Re: Mercurial vs Updated git HOWTO for kernel hackers
- From
Horst von Brand <vonbrand@inf.utfsm.cl>
- Date
- Jun 28, 2005, 21:54 UTC
- Message-ID
- <200506282154.j5SLsETL010486@laptop11.inf.utfsm.cl>
- In-Reply-To
- <andrewkt@aktzero.com>
Andrew Thompson <andrewkt@aktzero.com> wrote:
> Petr Baudis wrote:
> >>Mercurial's undo is taking a snapshot of all the changed file's repo > >>file length at every commit or pull. It just truncate the file to > >>original size and undo is done.
> > "Trunactes"? That sounds very wrong... you mean replace with old > > version? Anyway, what if the file has same length? It just doesn't make > > much sense to me.
> I believe this works because the files stored in a binary format that > appends new changesets onto the end. Thus, truncating the new stuff > from the end effectively removes the commit.
And is exactly the wrong way around. Even RCS stored the _last_ version and differences to earlier ones (you'll normally want the last one (or something near), and so occasionally having to reconstruct earlier ones by going back isn't a big deal; having to build up the current version by starting from /dev/null and applying each and every patch that ever touched the file each time is expensive given enough history, besides that any error in the file is guaranteed to destroy the current version, not (hopefully) just making old versions unavailable). It also means that losing old history (what you'll want to do once in a while, e.g. forget everything before 2.8) is simple: Chop off at the right point.
-- Dr. Horst H. von Brand User #22616 counter.li.org Departamento de Informatica Fono: +56 32 654431 Universidad Tecnica Federico Santa Maria +56 32 654239 Casilla 110-V, Valparaiso, Chile Fax: +56 32 797513