Re: publish from certain commit onward, keeping earlier history private, but provable
On Wed, Dec 09, 2015 at 02:29:12PM -0800, Stefan Beller wrote: > On Wed, Dec 9, 2015 at 2:24 PM, Jeff King wrote: > > On Wed, Dec 09, 2015 at 05:20:41PM -0500, Jeff King wrote: > > > >> Of course that is a bitter pill to swallow if you have reasons for > >> wanting to use the old sha1s. E.g., you have internal development > >> proceeding against the old tree and want to share a truncated version > >> with the public. > > > > After re-reading your email, it looks like your use case is just to be > > able to later prove the existence of the original history. You could > > that by mentioning the original "C" in your truncated "D", but in a way > > that git does not traverse reachability. For instance, amend D's commit > > message to say: > > > > This is based on earlier, unpublished work going up to commit C. > > > > Then retain C for yourself, and show it only to those you want to prove > > its contents to. > > I'd rather keep D for yourself and create a D' which is D just without > parent and > the note above, such that the tree of D and parts of the commit message > is obvious by looking at D'. All that is secret is Ds parent and the commit > information such as exact date. (committer could be guessed easily) I think the point is that all of this is happening at time t (let's say 2015), and the proof may be needed at time t+N (let's say 2020). Showing the original D (or C, or whatever) at that point proves nothing, as you could have created a fake history in 2020 that "ends up" at the D' tree. You need to publish _something_ in 2015 that says "I know this thing, but I am not willing to show it to you yet". The classic way of doing this is to take out a small ad in the classified section of a print newspaper with a hash of your data. Libraries keep archives of the paper, so later you can prove that you have the data that matches the hash, and its timestamp is certified by the library archives. Here we're abusing Git as the notary. If everyone spends the years from 2015-2020 building on top of D', then they can all reasonably agree that the content of D' was written in 2015, and any commit hash it mentions had to have existed then. Revealing C (or the original D, or whatever hash you want to mention) proves the data. -Peff -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: publish from certain commit onward, keeping earlier history private, but provable
On Wed, Dec 9, 2015 at 2:24 PM, Jeff King wrote: > On Wed, Dec 09, 2015 at 05:20:41PM -0500, Jeff King wrote: > >> Of course that is a bitter pill to swallow if you have reasons for >> wanting to use the old sha1s. E.g., you have internal development >> proceeding against the old tree and want to share a truncated version >> with the public. > > After re-reading your email, it looks like your use case is just to be > able to later prove the existence of the original history. You could > that by mentioning the original "C" in your truncated "D", but in a way > that git does not traverse reachability. For instance, amend D's commit > message to say: > > This is based on earlier, unpublished work going up to commit C. > > Then retain C for yourself, and show it only to those you want to prove > its contents to. I'd rather keep D for yourself and create a D' which is D just without parent and the note above, such that the tree of D and parts of the commit message is obvious by looking at D'. All that is secret is Ds parent and the commit information such as exact date. (committer could be guessed easily) > > -Peff > -- > To unsubscribe from this list: send the line "unsubscribe git" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: publish from certain commit onward, keeping earlier history private, but provable
On Wed, Dec 09, 2015 at 05:20:41PM -0500, Jeff King wrote: > Of course that is a bitter pill to swallow if you have reasons for > wanting to use the old sha1s. E.g., you have internal development > proceeding against the old tree and want to share a truncated version > with the public. After re-reading your email, it looks like your use case is just to be able to later prove the existence of the original history. You could that by mentioning the original "C" in your truncated "D", but in a way that git does not traverse reachability. For instance, amend D's commit message to say: This is based on earlier, unpublished work going up to commit C. Then retain C for yourself, and show it only to those you want to prove its contents to. -Peff -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: publish from certain commit onward, keeping earlier history private, but provable
On Wed, Dec 09, 2015 at 02:45:44PM +0100, Jörn Hees wrote: > I've been hacking away on a library for quite some time and have a lot of > commits in my private repository: > > A -> B -> C -> D -> E > > Finally, I'm nearing completion of a first version, and want to > publish it to a remote called public from D onward keeping A..C to > myself, so public should afterwards look like this: > > D -> E The short answer is that you cannot do this without changing the names (i.e., sha1 commit ids) of D and E. One of the fundamental assumptions git makes is that if a repository has an object X, it also has all of the objects reachable from it (past commits, their trees, subtrees, and blobs). This is what makes the push/fetch object transfer efficient (one side says only "I have X" and the other side knows "Ah, that is a whole chunk of objects I do not have to bother sending", without the names of those objects going over the wire). The exception, of course, is shallow clones, where one side tells the other "I am shallow at cutoff point Y; don't assume I have anything below there". This does work, but there are some downsides (for instance, we cannot apply some of the same reachability optimizations for serving fetches). > I can verify that local_public only contains D -> E and that the > commit, tree and parent hashes are the same, which is exactly what i > want. > > The problem is that when i try to push to an added public remote > from local_public i get an error like this: > > ! [remote rejected] master -> master (shallow update not allowed) Right. The receiver must be explicitly configured to accept a shallow push (I do not recall offhand whether clients fetching from you would also need an explicit config to accept a shallow history). So the usual path here is to rewrite D and E (with the same trees, but they will get new commit ids). If you want to retain the older history (commits A-C), you can distribute it separately and use git-replace to "graft" it onto the newer history at run-time. You can do that with: # set up a run-time replacement view so that D appears to have # no parents; this doesn't impact the objects themselves, but # rather git will use our parent-less "replacement" D anytime # somebody mentions the original git replace --graft D # verify that the history is what you want; if you have a non-linear # history you may have to make several such "cuts" in the graph git log # now cement it into place by rewriting git filter-branch Of course that is a bitter pill to swallow if you have reasons for wanting to use the old sha1s. E.g., you have internal development proceeding against the old tree and want to share a truncated version with the public. In that case I still think the least painful thing is to rewrite the truncated history, have _everyone_, internal and public work against that, and let internal folks graft the old history on for their own use. They can do that with: git replace --graft the-rewritten-D the-original-C -Peff -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: publish from certain commit onward, keeping earlier history private, but provable
On 09/12, Jörn Hees wrote: Hi, I've been hacking away on a library for quite some time and have a lot of commits in my private repository: A -> B -> C -> D -> E Finally, I'm nearing completion of a first version, and want to publish it to a remote called public from D onward keeping A..C to myself, so public should afterwards look like this: D -> E My main motivation is that i don't really want to put ridiculously first trials online, but still (on demand) I'd like to be able to prove how i arrived at D (think of copyright claims, etc). As (at the moment) it's pretty much impossible to reverse-engineer the hashes of commits in the chain with times and changesets, i thought just keeping D's parent pointer to C would be one of the genius advantages of git. Sadly i can't find a way to actually make this work. Can i somehow push D -> E to public making it a fully functional public repository with all the necessary objects included to checkout D or E and D still pointing to C as parent? If not, why is that? Take a look at git-replace[0][1]. [0]: https://git-scm.com/2010/03/17/replace.html [1]: https://www.kernel.org/pub/software/scm/git/docs/git-replace.html -- Sincerely, Johannes Löthberg PGP Key ID: 0x50FB9B273A9D0BB5 https://theos.kyriasis.com/~kyrias/ signature.asc Description: PGP signature
publish from certain commit onward, keeping earlier history private, but provable
Hi, I've been hacking away on a library for quite some time and have a lot of commits in my private repository: A -> B -> C -> D -> E Finally, I'm nearing completion of a first version, and want to publish it to a remote called public from D onward keeping A..C to myself, so public should afterwards look like this: D -> E My main motivation is that i don't really want to put ridiculously first trials online, but still (on demand) I'd like to be able to prove how i arrived at D (think of copyright claims, etc). As (at the moment) it's pretty much impossible to reverse-engineer the hashes of commits in the chain with times and changesets, i thought just keeping D's parent pointer to C would be one of the genius advantages of git. Sadly i can't find a way to actually make this work. Can i somehow push D -> E to public making it a fully functional public repository with all the necessary objects included to checkout D or E and D still pointing to C as parent? If not, why is that? What doesn't seem to work: - push with range git push public D..E:master error: src refspec D..E does not match any. error: failed to push some refs to '' - any form of squashing / history rewriting As far as i know squashing A..D would introduce a new commit removing the parent pointer to C and thereby removing provability of the existence of A..C. (Simple example: say C reversed B, then you'd never be able to prove B was in there at some point.) I could obviously manually note the hash of C in the description of the squash commit, but there already is a parent pointer field, why not use it? Also in order to contribute further changes to public I'd have to rebase my private branches on top of this new squashed commit, which just seems as wrong... - push from local clone with limited depth I thought i found a solution to this by first creating a local clone local_public with the desired depth before pushing that clone to public like this: git clone --depth 2 file:/// local_public With git log --pretty=raw I can verify that local_public only contains D -> E and that the commit, tree and parent hashes are the same, which is exactly what i want. The problem is that when i try to push to an added public remote from local_public i get an error like this: ! [remote rejected] master -> master (shallow update not allowed) Any ideas how to make this work? Cheers, Jörn -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
