bug#56442: gnus-search-run-search: Hits notmuch command line length limits

[Sean Whitton]

Hello,

I'm running a pretty innocent notmuch query over a fairly small Maildir:

"((List:debian-devel.lists.debian.org) or ... or
(List:debian-haskell.lists.debian.org) or
(List:debconf-discuss.lists.debian.org)) and (not path:annex/**)"

but gnus-search-run-search fails to return any results.  The reason is
that Gnus first runs the query with --output=threads to obtain a list of
thread ids, and then runs another query with --output=files and a query
constructed from the output of the first query: "thread:000000000000d9d0
or thread:000000000000d9e0 or thread:000000000000d268 or ..."

The resulting command fails completely:

    emacs: /usr/bin/notmuch: Argument list too long

Instead of running two searches like this, we can just surround the
whole query like this: "thread:{QUERY}".  The manual says it's exactly
equivalent:

    ... the user should think of the query thread:{<something>} as
    expanding to all of the thread IDs which match <something>; not‐
    much then performs a second search using the expanded query.

This should be faster, too, with only running a single external command.
Here is the patch I'm thinking I'll apply, if anyone has comments.

-- 
Sean Whitton

0001-Use-notmuch-thread-operator-instead-of-performing-tw.patch
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