Re: co-authoring commits

From: Jakub Narębski <jnareb@gmail.com>
Date: Jun 19, 2015, 18:02 UTC
Message-ID: <5584593A.5010406@gmail.com>
In-Reply-To: <20150619042519.GB26001@peff.net>

On 2015-06-19 at 06:25, Jeff King wrote:

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> On Thu, Jun 18, 2015 at 11:25:44PM +0200, Jakub Narębski wrote:
>> Author and committer include datetime in the contents of the
>> field, which is used by Git for heuristics limiting walk. Coauthor
>> would have the same date as author, isn't it? If, after long
>> and involved discussion, we didn't add 'generation' field (for
>> easier cutting history walking), what chance adding 'coauthor'
>> has.
> I don't think the two situations are comparable. I would (and did) argue
> that a "generation" field is a bad header to bake in because of what it
> means (it is redundant with the graph structure).
>
> Whereas "co-author" is not a fundamentally bad; it's just not something
> we chose to support early on, and it would have to be added now.

It is true that "generation" field is redundant with the graph structure, but it is not necessarily something bad. You don't avoid using red-black trees or AVL trees because they keep some _redundant_ "bookkeeping" data in the node structure. Same for "generation" header: it is bookkeeping, but would make Git more effective (faster).

Though I don't think any distributed version control system store such data in their equivalent of commit objects... maybe Veracity (I didn't check)...

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>> OTOH it would be nice to have support for .mailmap, and for
>> grepping... but the former could conceivably be added to the trailer
>> tool, the latter can be done with appropriate regexp in
>> "git log --grep=...".
> I don't think we munge trailers during "git log" pretty-printing at all
> now, but it is certainly something we could add (including mailmap-ing
> them).  That doesn't seem like much more work than showing the co-author
> field, and it's a lot more generally applicable (you could mailmap
> S-O-B, Reviewed-by, and so forth).

This is certainly something nice to have. Though for author and committer (and also for tagger if I remember it correctly) we have mailmap-aware and not-mailmapped versions. There isn't anything like that for trailers.

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>
> Similarly, something like "git shortlog" would have to learn about
> multiple authors under the "co-author" scheme. But likewise, it would
> not be much more work to teach it something like:
>
>   git shortlog --field=Reviewed-by
>
> to handle an arbitrary trailer. And that is much more flexible.

It would also be nice to have something like this for blame... but at least multiple authors support doesn't make much sense wrt display uless using graphical blame tool (like "git gui blame").

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>
>> I wonder what would break if one used 'Name <e@mai.l>, Name <em@i.l>'
>> as the author...
> The "normal" parser we use for pretty-printing goes left-to-right and
> will stop at the first ">", and show only the first author.
>
> Older versions of git would then get the date wrong, complaining about
> the ",". Newer versions parse the date from right-to-left to work around
> such bogosities (especially things like "<foo <bar>>") and so will parse
> back to the second ">".
>
> Fsck will definitely complain about it.

Ah, that is a problem.

If I remember correctly, I have seen somewhere using Bob+Alice for the name part and <bob+alice@example.com> or <bob@emai.l+alice@em.ail> for the email part... Would this work, I wonder?

[hoping that Thunderbird email didn;t screw up formatting]

-- 
Jakub Narębski