reflogs: fix behaviour around reflogs with newlines - #5275

typedef enum git_reflog_component {
	git_reflog_component_init, // init entry.
	git_reflog_component_oid_old, // length > 0 && length <= OIDSIZE (20) && is_hex(character)
	git_reflog_component_oid_cur, // length > 0 && length <= OIDSIZE (20) && is_hex(character)
	git_reflog_component_commiter, // length > 0 && contains(name) && contains(email) && contains(time)
	git_reflog_component_msg, // length >= 0 && last_at_('\n')
	git_reflog_component_finalize, // finalize. Put entry into array.
} git_reflog_component;

typedef enum parsing_step {
	init,
	oid_old,
	oid_cur,
	commiter,
	msg,
	finalize,
};

component = git_reflog_component_init;

while(buf_size > GIT_REFLOG_SIZE_MIN) {
  switch (component) {
    case git_reflog_component_init: {
      entry = git__calloc(1, sizeof(git_reflog_entry));
      GIT_ERROR_CHECK_ALLOC(entry);

      entry->committer = git__calloc(1, sizeof(git_signature));
      GIT_ERROR_CHECK_ALLOC(entry->committer);
      component = git_reflog_component_oid_old;
      break;
    }
    case git_reflog_component_oid_old: {
      if (git_oid_fromstrn(&entry->oid_old, buf, GIT_OID_HEXSZ) < 0) {
        // error occurred.
        // we should reset cycle.
        // and also we don't need to change component.
        // cleanup.
        invalid_character_position = git_oid_find_invalid_charater_position_at_strn(buf, GIT_OID_HEXSZ);
        if (invalid_character_position < 0) { // error occurred, so, cleanup and leave.
          error_occurred = -1;
        }
        else { // invalid character, seek to position following invalid character and try to get oid again.
          git_reflog_entry__free(entry);
          valid_character_position = 1 + invalid_character_position;
          seek_forward_new(valid_character_position);
          component = git_reflog_component_init;
        }
      }
      else {
        seek_forward_new(GIT_OID_HEXSZ + 1);
        component = git_reflog_component_oid_cur;
      }
      break;
    }
    case git_reflog_component_oid_cur: {
      if (git_oid_fromstrn(&entry->oid_cur, buf, GIT_OID_HEXSZ) < 0) {
        error_occurred = -1;
      }
      else {
        seek_forward_new(GIT_OID_HEXSZ + 1);
        component = git_reflog_component_commiter;
      }
      break;
    }
    case git_reflog_component_commiter: {
      ptr = buf;
      /* Seek forward to the end of the signature. */
      while (*buf && *buf != '\t' && *buf != '\n')
        seek_forward_new(1);
      if (git_signature__parse(entry->committer, &ptr, buf + 1, NULL, *buf) < 0) {
        error_occurred = -1;
      }
      else {
        component = git_reflog_component_msg;
      }
      break;
    }
    case git_reflog_component_msg: {
      if (*buf == '\t') {
        /* We got a message. Read everything till we reach LF. */
        seek_forward_new(1);
        ptr = buf;

        while (*buf && *buf != '\n') seek_forward_new(1);

        entry->msg = git__strndup(ptr, buf - ptr);
        GIT_ERROR_CHECK_ALLOC(entry->msg);
      } else
        entry->msg = NULL;
      while (*buf && *buf == '\n' && buf_size > 1) seek_forward_new(1);
      component = git_reflog_component_finalize;
      break;
    }
    case git_reflog_component_finalize: {
      if (git_vector_insert(&log->entries, entry) < 0) {
        error_occurred = -1;
      }
      else {
        component = git_reflog_component_init;
      }
      break;
    }
  }
  if (error_occurred < 0) {
    break;
  }
}