Re: [PATCH] git-clone.txt: Adjust note to --shared for new pruning behavior of git-gc

From: Brandon Casey <casey@nrlssc.navy.mil>
Date: Apr 3, 2008, 20:51 UTC
Message-ID: <47F54342.1040901@nrlssc.navy.mil>
In-Reply-To: <alpine.LSU.1.00.0804032113280.4008@racer.site>

Johannes Schindelin wrote:

Show 26 quoted lines

> Hi,
> 
> On Thu, 3 Apr 2008, Brandon Casey wrote:
> 
>> diff --git a/Documentation/git-clone.txt b/Documentation/git-clone.txt
>> index 9758243..d3ab00b 100644
>> --- a/Documentation/git-clone.txt
>> +++ b/Documentation/git-clone.txt
>> @@ -65,10 +65,12 @@ OPTIONS
>>  +
>>  *NOTE*: this is a possibly dangerous operation; do *not* use
>>  it unless you understand what it does. If you clone your
>> -repository using this option, then delete branches in the
>> -source repository and then run linkgit:git-gc[1] using the
>> -'--prune' option in the source repository, it may remove
>> -objects which are referenced by the cloned repository.
>> +repository using this option and then delete branches in the
>> +source repository, some objects may become unreferenced (or dangling).
>> +These objects may be removed by normal git operations (such as git-commit[1])
>> +which automatically call git-gc[1]. If these objects are removed and
>> +were referenced by the cloned repository, then the cloned repository
>> +will become corrupt.
> 
> Please note that if you delete a branch _after_ running git-gc, the next 
> git-gc would remove those objects anyway, since the first git-gc packed 
> the objects, and they were therefore no longer dangling.

I thought they would be retained unless --prune was used. git-gc uses the -A option to repack when --prune is not used and -a when --prune is used.

I think even with the new prune behavior they would still be retained as long as they were packed since the prune only affects loose objects.

> So it was an issue before the new git-gc behaviour anyway.

Well, I thought that git-gc had become "safe" with respect to --shared repositories ever since the call to repack started using -A when --prune was not used.

Now it is unsafe again. But what I was really trying to point out in the documentation changes was that now _other_ commands such as git-commit are also unsafe since they call 'git-gc --auto' and could cause loose unreferenced objects to be deleted. So it is not enough to just avoid calling git-gc when dealing with a --shared repository.

-brandon