[PATCH] bookmarks: do not move merged bookmarks (issue1877)

[Matt Mackall]

On Fri, 2011-03-25 at 16:05 +0100, Martin Geisler wrote:
> Matt Mackall <mpm at selenic.com> writes:
> 
> > On Fri, 2011-03-25 at 14:36 +0100, Oben Sonne wrote:
> >> # HG changeset patch
> >> # User Oben Sonne <obensonne at googlemail.com>
> >> # Date 1301058026 -3600
> >> # Branch stable
> >> # Node ID 4e046b57caf4f2e282bddbb93c7e192ae00788ba
> >> # Parent  913c2c66a555934cab9bcdac3412703256f9cdf2
> >> bookmarks: do not move merged bookmarks (issue1877)
> >
> > An excellent first patch submission. But we generally try to avoid
> > adding a whole new test script to add a simple test. If every bugfix
> > needed to create its own trivial repo to run its test on, the test suite
> > would take an hour to to run. Instead, try to find somewhere else in the
> > bookmark tests that is already creating a repo with branches and test
> > merging those.
> >
> > I'm not entirely sure if this is the right behavior. Merges are
> > generally symmetric. Currently the only exception to this is branch
> > names, and perhaps this is similar enough to that case that it makes
> > sense, but I'd like to see an actual argument for it.
> 
> One argument could be that leaving the bookmark in place makes pulling
> bookmarks easier in the future. That is, when I pull in a branch with
> bookmark X from you and merge it into my own line of development, then I
> end up with
> 
>    ... o --- o --- M
>           \       /
>            o --- o
>                  X
> 
> Some time later I pull from you and pull your new X bookmark:
> 
>    ... o --- o --- M
>           \       /
>            o --- o --- o --- o
>                              X
> 
> If the X bookmark had moved to M when I merged, then I believe the
> bookmark code would not let is jump back to your branch tip since the
> tip is not a descendent of M.

Yes, but what I'm looking for is an argument that explains why we should
_break the symmetry_. In other words, I can turn your graphs
upside-down, doesn't that tell us we should do the opposite of this
patch?


-- 
Mathematics is the supreme nostalgia of our time.