tests: Add fuzzy mode tests for interdiff

Add comprehensive test coverage for the fuzzy diffing mode:
- fuzzy1-10: Core fuzzy diffing scenarios including context differences,
  rejected hunks, real-world kernel patches, and edge cases.
- fuzzy11: '\ No newline at end of file' marker handling.
- fuzzy12: Addition at line 1 with zero pre-context.
- fuzzy13: File deletion (--- a/file, +++ /dev/null) handling.
- fuzzy14: Mode-only patches with no diff hunks.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: kerneltoast

Makefile.am

@@ -432,7 +432,21 @@ TESTS = tests/newline1/run-test \
 	tests/git-deleted-file/run-test \
 	tests/git-pure-rename/run-test \
 	tests/git-diff-edge-cases/run-test \
-	tests/malformed-diff-headers/run-test
+	tests/malformed-diff-headers/run-test \
+	tests/fuzzy1/run-test \
+	tests/fuzzy2/run-test \
+	tests/fuzzy3/run-test \
+	tests/fuzzy4/run-test \
+	tests/fuzzy5/run-test \
+	tests/fuzzy6/run-test \
+	tests/fuzzy7/run-test \
+	tests/fuzzy8/run-test \
+	tests/fuzzy9/run-test \
+	tests/fuzzy10/run-test \
+	tests/fuzzy11/run-test \
+	tests/fuzzy12/run-test \
+	tests/fuzzy13/run-test \
+	tests/fuzzy14/run-test
 
 # Scanner tests (only when scanner-patchfilter is enabled)
 if USE_SCANNER_PATCHFILTER

tests/fuzzy1/run-test

@@ -0,0 +1,91 @@
+#!/bin/sh
+
+# This is an interdiff(1) testcase.
+# Test: Fuzzy diffing with one rejected hunk per patched file.
+
+
+. ${top_srcdir-.}/tests/common.sh
+
+cat << 'EOF' > patch1
+--- file
++++ file
+@@ -1,4 +1,4 @@
+-line 1
++LINE 1
+ line 2
+ line 3
+ line 4
+EOF
+
+cat << 'EOF' > patch2
+--- file
++++ file
+@@ -5,9 +5,6 @@
+ line 5
+ if
+ 1
+-fi
+-if
+-2
+ fi
+ A
+ B
+EOF
+
+cat << 'EOF' > expected
+================================================================================
+*    DELTA DIFFERENCES - code changes that differ between the patches          *
+================================================================================
+
+--- file
++++ file
+@@ -1,4 +1,4 @@
+-LINE 1
++line 1
+ line 2
+ line 3
+ line 4
+
+################################################################################
+!    REJECTED PATCH2 HUNKS - could not be compared; manual review needed       !
+################################################################################
+
+--- file
++++ file
+@@ -5,9 +5,6 @@
+ line 5
+ if
+ 1
+-fi
+-if
+-2
+ fi
+ A
+ B
+
+================================================================================
+*    CONTEXT DIFFERENCES - surrounding code differences between the patches    *
+================================================================================
+
+--- file
++++ file
+@@ -1,4 +1,9 @@
+-line 1
+-line 2
+-line 3
+-line 4
++line 5
++if
++1
++fi
++if
++2
++fi
++A
++B
+EOF
+
+${INTERDIFF} --fuzzy patch1 patch2 2>errors >output
+[ -s errors ] && exit 1
+
+cmp output expected || exit 1