[tahoe-dev] py-zfec on github now includes darcs history
Zancas Dearana
zancas at leastauthority.com
Thu Jun 13 18:41:27 UTC 2013
On Sun, Jun 9, 2013 at 3:33 PM, Richard Kiss <him at richardkiss.com> wrote:
> I realized I should just rebase on the darcs history import I produced, so
> the github repo at
>
> https://github.com/richardkiss/py-zfec
>
> is now rebased with the darcs history.
>
> In darcs, the top level included misc and zfec. I moved everything in zfec
> to the top level so it would be a little more standard, and so the
> README.rst file would display. This might break build scripts, but if so,
> they should be easy to fix (substitute zfec/zfec => zfec). Feel free to use
> this as a github base (ie. if you do a clone and push, I'll delete my
> version).
>
> --
> http://richardkiss.com/
>
I don't know which tool you used to port darcs-to-git, and you may
already be aware of this, but if you're not, you should know that there is
a discrepancy in the way that darcs records patches, and git records
commits.
Git does not record commits of empty trees.
A git blob is a sha1 indexed object that includes (among other things) the
data in a file.
A git tree is an object with a reference to a blob, or to another tree.
An important caveat is that there must be at least one blob referred to by
a tree (even if the reference is indirect via multiple trees), for that
tree to exist.
In git file contents are mapped into blobs, and directory contents are
mapped into trees. Unfortunately, this means that there is not a map from
an empty directory into a git object, because an empty directory contains
no files-or-directories, and git-trees are required to refer to at least
one blob.
In darcs on the other hand an empty directory can be added as its own patch.
The result of this discrepancy between data models is that porting tools
must make a decision about how to report darcs patches that correspond to
the addition of a single directory. I don't know if this is an issue in
the zfec code base, but it's something that "porters" ought to be aware of.
--
-- ظ
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