[Monotone-devel] RFC: 'suspend' certs

[William Uther]

Hi all,

  I'm busy scratching mtn itches.  Another on my list is that I tend  
to refrain from using branches as very lightweight objects because  
they never go away.  Now, the mythical policy branches were touted as  
a solution to this, but I must admit I don't have a clear idea of how  
they're supposed to work...  (BTW, I'm in the Bay area at the  
moment.  If someone is around who understands policy branches and  
wants to chat about them, drop me an email.)

  Anyway, I have another proposed solution.  It is a 'suspend'  
cert.  It looks the same as a 'branch' cert in that it contains the  
name of a branch.  The effect of a 'suspend' cert is to remove that  
revision from any list of heads for that branch.  If all the heads of  
a branch are suspended, then the branch no longer appears in "mtn ls  
branches".

  The meaning of suspend is not "this is a bad revision": we already  
have test failure for that.  The meaning is "I don't want mtn to  
bother me with this revision".

  We could use other synonyms for suspend: "discontinue",  
"terminate", "cease", "close", "yield", "shelve", "end", "finish",  
"conclude", "abandon", "vanish", "obviate", "debar", "inactivate",  
"desist"... but I'll go with suspend unless there is an outcry.   
( http://en.wikipedia.org/wiki/Color_of_the_bikeshed )

  Notes:
    - A suspend cert does not stop anyone from making descendants of  
the revision, and they'll appear on lists of heads just as normal.
    - A suspend cert does stop merge from trying to merge the  
revision by default.  (I'm looking at putting the filter in  
project_t::get_branch_list(), project_t::get_branch_heads() and  
pick_update_candidates())
    - A suspend cert and update interact in a somewhat complex  
manner.  If all update candidates are suspended then they're all  
considered.  If some update candidates are not suspended, then all  
the suspended candidates are removed.

Thoughts, comments?

Will         :-}