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From: Junio C Hamano <gitster@pobox.com>
To: Benno Evers <benno@bmevers.de>
Cc: git@vger.kernel.org, spearce@spearce.org
Subject: Re: [PATCH] describe: dont abort too early when searching tags
Date: Mon, 24 Feb 2020 12:52:52 -0800	[thread overview]
Message-ID: <xmqq4kvfpv17.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <20200223125102.6697-1-benno@bmevers.de> (Benno Evers's message of "Sun, 23 Feb 2020 13:51:02 +0100")

Benno Evers <benno@bmevers.de> writes:

> When searching the commit graph for tag candidates, `git-describe`
> will stop as soon as there is only one active branch left and
> it already found an annotated tag as a candidate.
>
> This works well as long as all branches eventually connect back
> to a common root, but if the tags are found across branches
> with no common ancestor
>
>                   B
>                   o----.
>                         \
>           o-----o---o----x
>           A
>
> it can happen that the search on one branch terminates prematurely
> because a tag was found on another, independent branch. This scenario
> isn't quite as obscure as it sounds, since cloning with a limited
> depth often introduces many independent "dead ends" into the commit
> graph.
>
> The help text of `git-describe` states pretty clearly that when
> describing a commit D, the number appended to the emitted tag X should
> correspond to the number of commits found by `git log X..D`.

To be fair, that description was written for the case in a normal
history with only a single root.

How much, if any, does this change hurt the performance by forcing
the code to dig further if there aren't multiple roots?  If there is
such an unnecessary overhead that degrades performance for the more
common case, can we improve it further to avoid it?

Thanks.




  reply	other threads:[~2020-02-24 20:52 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-23 12:51 [PATCH] describe: dont abort too early when searching tags Benno Evers
2020-02-24 20:52 ` Junio C Hamano [this message]
2020-02-25 19:07   ` benno
2020-02-25 20:10     ` Junio C Hamano
2021-02-28 19:54 ` [PATCH 00/10] describe tests: refactor & fix recent broken tests Ævar Arnfjörð Bjarmason
2021-03-09  0:47   ` Junio C Hamano
2021-03-12 23:59   ` Junio C Hamano
2021-04-12 11:21   ` [PATCH v2 0/5] describe test fixes Ævar Arnfjörð Bjarmason
2021-04-12 11:21     ` [PATCH v2 1/5] describe tests: improve test for --work-tree & --dirty Ævar Arnfjörð Bjarmason
2021-04-12 11:21     ` [PATCH v2 2/5] describe tests: refactor away from glob matching Ævar Arnfjörð Bjarmason
2021-04-12 11:21     ` [PATCH v2 3/5] describe tests: don't rely on err.actual from "check_describe" Ævar Arnfjörð Bjarmason
2021-04-12 11:21     ` [PATCH v2 4/5] describe tests: fix nested "test_expect_success" call Ævar Arnfjörð Bjarmason
2021-04-12 11:21     ` [PATCH v2 5/5] describe tests: support -C in "check_describe" Ævar Arnfjörð Bjarmason
2021-04-12 11:33   ` [PATCH v2 0/2] svn tests: trivial "set -e" in main body of test fixes Ævar Arnfjörð Bjarmason
2021-04-12 11:33     ` [PATCH v2 1/2] svn tests: remove legacy re-setup from init-clone test Ævar Arnfjörð Bjarmason
2021-04-12 11:33     ` [PATCH v2 2/2] svn tests: refactor away a "set -e" in test body Ævar Arnfjörð Bjarmason
2021-02-28 19:54 ` [PATCH 01/10] describe tests: improve test for --work-tree & --dirty Ævar Arnfjörð Bjarmason
2021-02-28 19:54 ` [PATCH 02/10] describe tests: refactor away from glob matching Ævar Arnfjörð Bjarmason
2021-03-01 21:26   ` Junio C Hamano
2021-02-28 19:54 ` [PATCH 03/10] describe tests: always assert empty stderr from "describe" Ævar Arnfjörð Bjarmason
2021-03-01 21:32   ` Junio C Hamano
2021-02-28 19:54 ` [PATCH 04/10] test-lib functions: add an --annotated-tag option to "test_commit" Ævar Arnfjörð Bjarmason
2021-03-01 21:41   ` Junio C Hamano
2021-03-02  9:34     ` Ævar Arnfjörð Bjarmason
2021-03-03  6:35       ` Junio C Hamano
2021-02-28 19:54 ` [PATCH 05/10] describe tests: convert setup to use test_commit Ævar Arnfjörð Bjarmason
2021-03-01 21:42   ` Junio C Hamano
2021-02-28 19:54 ` [PATCH 06/10] describe tests: fix nested "test_expect_success" call Ævar Arnfjörð Bjarmason
2021-02-28 19:54 ` [PATCH 07/10] describe tests: support -C in "check_describe" Ævar Arnfjörð Bjarmason
2021-02-28 19:54 ` [PATCH 08/10] svn tests: remove legacy re-setup from init-clone test Ævar Arnfjörð Bjarmason
2021-02-28 19:54 ` [PATCH 09/10] svn tests: refactor away a "set -e" in test body Ævar Arnfjörð Bjarmason
2021-02-28 21:14   ` Eric Wong
2021-02-28 19:54 ` [PATCH 10/10] test-lib: return 1 from test_expect_{success,failure} Ævar Arnfjörð Bjarmason
2021-03-01 21:43   ` Junio C Hamano

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