+static const char *derive_filename(const char *pack_name, const char *suffix,
+ struct strbuf *buf)
+{
+ size_t len;
+ if (!strip_suffix(pack_name, ".pack", &len))
+ die(_("packfile name '%s' does not end with '.pack'"),
+ pack_name);
+ strbuf_add(buf, pack_name, len);
+ strbuf_addch(buf, '.');
+ strbuf_addstr(buf, suffix);
+ return buf->buf;
+}
+
+static void write_special_file(const char *suffix, const char *msg,
+ const char *pack_name, const unsigned char *hash,
+ const char **report)
+{
+ struct strbuf name_buf = STRBUF_INIT;
+ const char *filename;
+ int fd;
+ int msg_len = strlen(msg);
+
+ if (pack_name)
+ filename = derive_filename(pack_name, suffix, &name_buf);
+ else
+ filename = odb_pack_name(&name_buf, hash, suffix);
+
+ fd = odb_pack_keep(filename);
+ if (fd < 0) {
+ if (errno != EEXIST)
+ die_errno(_("cannot write %s file '%s'"),
+ suffix, filename);
+ } else {
+ if (msg_len > 0) {
+ write_or_die(fd, msg, msg_len);
+ write_or_die(fd, "\n", 1);
+ }
+ if (close(fd) != 0)
+ die_errno(_("cannot close written %s file '%s'"),
+ suffix, filename);
+ if (report)
+ *report = suffix;
+ }
+ strbuf_release(&name_buf);
+}
+