Hello,
I'm implementing Git using node.js, and I have a question while I
write some code to store tree object.
Tree object looks a table consists of three fields: blob's mode, name
and id, as below.
e.g.)
$ git cat-file -p 45799547
100644 blob cd242b1e5bb403500feb49a1aa656c21c6c0be69 Makefile
100644 blob bf382321749577d52bd2fbf2281df0510b4bad31 README.md
100644 blob 5441bb48428611a3cb140d8192d39484fcf3b742 fsutil.js
100644 blob 0af680a5c0dd4482b09aa7f8e837234bed0b7cfa package.json
040000 tree 39a4d45669addfb1e8f0a499deebc5b97b4edfa0 test
It seems that the table is stored in order by blob's name.
If it is true, what happens if it is not ordered?
Does that cause any troubles to users to use a git repository created
and managed by my Git implementation?
On Sun, 2012-04-08 at 12:43 +0900, Yi, EungJun wrote:
Hello,
I'm implementing Git using node.js, and I have a question while I
write some code to store tree object.
Tree object looks a table consists of three fields: blob's mode, name
and id, as below.
e.g.)
$ git cat-file -p 45799547
100644 blob cd242b1e5bb403500feb49a1aa656c21c6c0be69 Makefile
100644 blob bf382321749577d52bd2fbf2281df0510b4bad31 README.md
100644 blob 5441bb48428611a3cb140d8192d39484fcf3b742 fsutil.js
100644 blob 0af680a5c0dd4482b09aa7f8e837234bed0b7cfa package.json
040000 tree 39a4d45669addfb1e8f0a499deebc5b97b4edfa0 test
It seems that the table is stored in order by blob's name.
Yes, the entries in the tree are alpha-sorted. The exception are trees,
where you have to pretend that there is a trailing slash. In other
words, the order is the same as you'd see in the index (as there, the
test/ directory in your example would be stored with a slash and the
name of the subdirs and files in it.
If it is true, what happens if it is not ordered?
fsck complains for one.
Does that cause any troubles to users to use a git repository created
and managed by my Git implementation?
How does your implementation store things? You haven't said (maybe
hinted that you may be writing trees with the wrong order). Depending on
the particular implementation of whatever is reading the git repository,
it might not be able to find an entry in your tree, as it's wrongly
sorted, but that depends on the exact implementation and possibly luck.
Do you need to write this in pure js? There are some bindings for
node.js[0] already for libgit2 so you don't need to redo the low-level
work.
Cheers,
cmn
[0] https://github.com/libgit2/node-gitteh
You are right. I tried to clone a repository which has a unordered
tree object and all you said happened, as below.
$ git ls-tree HEAD
100644 blob a6ccb8dec6b21e9d3e0b716d3a0915262a8c4474 b
100644 blob a3df8f3749f855a2d905d92f11590a9c18a1bcbb a
100644 blob 424907d3fe9f1fa4b2e3a0bb65ab99780d9acfba c
$ git show -- b
$ git show -- a
$ git fsck
error in tree 3f5a56e992a01f2e500bed57360f3961323b9d6e: not properly sorted
error in tree a94e7dc2820eb4d0ef308fac1a32b3715e82dc76: not properly sorted
I want to allow users to clone the git repository created by my implementation,
but before I have to sort tree objects. Thanks to you, I know that now.
And your suggestion to use node-gitteh is also thankful,
but I want pure js implementation without libgit2.
2012년 4월 8일 오후 10:20, Carlos Martín Nieto [off-list ref]님의 말:
On Sun, 2012-04-08 at 12:43 +0900, Yi, EungJun wrote:
quoted
Hello,
I'm implementing Git using node.js, and I have a question while I
write some code to store tree object.
Tree object looks a table consists of three fields: blob's mode, name
and id, as below.
e.g.)
$ git cat-file -p 45799547
100644 blob cd242b1e5bb403500feb49a1aa656c21c6c0be69 Makefile
100644 blob bf382321749577d52bd2fbf2281df0510b4bad31 README.md
100644 blob 5441bb48428611a3cb140d8192d39484fcf3b742 fsutil.js
100644 blob 0af680a5c0dd4482b09aa7f8e837234bed0b7cfa package.json
040000 tree 39a4d45669addfb1e8f0a499deebc5b97b4edfa0 test
It seems that the table is stored in order by blob's name.
Yes, the entries in the tree are alpha-sorted. The exception are trees,
where you have to pretend that there is a trailing slash. In other
words, the order is the same as you'd see in the index (as there, the
test/ directory in your example would be stored with a slash and the
name of the subdirs and files in it.
quoted
If it is true, what happens if it is not ordered?
fsck complains for one.
quoted
Does that cause any troubles to users to use a git repository created
and managed by my Git implementation?
How does your implementation store things? You haven't said (maybe
hinted that you may be writing trees with the wrong order). Depending on
the particular implementation of whatever is reading the git repository,
it might not be able to find an entry in your tree, as it's wrongly
sorted, but that depends on the exact implementation and possibly luck.
Do you need to write this in pure js? There are some bindings for
node.js[0] already for libgit2 so you don't need to redo the low-level
work.
Cheers,
cmn
[0] https://github.com/libgit2/node-gitteh