Re: [PATCH 2/2] name-rev: favor describing with tags and use committer date to tiebreak

[Lars Schneider <larsxschneider@gmail.com>]

> On 16 Mar 2017, at 06:50, Junio C Hamano <gitster@pobox.com> wrote:
> 
> "git name-rev" assigned a phony "far in the future" date to tips of
> refs that are not pointing at tag objects, and favored names based
> on a ref with the oldest date.  This made it almost impossible for
> an unannotated tags and branches to be counted as a viable base,
> which was especially problematic when the command is run with the
> "--tags" option.  If an unannotated tag that points at an ancient
> commit and an annotated tag that points at a much newer commit
> reaches the commit that is being named, the old unannotated tag was
> ignored.
> 
> Update the "taggerdate" field of the rev-name structure, which is
> initialized from the tip of ref, to have the committer date if the
> object at the tip of ref is a commit, not a tag, so that we can
> optionally take it into account when doing "is this name better?"
> comparison logic.
> 
> When "name-rev" is run without the "--tags" option, the general
> expectation is still to name the commit based on a tag if possible,
> but use non-tag refs as fallback, and tiebreak among these non-tag
> refs by favoring names with shorter hops from the tip.  The use of a
> phony "far in the future" date in the original code was an effective
> way to ensure this expectation is held: a non-tag tip gets the same
> "far in the future" timestamp, giving precedence to tags, and among
> non-tag tips, names with shorter hops are preferred over longer
> hops, without taking the "taggerdate" into account.  As we are
> taking over the "taggerdate" field to store the committer date for
> tips with commits:
> 
> (1) keep the original logic when comparing names based on two refs
>     both of which are from refs/tags/;
> 
> (2) favoring a name based on a ref in refs/tags/ hierarchy over
>     a ref outside the hierarchy;
> 
> (3) between two names based on a ref both outside refs/tags/, give
>     precedence to a name with shorter hops and use "taggerdate"
>     only to tie-break.
> 
> A change to t4202 is a natural consequence.  The test creates a
> commit on a branch "side" and points at it with an unannotated tag
> "refs/tags/side-2".  The original code couldn't decide which one to
> favor at all, and gave a name based on a branch (simply because
> refs/heads/side sorts earlier than refs/tags/side-2).  Because the
> updated logic is taught to favor refs in refs/tags/ hierarchy, the
> the test is updated to expect to see tags/side-2 instead.
> 
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---

A quick bisect indicates that this patch might break 
t9807-git-p4-submit.sh 8 and 13. I haven't looked into
it further, yet.

https://travis-ci.org/git/git/jobs/211948406#L2152
https://travis-ci.org/git/git/jobs/211948406#L2460

Non-JS: https://s3.amazonaws.com/archive.travis-ci.org/jobs/211948406/log.txt

- Lars