Re: How to create a new branch based on a tag?

Junio C Hamano wrote:

>Ben Lau <benlau@ust.hk> writes:
>
>  
>
>>>The way you know is as good as it gets.  v2.6.11-tree case is
>>>really an unfortunate special case.
>>>
>>>      
>>>
>>What is wrong with the v2.6.11-tree? I just thought it is a duplicate tag
>>of v2.6.11.
>>    
>>
>
>They are not *wrong* per-se.  They are tags to tree objects
>without any associated commit history -- that makes them
>inappropriate to be used as branch heads.
>
>Linus or somebody authoritative could do:
>
>    $ commit=$(echo v2.6.11 | \
>      git-commit-tree c39ae07f393806ccf406ef966e9a15afc43cc36a)
>    $ git-tag -s -m 'v2.6.11 canonical "fake" commit' v2.6.11fake $commit
>
>and tell everybody interested to have:
>
>1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 xxxxxxxxxx
>
>(where xxxxx... is the value of $commit above) in their
>info/grafts file.  Then we *could* pretend that v2.6.12-rc2's
>parent is v2.6.11.  You could branch off from v2.6.11fake commit
>and base your development, and later you could merge that into
>later development history (say, v2.6.14-rc5) if you wanted to.
>
>If Linus does something like the above, the graft probably be
>better done between the current v2.6.12-rc2 based commit history
>and the corresponding commit in the history resurrected from
>BKCVS (torvalds/old-2.6-bkcvs.git).  Then you could even base
>your development on top of v2.4.0 ;-).
>
>Funnily, v2.6.12-rc2 commit in the current history and BKCVS
>v2.6.12-rc2 commit in the resurrected history have different
>tree IDs.
>
>I am however not quite sure how useful the above would be,
>though.  EVen between 2.6.11 and 2.6.12-rc2 much have happened,
>so unless the changes you are making apply to the part that did
>not change between those two, merge conflict resolution might be
>quite a chore.
>
>
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>  
>
Thanks for detail explanation.

It is a little bit difficult for me. The result of `git log`
shows that the eldest commit is 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2
which is linux-2.6.12-rc2. Is that means the git repository do not
store the history before this tag? Then how can `git-read-tree
v2.6.11`  fetchs the content of v2.6.11?

By the way, How could you find the 
c39ae07f393806ccf406ef966e9a15afc43cc36a out?

I have followed your instuctions and now have my own 2.6.11 
branch(my2.6.11). Should be fine
now. Many thanks to all you guys.

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