D4490: wireprotov2: define and implement "filedata" command

[indygreg (Gregory Szorc)]

indygreg added a comment.


  In https://phab.mercurial-scm.org/D4490#69457, @durin42 wrote:
  
  > Oh, one more thing: I think this, as-stated, will make it at best challenging to have ACLed branches: we'd have to, on the server, walk the linknodes and see if the client was authorized to see any branch(es) that contain the node.
  >
  > That's probably okayer for us than it was for git (since we have linkrevs at least), but it's still worth considering.
  
  
  First, totally agree with you about wire protocol / command overhead. I plan to add bulk querying APIs later.
  
  Also, I wasn't aware of the ACL'd branches requirement. I'll have to think of ways to handle that. It may involve the server advertising the available mechanisms for requesting file data (e.g. "request by file node" and "request by changeset node") and the server not allowing certain modes. But that example would undercut raw data access. So maybe it gets advertised as a server preference. Or maybe we end up not doing the "request by file node" path in the common case and the server overhead isn't a problem in practice.
  
  I'll keep this use case in mind when writing future commits.

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REVISION DETAIL
  https://phab.mercurial-scm.org/D4490

To: indygreg, #hg-reviewers, durin42
Cc: durin42, mercurial-devel