Fix grepdiff --status by passing status as pointer

The grepdiff --status flag was not working correctly, particularly
with --empty-files-as-absent. The issue was that status needed to
be updated after empty file processing but before filename display.

This commit refactors the code to pass status by pointer to the
diff processing functions (do_unified, do_context, do_git_diff_no_hunks),
allowing them to update the status value at the correct time.

Changes:
- Modified function signatures to accept char *status instead of char status
- Added status update logic after empty file processing in each function
- Updated all callers to pass &status instead of status
- Removed duplicate status update logic that was previously done after
  the functions returned

This ensures grepdiff -s displays the correct status (+/-/!) for all
file types, including:
- New files (show +)
- Deleted files (show -)
- Modified files (show !)
- Empty files when --empty-files-as-absent is used

All 187 tests pass.

Assisted-by: Claude Code

Author: twaugh

src/filterdiff.c

@@ -359,7 +359,7 @@ static int
 do_git_diff_no_hunks (FILE *f, char **header, unsigned int num_headers,
 		      int match, char **line, size_t *linelen,
 		      unsigned long *linenum, unsigned long start_linenum,
-		      char status, const char *bestname, const char *patchname,
+		      char *status, const char *bestname, const char *patchname,
 		      int *orig_file_exists, int *new_file_exists,
 		      enum git_diff_type git_type)
 {
@@ -386,6 +386,16 @@ do_git_diff_no_hunks (FILE *f, char **header, unsigned int num_headers,
 		break;
 	}
 
+	/* Update status based on file existence (do this early so returns below have correct status) */
+	if (status != NULL && mode != mode_filter && show_status &&
+	    orig_file_exists != NULL && new_file_exists != NULL) {
+		if (!*orig_file_exists)
+			*status = '+';
+		else if (!*new_file_exists)
+			*status = '-';
+		/* else: keep existing '!' value for modifications */
+	}
+
 	/* If this diff matches the filter, display it */
 	if (match) {
 		if (mode == mode_filter) {
@@ -394,7 +404,7 @@ do_git_diff_no_hunks (FILE *f, char **header, unsigned int num_headers,
 				fputs (header[i], stdout);
 		} else if (mode == mode_list && !displayed_filename) {
 			if (!show_status) {
-				display_filename (start_linenum, status,
+				display_filename (start_linenum, *status,
 						  bestname, patchname);
 			}
 			displayed_filename = 1;
@@ -455,7 +465,7 @@ static int
 do_unified (FILE *f, char **header, unsigned int num_headers,
 	    int match, char **line,
 	    size_t *linelen, unsigned long *linenum,
-	    unsigned long start_linenum, char status,
+	    unsigned long start_linenum, char *status,
 	    const char *bestname, const char *patchname,
 	    int *orig_file_exists, int *new_file_exists)
 {
@@ -671,7 +681,7 @@ do_unified (FILE *f, char **header, unsigned int num_headers,
 				if (!displayed_filename) {
 					displayed_filename = 1;
 					display_filename (start_linenum,
-							  status, bestname,
+							  *status, bestname,
 							  patchname);
 				}
 
@@ -746,14 +756,24 @@ do_unified (FILE *f, char **header, unsigned int num_headers,
 			*new_file_exists = 0;
 	}
 
+	/* Update status based on final file existence after empty file processing */
+	if (status != NULL && mode != mode_filter && show_status &&
+	    orig_file_exists != NULL && new_file_exists != NULL) {
+		if (!*orig_file_exists)
+			*status = '+';
+		else if (!*new_file_exists)
+			*status = '-';
+		/* else: keep existing '!' value for modifications */
+	}
+
 	return ret;
 }
 
 static int
 do_context (FILE *f, char **header, unsigned int num_headers,
 	    int match, char **line,
 	    size_t *linelen, unsigned long *linenum,
-	    unsigned long start_linenum, char status,
+	    unsigned long start_linenum, char *status,
 	    const char *bestname, const char *patchname,
 	    int *orig_file_exists, int *new_file_exists)
 {
@@ -1020,7 +1040,7 @@ do_context (FILE *f, char **header, unsigned int num_headers,
 					if (!displayed_filename) {
 						displayed_filename = 1;
 						display_filename(start_linenum,
-								 status,
+								 *status,
 								 bestname,
 								 patchname);
 					}
@@ -1150,6 +1170,16 @@ do_context (FILE *f, char **header, unsigned int num_headers,
 			*new_file_exists = 0;
 	}
 
+	/* Update status based on final file existence after empty file processing */
+	if (status != NULL && mode != mode_filter && show_status &&
+	    orig_file_exists != NULL && new_file_exists != NULL) {
+		if (!*orig_file_exists)
+			*status = '+';
+		else if (!*new_file_exists)
+			*status = '-';
+		/* else: keep existing '!' value for modifications */
+	}
+
 	return ret;
 }
 
@@ -1180,7 +1210,7 @@ static int filterdiff (FILE *f, const char *patchname)
 		int (*do_diff) (FILE *, char **, unsigned int,
 				int, char **, size_t *,
 				unsigned long *, unsigned long,
-				char, const char *, const char *,
+				char *, const char *, const char *,
 				int *, int *);
 
 		orig_file_exists = 0; // shut gcc up
@@ -1375,19 +1405,13 @@ static int filterdiff (FILE *f, const char *patchname)
 								/* Process the git diff (it will handle filename display) */
 				result = do_git_diff_no_hunks (f, header, num_headers,
 							     match, &line, &linelen, &linenum,
-							     start_linenum, status, p, patchname,
+							     start_linenum, &status, p, patchname,
 							     &orig_file_exists, &new_file_exists,
 							     git_type);
 
 				/* Print filename with status if in list mode and matches */
-				if (match && show_status && mode == mode_list) {
-					if (!orig_file_exists)
-						status = '+';
-					else if (!new_file_exists)
-						status = '-';
-
+				if (match && show_status && mode == mode_list)
 					display_filename (start_linenum, status, p, patchname);
-				}
 
 				/* Clean up */
 				free (git_old_name);
@@ -1476,19 +1500,13 @@ static int filterdiff (FILE *f, const char *patchname)
 		result = do_diff (f, header, num_headers,
 				  match, &line,
 				  &linelen, &linenum,
-				  start_linenum, status, p, patchname,
+				  start_linenum, &status, p, patchname,
 				  &orig_file_exists, &new_file_exists);
 
 		// print if it matches.
-		if (match && show_status && mode == mode_list) {
-			if (!orig_file_exists)
-				status = '+';
-			else if (!new_file_exists)
-				status = '-';
-
+		if (match && show_status && mode == mode_list)
 			display_filename (start_linenum, status,
 					  p, patchname);
-		}
 
 		switch (result) {
 		case EOF: