convert: update subprocess_read_status() to not die on EOF

Enable sub-processes to gracefully handle when the process dies by
updating subprocess_read_status to return an error on EOF instead of
dying.

Update apply_multi_file_filter to take advantage of the revised
subprocess_read_status.

Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: benpeart

convert.c

@@ -635,7 +635,10 @@ static int apply_multi_file_filter(const char *path, const char *src, size_t len
 	if (err)
 		goto done;
 
-	subprocess_read_status(process->out, &filter_status);
+	err = subprocess_read_status(process->out, &filter_status);
+	if (err)
+		goto done;
+
 	err = strcmp(filter_status.buf, "success");
 	if (err)
 		goto done;
@@ -644,7 +647,10 @@ static int apply_multi_file_filter(const char *path, const char *src, size_t len
 	if (err)
 		goto done;
 
-	subprocess_read_status(process->out, &filter_status);
+	err = subprocess_read_status(process->out, &filter_status);
+	if (err)
+		goto done;
+
 	err = strcmp(filter_status.buf, "success");
 
 done:

sub-process.c

@@ -21,13 +21,15 @@ struct subprocess_entry *subprocess_find_entry(struct hashmap *hashmap, const ch
 	return hashmap_get(hashmap, &key, NULL);
 }
 
-void subprocess_read_status(int fd, struct strbuf *status)
+int subprocess_read_status(int fd, struct strbuf *status)
 {
 	struct strbuf **pair;
 	char *line;
+	int len;
+
 	for (;;) {
-		line = packet_read_line(fd, NULL);
-		if (!line)
+		len = packet_read_line_gently(fd, NULL, &line);
+		if ((len < 0) || !line)
 			break;
 		pair = strbuf_split_str(line, '=', 2);
 		if (pair[0] && pair[0]->len && pair[1]) {
@@ -39,6 +41,8 @@ void subprocess_read_status(int fd, struct strbuf *status)
 		}
 		strbuf_list_free(pair);
 	}
+
+	return (len < 0) ? len : 0;
 }
 
 void subprocess_stop(struct hashmap *hashmap, struct subprocess_entry *entry)

sub-process.h

@@ -44,6 +44,6 @@ static inline struct child_process *subprocess_get_child_process(
  * key/value pairs and return the value from the last "status" packet
  */
 
-void subprocess_read_status(int fd, struct strbuf *status);
+int subprocess_read_status(int fd, struct strbuf *status);
 
 #endif