You can do this by sending an HTTP post to Tvheadend with the original location of the file, and its new path:
http[s]://[user[:pass]@]1.2.3.4:5678/api/dvr/entry/filemoved?src=sourcefile.ts&dst=newfile.ts
user
and
pass
are optional, depending upon your user/access restrictions in Tvheadend,
1.2.3.4
is the IP address of your Tvheadend server,
5678
is the HTTP (not HTSP) port for your server (9981, by default),
sourcefile.ts
is the URL-encoded absolute path of the original location of the file, and
newfile.ts
is the URL-encoded absolute path to the new location of the file.
If you want to script it, you can use @curl@, which works out well. Just ensure that you properly URL-encode the parameters, as malformed POSTs to Tvheadend tend to crash the server. (I know, as I've forgotten to do so on several occasions.)