This release supports (and requires) HHVM 3.28

New Features

add migration to convert PHP stdlib to the HSL
add add-you-type linting in supported editors
better diff previews for auto-fixing linters when linting from CLI
all lint autofixes are now available within supported editors; previously, all lint errors were exposed, but only AST-based lint errors could be fixed within editors

API Changes

EditableList is now EditableList<T as EditableNode>
methods that return A|B|Missing now return ?EditableNode; this is to increase consistency, as A|Missing returns ?A
getFile() now returns a File object, including both a path and content. Linters must operate on the content exposed here for as-you-type linting to work correctly
fixLintErrors() has been removed, replaced with getFixedFile(); getFixedFile() must not edit the file on disk, but should return a new File object with modification applied
getPrettyTextforNode() no longer takes a $context parameter; this is rarely used, and requires major usability compromises to the rest of the API. Implementations should store context themselves, or re-calculate it here.
FixableLintError has been removed: any LintError is fixable if the linter is an AutoFixingLinter
LSPAutoFixingLinter has been removed; all AutoFixingLinters are now fixable via LSP; this is built on top of getFixedFile() and getTitleForFix()
Merged BaseASTLintError and ASTLintError into ASTLintError: this distinction was to provide a simpler API for common cases, however the removal of FixableLintError and $context removed all differences.

removed --io-log-prefix option; the situations where it was useful are better served by in-editor logging, or using a wrapper along the lines of tee stdin.log | path/to/real/hhast-lint "$@" 2>stderr.log | tee stdout.log, as the IO logs only contain output that goes through certain abstractions, rather than all process output.
added HHAST_LSP_DEBUG environment variable, which prints various state changes to stderr