GeezerVison

In a unified diff, a range with a count of 0 names the line before it: diff -U0 and git diff -U0 write 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:

The parsers already treat -0,0 this 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,0 for 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,0 or +N,0 range (N > 0) will now be read one line later.

Tests are added next to testNewFileCreation in GenerateUnifiedDiffTest, next to testWriteWithNewFile in UnifiedDiffWriterTest, and in UnifiedDiffReaderTest; they fail on master. mvn -B package passes 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 GNU diff and patch.

Written with AI assistance (Claude); I have reviewed the change.