[PATCH V3] destutil: choose non-closed branch head at first (BC)

[Matt Mackall]

On Tue, 2016-03-08 at 19:59 +0900, FUJIWARA Katsunori wrote:
> # HG changeset patch
> # User FUJIWARA Katsunori <foozy at lares.dti.ne.jp>
> # Date 1457288059 -32400
> #      Mon Mar 07 03:14:19 2016 +0900
> # Node ID 4c53d1402e9d641f9b9f99ac6114e1f13e51fc45
> # Parent  ffd3ac07b1d79dda7f57bd826208fdaf92a76717
> destutil: choose non-closed branch head at first (BC)
> 
> Before this patch, destupdate() returns the tipmost (descendant)
> branch head regardless of closed or not. But updating to closed branch
> head isn't reasonable for ordinary workflow, because:
> 
>   - "hg heads" doesn't show closed heads (= updated parent itself) by
>     default
> 
>   - subsequent committing on it re-opens closed branch
> 
>     even if inactivation of closed head is needed, update destination
>     isn't it, because it should be merged into to another branch in
>     such case.
> 
> This patch chooses non-closed descendant branch head as default update
> destination at first. If all descendant branch heads are closed,
> destupdate() returns the tipmost closed branch head.
> 
> For simplicity, this patch chooses adding _destupdatebranchfallback()
> instead largely changing _destupdatebranch().
> 
> This patch changes not only normal lookup code path, but also "no
> default branch" code path, for consistency.

A couple notes here:

- test-convert-mtn.t needs updating

> +  updated to a closed branch head, because all descendant heads are closed.
> +  beware of re-opening closed head by subsequent commit here.
> +  1 other heads for branch "default"

This is a really long message and not really in our normal format. We should be
aiming for:

 one line description of the problem with no period
 (a suggestion about how to move forward or get more info)

Something like:

 no open branch heads, updating to a closed head
 (committing will reopen the branch)

We also might consider making it a warning.

-- 
Mathematics is the supreme nostalgia of our time.