Make pull.without-history work for Share project branches

[ChrisPenner]

Overview

Pulling without history (i.e. a squashed version of a branch) is handy when you just need the code, but won't be contributing back. E.g. installing an executable.

Typically users will simply pull a release, which are already squashed, but the cloud team has requested the ability to do this with their main branch to speed up CI significantly.

This makes pull.without-history use a server-side squash rather than a local squash after pull so we can get away with pulling significantly less data and speed things up. Currently this is implemented only for project branches, not loose-code.

Merge and deploy the server side first:
See server-side: https://github.com/unisoncomputing/enlil/pull/322

myproj/main> history

  Note: The most recent namespace hash is immediately below this message.

  ⊙ 1. #jgeoqlvtoe

    + Adds / updates:

      x1 y

    = Copies:

      Original name New name(s)
      x3            x1

  ⊙ 2. #5kefseq9bm

    > Moves:

      Original name New name
      x2            x3

  ⊙ 3. #s88t06ld0p

    > Moves:

      Original name New name
      x1            x2

  ⊙ 4. #du8rbf12ei

    + Adds / updates:

      x1

  □ 5. #9gvcfnpaj2 (start of history)

myproj/main> push @test/myproj

  @test/myproj/main on http://localhost:5424 is already up-to-date.

myproj/main> cd .
.> pull.without-history @test/myproj squashed

  ✅

  Successfully updated squashed from @test/myproj/main.

.> cd squashed
.squashed> history

  Note: The most recent namespace hash is immediately below this message.



  □ 1. #ar8hiee861 (start of history)

.squashed> ls

  1. builtin/ (622 terms, 88 types)
  2. x1       (Nat)
  3. x3       (Nat)
  4. y        (Nat)

.squashed>

Implementation notes

When running pull.without-history to pull a remote branch, use the new includeSquashed flag to ask Share to include the squashed causal hash in the response (and to ensure it's available to download). Then use that squashed hash when downloading instead of the branch head.

Interesting/controversial decisions

Optionally this could've been a new endpoint, but I think it's both sensible and simple to adapt the existing get branch endpoint.

Note: The squashed causal hash is always included on release downloads since those are already squashed, but it's the same as the branch-head in that case.

Test coverage

See the UCM session captured above.

Loose ends

Need to deploy the Share side before merging this.

[ChrisPenner]

Looks like at least one of the transcripts does a pull.without-history and is failing because the share portion hasn't been deployed yet. Just a good reminder to deploy the share part first, then that should clear up 😄