Mike Hommey <mh@xxxxxxxxxxxx> writes:
> On Mon, Aug 20, 2007 at 08:40:13PM +0200, David Kastrup <dak@xxxxxxx> wrote:
>> Mike Hommey <mh@xxxxxxxxxxxx> writes:
>>
>> > On Mon, Aug 20, 2007 at 07:58:43PM +0200, David Kastrup <dak@xxxxxxx> wrote:
>> >> > I also never understood why there were no permissions set on
>> >> > directories in trees...
>> >>
>> >> Because directories are not actually tracked. They are created and
>> >> deleted as-needed.
>> >
>> > I don't see why it would prevent to have a permission set to
>> > it... the permission technically can be recorded in the parent tree,
>> > along its sha1. Filesystems are also like this.
>>
>> No, they aren't. Filesystems don't create and delete directories on
>> the fly. If we record any information about a directory, deleting it
>> automagically would not be appropriate since we would lose information
>> that has not been explicitly deleted.
>
> git doesn't magically create directories either. It actually stores
> something about them: the hash of the tree object that represents
> them.
The tree object is not a representation of the directory in the file
system. It is a hierarchical hash in the repository, stored for
efficiency reasons.
> And it has permissions associated with these hashes.
No, with the files. Think again: the link between file system and
repository is the index, and the current index format has no
representation for trees or directories.
So git _can't_ store any information about a _directory_, since no
information about directories passes through the index.
> (...)
>> > I think i wasn't clear enough... I just wondered why the format for tree
>> > entries is something like (if you'd write it in perl):
>> > sprintf "%06o %s\0%s", $mode, $file, pack("H[40]", $sha1)
>>
>> Now I am sure I don't get your point.
>
> See what a raw tree object looks like:
> git-cat-file tree 708453d64796eb617cb8a1602959e00356693315
Well, a tree is a container for files (which in turn consist of their
permissions, file names, and blobs).
--
David Kastrup, Kriemhildstr. 15, 44793 Bochum
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