for discussion None vs null: vs current:

[Martin Pool]

On 19 Jul 2006, Robert Collins <robertc at robertcollins.net> wrote:

> EMPTY_REVISION - 'empty:'

This needs to represent both value (contains nothing) and identity
(ultimate ancestor).  "empty" might suggest it just happens to be empty?
The word "root" is used for too many other things but how about
"origin:"?  I could live with "empty:" though.

> NULL_REVISION - 'null:'

And what will this actually do?

> CURRENT_TREE_REVISION - 'current:'

OK

> None aka NOT_A_REVISION - ':'

Let's make it "not_a_revision:" or something then, unless there's any
compelling reason it needs a one-character name?

> open discussion points:
>  * should we use other delimiters than :.
>  * does NOT_A_REVISION make sense?

Only if you can think of a plausible case where it will occur?  Maybe
having decided on it we should add it as a comment to revision.py but
not use it yet.

I think reserving revision ids ending with : for this is fine, and in
general treating the bit before the first colon as a namespace that
needs to be coordinated is also fine.

-- 
Martin