threads / discuss / 24820

git-describe --contains fails on given tree

Subject: git-describe --contains fails on given tree

## tl;dr

5 messages between Aug 21, 2010 and Aug 23, 2010.

replies: 4people: 3as markdown or json

Jan Engelhardt· Aug 21, 2010, 19:47 UTC · lore

Hi,

for some reason, git-describe cannot figure out v1.17~15^2^2 in the pam_mount tree, despite me being able to actually give a description that would fit the contains syntax:

$ git clone git://pam-mount.git.sf.net/gitroot/pam-mount/pam-mount Initialized empty Git repository in /dev/shm/pam-mount/.git/ remote: Counting objects: 7261, done. remote: Compressing objects: 100% (1819/1819), done. remote: Total 7261 (delta 5557), reused 6990 (delta 5348) Receiving objects: 100% (7261/7261), 1.40 MiB | 832 KiB/s, done. Resolving deltas: 100% (5557/5557), done.

$ cd pam-mount/ $ git describe --contains v1.17~15^2^2 fatal: cannot describe '95ce932690dfce8cbe50b6a3a8949e41a54c8966'

(Expected to get back: v1.17~15^2^2)

Why would it not want to return something? Possible bug?

Using git 1.7.1 on openSUSE 11.3.

thanks, Jan

Jakub Narebski· Aug 21, 2010, 19:55 UTC · re: Jan Engelhardt · lore

Re: git-describe --contains fails on given tree

Jan Engelhardt <jengelh@medozas.de> writes:

Show 24 quoted lines

> Hi,
> 
> 
> 
> for some reason, git-describe cannot figure out v1.17~15^2^2 in
> the pam_mount tree, despite me being able to actually give
> a description that would fit the contains syntax:
> 
> $ git clone
> git://pam-mount.git.sf.net/gitroot/pam-mount/pam-mount
> Initialized empty Git repository in /dev/shm/pam-mount/.git/
> remote: Counting objects: 7261, done.
> remote: Compressing objects: 100% (1819/1819), done.
> remote: Total 7261 (delta 5557), reused 6990 (delta 5348)
> Receiving objects: 100% (7261/7261), 1.40 MiB | 832 KiB/s, done.
> Resolving deltas: 100% (5557/5557), done.
> 
> $ cd pam-mount/
> $ git describe --contains v1.17~15^2^2
> fatal: cannot describe '95ce932690dfce8cbe50b6a3a8949e41a54c8966'
> 
> (Expected to get back: v1.17~15^2^2)
> 
> Why would it not want to return something? Possible bug?

Is v1.17 an *annotated* tag?  What does

  $ git describe --contains --tags v1.17~15^2^2

return?

-- 
Jakub Narebski
Poland
ShadeHawk on #git

Jan Engelhardt· Aug 21, 2010, 20:42 UTC · re: Jakub Narebski · lore

Re: git-describe --contains fails on given tree

On Saturday 2010-08-21 21:55, Jakub Narebski wrote:

Show 22 quoted lines

>> for some reason, git-describe cannot figure out v1.17~15^2^2 in
>> the pam_mount tree, despite me being able to actually give
>> a description that would fit the contains syntax:
>> 
>> $ git clone
>> git://pam-mount.git.sf.net/gitroot/pam-mount/pam-mount
>> Initialized empty Git repository in /dev/shm/pam-mount/.git/
>> remote: Counting objects: 7261, done.
>> remote: Compressing objects: 100% (1819/1819), done.
>> remote: Total 7261 (delta 5557), reused 6990 (delta 5348)
>> Receiving objects: 100% (7261/7261), 1.40 MiB | 832 KiB/s, done.
>> Resolving deltas: 100% (5557/5557), done.
>> 
>> $ cd pam-mount/
>> $ git describe --contains v1.17~15^2^2
>> fatal: cannot describe '95ce932690dfce8cbe50b6a3a8949e41a54c8966'
>> 
>> (Expected to get back: v1.17~15^2^2)
>> 
>> Why would it not want to return something? Possible bug?
>
>Is v1.17 an *annotated* tag?

It certainly is (if it were not, there be no tag, just commit):

$ git show v1.17
tag v1.17
Tagger: Jan Engelhardt <jengelh@medozas.de>
Date:   Mon Jan 26 00:41:17 2009 +0100

pam_mount 1.17
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.9 (GNU/Linux)

iEYEABECAAYFAkl8+J8ACgkQ92gFgoRMQ2Dd7QCeJj/u543aBiK/Los8LgvdkR/1 6nwAnA/CB23vjxFpVWsKZIW99GHxDglX =yLqV -----END PGP SIGNATURE-----

>What does
>
>  $ git describe --contains --tags v1.17~15^2^2

"Cannot describe 95ce..."

Funny thing is, describing "v1.17~15^2" does work, as does "v1.17~15^1".

Thomas Rast· Aug 22, 2010, 21:58 UTC · re: Jan Engelhardt · lore

Re: git-describe --contains fails on given tree

Jan Engelhardt wrote:

Show 12 quoted lines

> 
> On Saturday 2010-08-21 21:55, Jakub Narebski wrote:
> >> for some reason, git-describe cannot figure out v1.17~15^2^2 in
> >> the pam_mount tree, despite me being able to actually give
> >> a description that would fit the contains syntax:
> >What does
> >
> >  $ git describe --contains --tags v1.17~15^2^2
> 
> "Cannot describe 95ce..."
> 
> Funny thing is, describing "v1.17~15^2" does work, as does "v1.17~15^1".

That's clock skew:

  $ git show -s --format="%cd" v1.17~15^2 
  Fri Jan 9 04:35:59 2009 +0100

  $ git show -s --format="%cd" v1.17~15^2^2
  Sat Jan 24 16:35:34 2009 +0100

Note how the parent commit is far newer than the child. git-name-rev (which is what really drives git describe --contains) concludes that it can stop searching along this line of history.

Interestingly, --stdin disables this optimization:

  $ git rev-parse v1.17~15^2^2 | git name-rev --stdin
  95ce932690dfce8cbe50b6a3a8949e41a54c8966 (tags/v1.17~15^2^2)

-- 
Thomas Rast
trast@{inf,student}.ethz.ch

Jan Engelhardt· Aug 23, 2010, 11:26 UTC · re: Thomas Rast · lore

Re: git-describe --contains fails on given tree

On Sunday 2010-08-22 23:58, Thomas Rast wrote:

Show 19 quoted lines

>> On Saturday 2010-08-21 21:55, Jakub Narebski wrote:
>> >> for some reason, git-describe cannot figure out v1.17~15^2^2 in
>> >> the pam_mount tree, despite me being able to actually give
>> >> a description that would fit the contains syntax:
>> >What does
>> >
>> >  $ git describe --contains --tags v1.17~15^2^2
>> 
>> "Cannot describe 95ce..."
>> 
>> Funny thing is, describing "v1.17~15^2" does work, as does "v1.17~15^1".
>
>That's clock skew:
>
>  $ git show -s --format="%cd" v1.17~15^2 
>  Fri Jan 9 04:35:59 2009 +0100
>
>  $ git show -s --format="%cd" v1.17~15^2^2
>  Sat Jan 24 16:35:34 2009 +0100

Thanks for pointing that out. (Ah the joy of BSD-inside-VMware.)

>Interestingly, --stdin disables this optimization:
>
>  $ git rev-parse v1.17~15^2^2 | git name-rev --stdin
>  95ce932690dfce8cbe50b6a3a8949e41a54c8966 (tags/v1.17~15^2^2)