Hi,

In debhelper/13.26, `dh_assistant list-guessed-dh-config-files` will now
report `debhelper` commands that does not declare which config files it
supports. As an example:

```shell
$ dh_assistant list-guessed-dh-config-files
{
    "commands-not-introspectable": [
       "dh_autoreconf",
       "dh_strip_nondeterminism"
    ],
    # ... more JSON here, omitted for brevity
}
```

This is in turn used by `debputy migrate-from-dh` to warn people when
`debhelper` config files might be overlooked.

In case of `dh-autoreconf`, there are two helpers.

  * `dh_autoreconf`: Not introspectable currently.
  * `dh_autoreconf_clean`: Introspectable (NOOP promise)

I believe this bug can be fixed by adding the following comment anywhere
in the `dh_autoreconf` command (the file found PATH - imports are not
followed):

```
# INTROSPECTABLE: CONFIG-FILES path(debian/autoreconf)
```

My argument here is that:

  1) The helper can never be skipped (so NOOP promise is not valid)
  2) The helper reacts to `debian/autoreconf` if present.

If either of these are false, then please review `doc/PROGRAMMING.md` in
debhelper/13.26 for alternatives or reply back to me for assistance.

Best regards,
Niels

PS: The NOOP promise also accepts the `path(...)` from
`debhelper/13.26`. In theory, `dh_autoreconf_clean` could now use
`path(debian/autoreconf.before) path(debian/autoreconf.after)` in its
NOOP promise. However, since `debhelper/13.25` and older does not
understand that hint, it is probably best to leave the current hint
as-is despite being a bit too overreaching.