FA-75719 / Text diff and three-way merge / Member archive

Patch reversal: reversed blocks list additions before removals · case 04

The reversed hunk shows new lines before old lines inside each change.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Reverse one unified hunk: swap the old and new ranges in the header, keeping each range's count omitted if it was omitted and keeping any trailing header text; swap "-" and "+" on body lines; within each run of changed lines emit the (new) removed lines before the (new) added lines; a "\" marker line stays attached to the line it follows.

Why this case matters

Reverting a change applies the reversed patch, which must still be a valid, conventionally ordered hunk.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
replacement block	`["@@ -3,2 +3,2 @@ def f():", " a", "+b", "-B", " c"]`	`["@@ -3,2 +3,2 @@ def f():", " a", "-B", "+b", " c"]`	Failed

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