jj log -p because delta doesn't recognize the diff format due to the vertical bar left of the diff (it fails the same way with git log --graph -p). Though using ui.diff.tool the output in jj log -p is still broken WRT the file path, because delta gets the raw paths instead of a git style diff 🤔

Should I file a separate issue for that?

[arxanas]

fwiw, you might want to set up delta as a pager, not a diff generator.

That works for e.g. jj diff but not for jj log -p because delta doesn't recognize the diff format due to the vertical bar left of the diff (it fails the same way with git log --graph -p). Though using ui.diff.tool the output in jj log -p is still broken WRT the file path, because delta gets the raw paths instead of a git style diff 🤔

Should I file a separate issue for that?

I don't know if it's relevant, but there's a specific note for configuring delta here, is it applicable? https://jj-vcs.github.io/jj/v0.25.0/config/#processing-contents-to-be-paged