D21668 should improve this behavior, although it's not an ideal or complete fix.

This is now in stable; presuming it works until evidence to the contrary emerges.

The modern differential.revision.search API returns the repository for the revision.

I'm likely to break the paths constraint for frozen API method differential.query. This was added by D2788 as a Facebook-specific patch with no rationale that I can dig up, and the author didn't have any related changes from around that time.

Yep, that's more constraints.

• There is no way to pull custom field values with *.search. See above.
  • There is no way to edit non-custom field values with *.edit. The underlying transactions haven't been modularized yet; they should be, then EditEngine should get appropriate EditField definitions.
  • There's no way to identify which custom fields can be edited. This overlaps with T13248, but is also a Conduit API Console UI problem. The web UI should have some way to inspect parameter variations per object subtype for available subtypes.
    • As a workaround, you can try to edit an invalid field. The error message will identify valid fields.
  • There's no way to create steps with *.edit because you can't specify a step type. See T13449 for a general variation of the "type is required to initialize objects" problem.

HarbormasterBuildStepCoreCustomField emits no fields if a BuildStep has no attached Implementation object. This dates from D15352 and is conceptually reasonable ("don't crash if a build step exists but the implementation no longer does") but should probably be represented differently (e.g., an explicit "InvalidImplementation").

One possible improvement remains here: in streaming mode, HTTPSFuture will not "Accept-Encoding: gzip" and can not inflate responses. Today, this only applies to arc download.

There's also one minor related concern in PHI1638 that I want to take care of here, since it's adjacent.

In fairness, "SetInputFilter DEFLATE" is documented as uniquely opinionated, if you catch this box and read between the lines a little bit:

A grand aventure in PHI1679 led to identifying the Apache "SetInputFilter DEFLATE" directive as a problem with implementing compression.

"FutureGraph" is dead. Long live "HardpointEngine".