From: Thomas Rast Date: Mon, 06 May 2013 10:32:15 GMT Subject: Re: [PATCH 4/4] fast-import: only store commit objects Message-ID: <87ip2wflg0.fsf@linux-k42r.v.cablecom.net> In-Reply-To: <518785B3.3050606@alum.mit.edu> Michael Haggerty writes: > On 05/03/2013 08:23 PM, Felipe Contreras wrote: >> On Fri, May 3, 2013 at 12:56 PM, Thomas Rast wrote: >>> Felipe Contreras writes: >> >>> How do we know that this doesn't break any users of fast-import? Your >>> comment isn't very reassuring: >>> >>>> the vast majority of them will never be used again >>> >>> So what's with the minority? >> >> Actually I don't think there's any minority. If the client program >> doesn't store blobs, the blob marks are not used anyway. So there's no >> change. > > I haven't been following this conversation in detail, but your proposed > change sounds like something that would break cvs2git [1]. Let me > explain what cvs2git does and why: > > CVS stores all of the revisions of a single file in a single filename,v > file in rcsfile(5) format. The revisions are stored as deltas ordered > so that a single revision can be reconstructed from a single serial read > of the file. > > cvs2git reads each of these files once, reconstructing *all* of the > revisions for a file in a single go. It then pours them into a > git-fast-import stream as blobs and sets a mark on each blob. > > Only much later in the conversion does it have enough information to > reconstruct tree-wide commits. At that time it outputs git-fast-import > data (to a second file) defining the git commits and their ancestry. > The contents are defined by referring to the marks of blobs from the > first git-fast-import stream file. > > This strategy speeds up the conversion *enormously*. > > So if I understand correctly that you are proposing to stop allowing > marks on blob objects to be set and/or referred to later, then I object > vociferously. The proposed patch wants to stop writing marks (in --export-marks) for anything but commits. Does cvs2git depend on that? I.e., are you using two separate fast-import processes for the blob and tree/commit phases you describe above? -- Thomas Rast trast@{inf,student}.ethz.ch