[PATCH 1 of 1] ( take 4 ) change tag computation to avoid surprises in case of multiple heads

[Matt Mackall]

On Sat, Jan 13, 2007 at 09:11:09PM +0100, Georg-W. Koltermann wrote:
> # HG changeset patch
> # User Georg.Koltermann at mscsoftware.com
> # Date 1168718842 -3600
> # Node ID 93ab992f68c4b0372801a2396de4276a13211542
> # Parent  27230c29bfec36d5540fbe1c976810aefecfd1d2
> FEATUREFIX: Change tag computation so that obsoleted tag lines (those lines in a tags file that are
> superseded by subsequent lines of the same tag) are ignored.
> 
> Previously for any given tag the last entry in the tipmost tags file would win.  This caused
> considerable surprises when a new tip was created off a historic version containing an
> older .tags file.
> 
> With this change, lines that are superseded by newer entries in .tags files (called
> obsoleted lines) are ignored in the process of tag computation. So creating a new
> tip off a historic version will only result in exposing a new obsoleted tag entry which
> is ignored, so having no effect on the final tag value.
> 
> (take 4 of the patch, supports un-obsoletion, + bugfix)

I think this fails on the following case:

tip   other
a     a
b     b
a     a 
b     b
      a

We look at tip last and see that b obsoletes a.

Looking for a fix.

-- 
Mathematics is the supreme nostalgia of our time.