Re: Bug: "git checkout -b" should be allowed in empty repo

On 01/30/2012 07:48 PM, Junio C Hamano wrote:

Michael Haggerty [off-list ref] writes:

quoted

[3] If commit 0000000 were treated specially, then there would be no
unborn branches but only branches pointing at the empty commit.  In that
case, my expectation would change--the old branch should be left
pointing at 0000000.  But currently git has no concept of an unborn
branch that is not HEAD.

And it probably is not a good thing to add such. Under that constraints,
HEAD that says refs/heads/foo where foo does not exist yet needs to be
special cased at places where it matters.

For that matter, even if we artificially created refs/heads/foo before any
commit is made and made it point at 0{40}, you would need to add special
cases to other parts of the system

No, the idea is to avoid special casing by making 0{40} into a real (but
empty) revision.

(e.g. "commit" needs to notice that the
result should be a root, not a child of 0{40};

No, commits that were previously generated as orphans *would* now be
generated as children of the special 0{40} commit.

"checkout other_branch"
needs to notice that it should refrain from running the equivalent of
"read-tree -m HEAD other_branch" because HEAD does not point at a real
tree;

No, it would merge the 0{40} commit with other_branch like usual,
resulting in the same contents as other_branch.  Indeed, if other_branch
is also ultimately a descendant of 0{40}, this would be like a
fast-forward merge.

etc.

This "etc" might include problems.

so it does not change the fact that the unborn branch is case
is special.

On the contrary, I believe that much special casing could be eliminated
and the UI made more uniform by treating everything as a descendant of a
special "NULL" commit.

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/