fix: handle empty context lines in unified diffs

[andyfeller]

Summary

Fix empty context lines being silently dropped by the unified diff parser, which causes hunk line counter desynchronization and can cascade into losing entire hunks and files from parsed output.

Fixes #50

Problem

The schemaContent array defines the context (unchanged) line pattern as /^\s+/, which requires one or more whitespace characters. In the unified diff format, context lines are prefixed with a single space — but when blank context lines have that leading space stripped, they become empty strings ("") that match none of the four content patterns and are silently dropped.

This commonly occurs when:

• Git is configured with diff.suppressBlankEmpty = true
• Diff output is post-processed to strip trailing whitespace

The Cascade

Dropping a context line means the oldLines/newLines counters never reach 0, so the parser stays in content mode. Subsequent @@ hunk headers and diff --git file boundaries are consumed as content instead of triggering transitions — entire hunks and files are lost.

Fix

One-character change in parse.js: /^\s+/ → /^\s*/

This is safe because schemaContent patterns are checked in order:

1. /^\ No newline/ — eof marker
2. /^-/ — deletion
3. /^\+/ — addition
4. /^\s*/ — context line (catch-all for remaining hunk body lines)

Within a correctly-formed hunk body, anything that isn't a deletion, addition, or eof marker can only be a context line.

Tests Added

7 new tests in a "empty context lines (suppressBlankEmpty)" describe block:

Test	What it covers
between del/add	Empty context line between deletion and addition
start of hunk	Empty context line as first line after @@ header
end of hunk	Empty context line as last line in hunk
multiple consecutive	Several empty context lines in a row
second hunk preserved	Cascade: empty line in hunk 1 doesn't lose hunk 2
second file preserved	Cascade: empty line in file 1 doesn't lose file 2
regression guard	Standard context lines with leading space still work

All 30 tests pass (23 existing + 7 new), zero lint errors.

[sergeyt]

wow 😄 . thanks

[andyfeller]

wow 😄 . thanks

Thank you, Sergey! 🙇