Taskcluster-taskgraph

Fixed

- Bug preventing use of custom `group_by` functions with `from_deps` transforms

Added

- New `from_deps` transforms for creating follow-up tasks

Fixed

- Parallel generation (via multiple params) returns non-zero if one fails

Fixed

- Regression around make index transform running out of order
- Counted `if-dependencies` and `soft-dependencies` towards dependency limit check
- Error messaging when Docker is stopped
- Error messaging when invalid non-existent dependencies are added
- Command line exception when branch name contains a `/`
- Abort long running Git clone / fetch when transfer is too slow

Added

- New `default` loader which implicitly uses the `job` and `task` transforms
- Support for a custom command to invoke `run-task` in the `job.run_task` transforms
- Can omit object (default: `transforms`) when listing transforms in a kind config
- Ability to specify `treeherder: true` which will auto-populate Treeherder metadata
- Added `index-path-regexes` key to `config.yml` which can be used with `make_index_task` morph

Fixed

- Stop injecting `docker-image` tasks when DONTBUILD is used in commit message

Changed

- `fetch-content` and `robustcheckout` time out on idle http connections

Removed

- Support for python 3.6

Changed

- Updated github ssh host key (per https://github.blog/2023-03-23-we-updated-our-rsa-ssh-host-key/)