org-email-link-description-format (Was: Re: org-store/insert-link truncating the full subject of mails)

["Garreau\, Alexandre" <galex-713@galex-713.eu>]

On 2018-10-28 at 10:05, Amin Bandali wrote:
> That said, I still find the default a bit obtuse and frankly
> unexpected.  I don’t know, maybe a nice middle ground between the
> current behaviour and completely removing the limit would be to
> increase the limit from 30 to 78 characters, the recommended
> maximum number of characters in a line according to RFC 2822 [0].
> That somehow feels less arbitrary, and would cover a larger
> portion of subjects.
>
> [0]: https://tools.ietf.org/html/rfc2822#section-2.1.1

Okay, so I did not read carefully enough: this is a per line limit,
however Gnus already include this limitation in fill-column so that to
fold subject line in several lines that will be no more than 78
characters, there’s no need to limit to 78 characters, and indeed I
sometimes end with subject lines of more than one line, and wouldn’t
like to see my normal subject line truncated.  The same way, org-mode
will naturally see its paragraphs filled if wanted by the user (otherise
there are no problems in long lines, except, afaik, by default, it
disable truncating lines).

On 2018-10-28 at 18:01, Garreau, Alexandre wrote:
> Rather cutting it, I’d rather try to find the gnus function that cut
> subject lines so it does more semantically (like, removing the entire
> Was: part if it doesn’t fit, rather than cutting it in the middle), but
> 78 seems totally more reasonable, at worse, indeed: but maybe that
> aforementioned gnus function does something related to it (maybe it does
> cut when it exceed 78 chars?)?
>
> However I was unable to find it by el-searching for "was:?", so I’ll ask
> them directly, hoping they know and answer.

So the function I was searching is `message-strip-subject-trailing-was',
and only strip the was part, it doesn’t conditionally strip “Was” if
there were several, or if the subject line was too long.  Yet it can be
used for org-mode as the “Was:” trailing part is likely not to be
interesting at all for refering to a particular message, as anyway it
will be found again when visiting the said article.

What’s more interesting is it’s used in a function
`message-simplify-subject', calling a customizable list of functions
(`message-simplify-subject-functions'), that will simplify deeply the
subject, removing also the “Re:”, the mailing-list part, encoded parts,
etc.  Yet, as it currently only used for replying, it seems to, wrongly
imo, add a “Re:” to the subject line (while this should be its scope,
imo).  So this one is not usable as is.

But `message-strip-subject-re' might be used per se itself, otherwise,
as it seems to me the “Re:” might not be interesting as well, though
mailing-list part may be useful, as in
`org-email-link-description-format' there is nothing to refer to the
group (either the group name in gnus, or either content of “Newsgroups”
header or mailing-list (content of “List-id” or “List-post”, either
address or human-readable part)), but not all mailing-list embed one, so
it might bring inconsistency, and adding a said new format-specifier to
`org-email-link-description-format' seems to me preferable (why not “%g”
for “group”?).

So may I suggest to change `org-email-link-description' and update
`org-email-link-description-format', so that to support a "%g"
specifier, to refer to the content of :group (or should we add something
to refer List-ID/List-Post?), and a %S that’d return the subject,
simplified by `message-strip-subject-trailing-was',
`message-strip-subject-trailing-re', or, maybe rather, by all the
functions inside `message-simplify-subject-functions' (waiting for
`message-simplify-subject' to be corrected).