Bazaar Survival Guide updates (darcs, hg)

[Matt Nordhoff]

Ian Clatworthy wrote:
> A few days ago, I asked a few community members privately to help with
> the documentation that eases the transition to Bazaar from other tools.
> I'm pleased to announce some nice improvements along those lines:
> 
> * for Darcs users -
> http://doc.bazaar-vcs.org/migration/en/survival/bzr-for-darcs-users.html
> 
> * for Mercurial users -
> http://doc.bazaar-vcs.org/migration/en/survival/bzr-for-hg-users.html
> 
> Thanks for Miklos Vajna and Paul Moore respectively for their work here.
> If you're familiar with these tools, please take a look at these
> documents and suggest fixes/improvements as appropriate.
> 
> If you want to grab the branch and submit a merge proposal, the project
> is lp:bzr-migration-docs.
> 
> Ian C.

I have a couple of comments on the guide for Mercurial users. I should
probably send a patch, but I suck at writing docs, and I'm not going to
do it right now anyway.

* For more technically-inclined users, I think it helps to explain what
a Bazaar branch and repository *are*. Something like this, only more
eloquent: that a repo is basically a bag of revisions, and a branch is a
pointer to a specific revision, plus metadata like tags and the URL of
the parent branch. A Mercurial clone includes both, but the revisions
also all have to share a common ancestor.

* Unlike with Bazaar, "hg pull" does not automatically update the
working tree, unless you pass -u (or --update). Also, "hg pull -u" will
create a working tree if there is none. (Because in hg, "no working
tree" is exactly the same as "checkout of the null revision".)
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