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In a unified diff a range with a count of 0 names the line before it, so "@@ -2,0 +3 @@" inserts after line 2. Both parsers took the start as the first affected line and both writers wrote it that way, so a zero-context diff from GNU diff or git was applied one line early, and GNU patch applied ours one line late.
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In a unified diff, a range with a count of 0 names the line before it:
diff -U0andgit diff -U0write an insertion after line 2 as@@ -2,0 +3 @@. java-diff-utils reads and writes that start as the first affected line instead. Its own round trip agrees with itself, but patches exchanged with other tools land one line off:a,b,c->a,b,X,c:diff -U0output parsed byUnifiedDiffUtils.parseUnifiedDiff+applyTo[a, X, b, c][a, b, X, c]UnifiedDiffReader.parseUnifiedDiff[a, X, b, c][a, b, X, c]generateUnifiedDiff(..., 0)header@@ -3,0 +3,1 @@@@ -2,0 +3,1 @@patcha,b,c,Xa,b,X,cThe parsers already treat
-0,0this way (if (old_ln == 0) old_ln = 1), and the writers already emit@@ -0,0 +1,n @@for a new file; this extends the same rule to-N,0for N > 0. Diffs with context of 1 or more only have an empty range when a file is empty, so they are unaffected otherwise.Compatibility: zero-context patches generated by earlier versions of this library with a
-N,0or+N,0range (N > 0) will now be read one line later.Tests are added next to
testNewFileCreationinGenerateUnifiedDiffTest, next totestWriteWithNewFileinUnifiedDiffWriterTest, and inUnifiedDiffReaderTest; they fail on master.mvn -B packagepasses on JDK 8 (154 tests); an earlier run also passed on JDK 11 and for the core module on JDK 17. I also checked the table above against GNUdiffandpatch.Written with AI assistance (Claude); I have reviewed the change.