[PATCH 0 of 3] An attept at branch closing

[Matt Mackall]

On Sat, 2008-10-04 at 16:28 -0400, John Mulligan wrote:
> I have a Mercurial repository that was converted from CVS and has a lot of 
> branches I don't want to see, but some that I do. This motivated my to try
> and implement a mechanism for (the oft requested?) named branch closing.
> I haven't heard about much activity on the subject lately, so I hope 
> I'm not stepping on anyones toes who may have also been working on this.
> 
> I took my lead from this post of Matt's:
>   http://selenic.com/pipermail/mercurial-devel/2008-March/005144.html
> 
> I added a --close-branch option to commit. This adds a extra 'close' 
> attribute to the changeset makes the branch dissapear from heads 
> and branches. To revive a branch you must hg up to the rev number
> and make a commit.
> 
> I have also added tests for the branch closing.
> 
> Please feel free beat up on this. :-)
> 
> 
> Open Issues
> ===========
> 
>  * After `hg commit --close-branch -m "close messy branch"` what
>    branch should the working dir be on? Currently the parent will be
>    the cset with the close marker, and making a change and committing
>    will re-open the branch!

An excellent point. But at the same time, it's completely 'natural' once
you understand the Mercurial basics.

>  * Should the log print something like:
>     
>       changeset:   8:7db20c52f570
>       branch:      b (closed)            
>       parent:      4:aee39cd168d0
>       user:        test          
>       date:        Thu Jan 01 00:00:07 1970 +0000
>       summary:     zap b branch

That might confuse existing parsers.

>  * What should happen if the user tries to start a new branch with the
>    same name as a closed one? Right now, nothing fails, you just end up
>    with two heads that both consider themselves on the same branch.

I took a stab at writing this code earlier and the fun I ran into was
primarily in handling the branch cache. Imagine this tree:

A1-A2-A3-A4-B1-B2-B3
     \
      A5-A6-A9 (tip)
        \
         A7-A8

If we close A9 by adding a close at A10, the A branch is still open
because it has an open head at A8. The head at A4 is inactive by virtue
of having a child on a different branch.

And that means as we're building the cache, we have to remember A8 even
when it gets overridden by A9, because A10 might come along and make A8
the branch tip again.

-- 
Mathematics is the supreme nostalgia of our time.