Date: Fri, 4 Dec 2015 11:53:39 -0800 From: Bryan Drewery <bdrewery@FreeBSD.org> To: =?UTF-8?Q?Ulrich_Sp=c3=b6rlein?= <uqs@FreeBSD.org>, freebsd-git@freebsd.org Cc: freebsd-current@freebsd.org, git-admin@freebsd.org Subject: Re: FYI: SVN to GIT converter currently broken, github is falling behind Message-ID: <5661EF43.9040406@FreeBSD.org> In-Reply-To: <CAJ9axoRV1gwpVsTpB_%2BPQX4ZrWpnJRtTJ77dsA0vC_BekR8=9g@mail.gmail.com> References: <CAJ9axoTuuBt4%2Bg4o1%2BLy9VmNfAa3pcMhcPr2ws8T1kCm=Om=tg@mail.gmail.com> <CAJ9axoRBcFD=-d=pzJJvYempEO-EyR_kAiK3EZQ_hp%2B7_J1iyQ@mail.gmail.com> <563EAAB8.5020702@freebsd.org> <CAJ9axoQmgT0B23UtmzGeMcvS%2BCHxC16FL53fPGObBZoxEC03aQ@mail.gmail.com> <CAJ9axoRcCUoLzyGN-JkJEn%2ByinWdVoSKUcBr7eas5638t6jBUg@mail.gmail.com> <CAJ9axoRV1gwpVsTpB_%2BPQX4ZrWpnJRtTJ77dsA0vC_BekR8=9g@mail.gmail.com>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --KIw4nppIcKxsRKMVRwiWAsIG3FSmtXmw6 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 12/4/2015 10:49 AM, Ulrich Sp=C3=B6rlein wrote: > 2015-11-08 12:06 GMT+01:00 Ulrich Sp=C3=B6rlein <uqs@freebsd.org>: >> 2015-11-08 11:32 GMT+01:00 Ulrich Sp=C3=B6rlein <uqs@freebsd.org>: >>> 2015-11-08 2:51 GMT+01:00 Alfred Perlstein <alfred@freebsd.org>: >>>>> >>>> Uli, >>>> >>>> One of the biggest concerns I've heard from folks using FreeBSD's gi= t mirror >>>> is that the hashes can change. >>>> >>>> I have a question about this. Is it possible to keep track of what= the >>>> "official" git mirror (on github) is doing and keep that as a log. = Then >>>> that log can be used to replay commits when there is a divergence pr= oblem. >>>> >>>> What I'm basically saying is that let's take this small example: >>>> >>>> importer is working fine @rev 10000 >>>> imports 10000 >>>> imports 10001 >>>> imports 10002 >>>> something happens to importer to give indeterminate shas. >>>> imports 10003 - sha is "unstable" sha3 >>>> imports 10004 - sha is "unstable" sha4 >>>> imports 10005 - sha is "unstable" sha5 >>>> imports 10006 - sha is "unstable" sha6 >>>> importer is fixed >>>> >>>> >>>> At this point normally we'd rewind the importer to 10002 and then fo= rce >>>> update the affected branches. >>>> >>>> My question is... can the imports of 10003, 10004, 10005 and 10006 b= e put >>>> into the importer such that any "mirror site" that re-does the impor= t using >>>> the most up to date importer will get the same shas. >>>> >>>> That would allow to proceed with 10007, etc without force pushing. >>>> >>>> This should be possible based on querying "git" for the meta data as= sociated >>>> with sha3..sha6 and then forcing those commits to have the same meta= data. >>>> >>>> This would eliminate the concern about shas in the mirror changing t= hat I've >>>> heard. >>> >>> The goal of the conversion is that everyone can re-do the conversion >>> in their basement and come up with the same history and checksums. >>> This was not the case when I first started, as there was some >>> non-deterministic hash structure being used in svn2git. This was fixe= d >>> in the code and then all converter runs produced the very same >>> results. >>> >>> The scenario that we have right now, is that one of the merge commits= >>> done about two weeks ago is being handled different by svn2git w/ svn= >>> v1.8 vs. svn v1.9 and I haven't investigated yet how the API's >>> behavior changed to cause this. I'm afraid I also swapped out all my >>> knowledge about svn2git internals and will have to redo this all from= >>> scratch :/ >>> >>> Your suggestion could only work, if we hard-code this svn revision >>> special handling into svn2git, either in the code or by providing mor= e >>> mappings and rules to the process. svn2git should run hermetic and no= t >>> poke at github's commits to see how things were handled in the past. >>> It has to be self-sufficient and must not depend on github. >>> >>> This would also only work, if the "breakage" window was very small, >>> but it is already about two weeks long and will surely increase till = I >>> find the proper fix. >>> >>> So, to take a stand here: this sort of kludge is unlikely to ever >>> happen. Git commit hashes *might* change in the future. I really don'= t >>> see how this is a big deal anyway. It happened once and I'm trying t= o >>> have it never happen again. But why are people afraid of this >>> happening? Every "official" git commit is tagged with a SVN revision >>> and the contents of those revisions are obviously correct (just not >>> the ancestry and the commit objects, possibly). So it would be easy t= o >>> write a script that replays VendorA's git history and swaps out the >>> new official commits for the old official commits. There would be no >>> merge conflicts. >>> >>> I can see how this would be annoying if you have 100 developers and >>> dozens of branches that are far from mainline FreeBSD. But I'm sure >>> these companies that depend on git will come forward and donate some >>> of their developer manpower to help me with keeping the converter >>> stable/deterministic. Right? Right? :) :) >>> >>> Cheers, >>> Uli >> >> Quick update: doc is so far unaffected by svn 1.9, but for ports, the >> drift happened as of Jul 18, so you'd need to special case a lot of >> commits. >> >> Here's the same commit, and the difference between 1.8 and 1.9: >> >> % git cat-file commit 803795d >> tree 7fc83aba022834da5c218114b09ad4640735bcc0 >> parent c96fb0418e545a569b5975b4d878a30a948c29d5 >> author olgeni <olgeni@FreeBSD.org> 1437203525 +0000 >> committer olgeni <olgeni@FreeBSD.org> 1437203525 +0000 >> >> Upgrade to version 0.4.1. >> % git cat-file commit 61ca43b >> tree 7fc83aba022834da5c218114b09ad4640735bcc0 >> parent c96fb0418e545a569b5975b4d878a30a948c29d5 >> author olgeni <olgeni@FreeBSD.org> 1437203529 +0000 >> committer olgeni <olgeni@FreeBSD.org> 1437203529 +0000 >> >> Upgrade to version 0.4.1. >> >> >> In case you don't see it, there's a 4s difference in the timestamps >> for authoring and committing. Here's the original: >> >> % svn log -vc392405 svn://svn.freebsd.org/ports >> ----------------------------------------------------------------------= -- >> r392405 | olgeni | 2015-07-18 09:12:05 +0200 (Sat, 18 Jul 2015) | 2 li= nes >> Changed paths: >> M /head/www/elixir-maru/Makefile >> M /head/www/elixir-maru/distinfo >> >> Upgrade to version 0.4.1. >> >> ----------------------------------------------------------------------= -- >> >> So yeah, svn 1.9 returned a timestamp that was off by 4s. WTF? >> >> For base it's actually even more complicated than I had thought so >> far. But let's take this one step at time ... >=20 > An update, which you won't like to hear: >=20 > SVN v1.9 is totally innocent, the API changed a little and has been > patched, this is not the source of the difference between the > currently published repo and a clean run. The difference stems from > the fact that the svnsync'ed copy on git.freebsd.org was poisoned and > is *NOT* in sync with our main repo. People tell me this is due to a > shortcoming of svnsync that can race and thus produce different > metadata for a commit, depending on when it is run. >=20 > This is a clusterfuck. >=20 > Both freebsd-base and freebsd-ports are no longer reproducible by > third-parties. It is only a matter of time when freebsd-doc is > affected. >=20 > clusteradm@ sadly has remained rather silent on this issue and unless > we can move the mirroring to rsync or syncthing or whatever I don't > see how the project can continue to provide a so-called git "mirror" >=20 Running svnsync in 2 places and then calling them mirrors seems odd. It's only needed once. (svnsync hurts global warming too). Then just rsync or use the git mirroring features. --=20 Regards, Bryan Drewery --KIw4nppIcKxsRKMVRwiWAsIG3FSmtXmw6 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQEcBAEBAgAGBQJWYe9DAAoJEDXXcbtuRpfPMpIIAM0eaiH62z729Usg40skt+Ys jrQqnWegG/AGi5ULgMBFlh7LivlmCPobnwQokX83aZEsBhUvPKtfQp7b9Y14QWO1 cful3FRd4VfK4ti2uI0FMHnKmvLyb2iEATSnUCdAf+J+zB4kK14kz2gGDOUrec2+ A83MGgk4bJFRi1wFeqtzO6ZfBjecQPyikXICxX+rNtYd8pMfuuepr2MyneISUzyv Whc40hYYdyw1AIGv1mtMJhn4VQkKwjiyhzjLmHUsm+RSDlAOoV0UY6EQeVnbXL/L msRpLxhB4qq5EghEjqbUuL8C5wkwt9JO/BrW0/hSQXuBHKRKiab2pPVxXCZ48Kg= =rPTF -----END PGP SIGNATURE----- --KIw4nppIcKxsRKMVRwiWAsIG3FSmtXmw6--
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