On Sat, Nov 03 2018, Jeff Templon wrote:
> No new mail. Removed 577 messages. Detected 89 file renames.
>
> 577 + 89 = 666 ... my guess is that there were 577 messages and 89 files
> that represented duplicates of messages.

Yes. Among the messages you had tagged as deleted you had 577 unique
message IDs. In addition, you had another 89 files with message IDs that
were duplicates of one of the 577.

> But I didn't rename the files, I deleted them.  Should I worry?

Nope. Nothing to worry about here.

> Why is the message inaccurate?

Because notmuch has a more narrow view of what a "rename" is than you
do.

A file rename is a high-level operation that will be seen by notmuch as
multiple operations seen over the course of a single run of notmuch
new:

  1. A new file is added with a message ID that already exists in the
     database

  2. A file is removed with a message ID for which there are multiple
     files in the database

But notmuch doesn't detect whether both of these operations are seen in
a single pass in order to detect a rename. Instead, what it is doing is
counting every occurence of (2) above as a rename. Here's what the code
looks like (notmuch-new.c:remove_filename):

    status = notmuch_database_remove_message (notmuch, path);
    if (status == NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID) {
	add_files_state->renamed_messages++;
	if (add_files_state->synchronize_flags == true)
	    notmuch_message_maildir_flags_to_tags (message);
	status = NOTMUCH_STATUS_SUCCESS;
    } else if (status == NOTMUCH_STATUS_SUCCESS) {
	add_files_state->removed_messages++;
    }

So, whenever removing a filename, it will either get counted as a rename
(if there is still at least one other filename in the database with the
same message ID), or it will get counted as a removal (if this was the
last filename for message ID).

I suppose you could come up with some other name for what it is
counting, such as "removals of duplicate messages" instead of "rename",
but that's what's happening.

I hope that helps.

-Carl