Change management and regression errors.

[Michael McClary <michael>]

I just realized where some of the reappearing code might be coming from.

I've noticed people file in in each other's changes between releases,
accepting verbal assurances about what is affected, rather than testing
this with a tool.

If the filein contains a minor change to something you've just hacked, your
changes are lost and you don't know it.

(I have thought of a couple ways to deal with this, but want to check with
Ravi about whether any are already supported or could be added without
major hacking.  My impression is that the only available tool is "browse
conflicts" and that it isn't used often because it's slow.)

	michael