Fix recountdiff bug handling git diffs (#49)

Assisted-by: Cursor

Author: twaugh

Makefile.am

@@ -228,6 +228,7 @@ TESTS = tests/newline1/run-test \
 	tests/recount5/run-test \
 	tests/recount6/run-test \
 	tests/recount7/run-test \
+	tests/recount8/run-test \
 	tests/unwrapdiff1/run-test \
 	tests/overstrip/run-test \
 	tests/context1/run-test \

NEWS

@@ -22,6 +22,12 @@ Patchutils news
 	processing patches with multiple files, breaking the patch format.
 	Addresses GitHub issue #48.
 
+	Fixed recountdiff corruption of new file headers when git signature
+	lines are present. Previously, recountdiff would incorrectly change
+	"@@ -0,0 +1,N @@" to "@@ -1 +1,N @@" for new files in patches containing
+	git signature lines (e.g., "-- \n2.50.1"), causing patch application
+	to fail. Addresses GitHub issue #49.
+
 0.4.2 (stable)
 
 	Build system improvements: only run xmlto once during documentation

scripts/recountdiff.in

@@ -77,6 +77,10 @@ while ($i < $#line) {
 	my $spit = 0;
 	if (/^\s/ or /^$/) { $orig++; $new++; }
 	elsif (/^\+/) { $new++; }
+	elsif (/^-- $/) {
+	    # Git signature line - end of patch content
+	    $spit = 1;
+	}
 	elsif (/^-/) {
 	    # Look out for new file changes.
 	    if (/^--- /) {
@@ -125,17 +129,33 @@ foreach (@off_lines) {
 	next;
     }
     $line[$_] =~ /^@@ -(\d+),?(\d+)? \+(\d+),?(\d+)? @@(.*)$/;
-    ($ooff,$oc,$nc,$misc) = ($1,$2,$4,$5);
-    $oc = 1 unless defined($oc);
+    ($ooff,$oc,$noff_orig,$nc,$misc) = ($1,$2,$3,$4,$5);
+
+    # Check for new file before applying defaults
+    $is_new_file = ($ooff == 0 && defined($oc) && $oc == 0);
+
+    # For new files, preserve oc=0; otherwise apply default
+    if (!$is_new_file) {
+        $oc = 1 unless defined($oc);
+    }
     $nc = 1 unless defined($nc);
-    $noff = $ooff + $offset;
-    $noff++ if ($oc == 0);
-    $noff-- if ($nc == 0);
+
+    # For new files (ooff=0, original oc=0), preserve the original new offset
+    if ($is_new_file) {
+        $noff = $noff_orig + $offset;
+    } else {
+        $noff = $ooff + $offset;
+        # Don't adjust offset for new files (when ooff is 0 and oc is 0)
+        $noff++ if ($oc == 0 && $ooff != 0);
+        $noff-- if ($nc == 0);
+    }
     $line[$_] = "@@ -$ooff";
     $line[$_] .= ",$oc" if ($oc != 1);
     $line[$_] .= " +$noff";
     $line[$_] .= ",$nc" if ($nc != 1);
     $line[$_] .= " @@" . "$misc\n";
+
+
     $offset += $nc - $oc;
 }
 

tests/recount8/run-test

@@ -0,0 +1,37 @@
+#!/bin/sh
+
+# This is a recountdiff(1) testcase.
+# Test: Fix bug with new files when git signature lines are present (issue #49).
+
+. ${top_srcdir-.}/tests/common.sh
+
+cat <<"EOF" > patch
+diff --git a/test_file b/test_file
+new file mode 100644
+index 0000000..83db48f
+--- /dev/null
++++ b/test_file
+@@ -0,0 +1,3 @@
++line1
++line2
++line3
+-- 
+2.50.1
+
+EOF
+
+${RECOUNTDIFF} patch > patch-recounted || exit 1
+cat <<"EOF" | cmp - patch-recounted || exit 1
+diff --git a/test_file b/test_file
+new file mode 100644
+index 0000000..83db48f
+--- /dev/null
++++ b/test_file
+@@ -0,0 +1,3 @@
++line1
++line2
++line3
+-- 
+2.50.1
+
+EOF