pull and merge use case

[Martin Pool]

On 21 Nov 2005, James Blackwell <jblack at merconline.com> wrote:

> > Is there a use case where if the branches have diverged, you would
> > rather not merge.

That is, when or how would it be harmful to have pull automatically
merge?

A few cases

 - You have uncommitted changes which (as you say) will now be mixed in
   with the merge results.  I suppose we could special case this by
   having it refuse to merge if there are uncommitted changes (as it
   currently does in merge).

 - Sometimes pull must be followed by a commit; sometimes it shouldn't
   be.  This seems badly inconsistent to me.  But perhaps it's the
   lesser evil.

I can definitely see the attraction of having just one command; but also
the downside of one command with two very different behaviours.

> > I suppose User A's 'pull to update to latest' should switch the local
> > branch, and allow them to commit normally. I was just concerned that
> > when they go to commit, they would actually get DivergedBranches, rather
> > than OutOfDate. Because the revision-history has changed because of the
> > switch.
> 
> This whole thing seems to strike me as inventory reordering. Its the same
> stuff, just recorded in a different order in the inventory. Though I can
> imagine log output changing and unusual merges (for non-head revisions)
> potentially failing, why would a user otherwise care?

I think you mean revision-history reordering, not inventory reordering.
The inventory is the 'space' dimension, a list of what files and other
objects are present in any given revision.

The ordering of revisions on a straight line will never change: if A is
a parent of B it will always be so.  However the graph may pivot so that
revisions which were previously on the mainline are now off to the side.

I think we've all agreed that that pivoting is worthwhile.

>    * Puts local commits at the end of the invenotry.

Our model of commits doesn't let you reparent them; that should be done
in a higher-level quilt-like tool.

-- 
Martin
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