cache.hierarchicalPath: store cache files as $directory/a/b/c.cc.blob to
work around NAME_MAX limitation.
cache.retainInMemory: after this number of loads, keep a copy of file
index in memory. If set to 1, it avoids cache corruption if the index
file is changed after the initial load, which may happen if several
language clients open the same project and share the same cache
directory.
Also rename cacheDirectory cacheFormat to cache.{directory,format}
* In the "initialized" callback, send client/registerCapability with DidChangeWatchedFilesRegistrationOptions
* In workspace/didChangeWatchedFiles callback, call pipeline::Index
* In pipeline::Index, add a `deleted` status
In completion, underscore prefixed builtin macros may be annoying when the first type character is not an underscore.
When `strict` is true, `Match` enforces the first characters should be loosely of the same category.
* WorkingFiles::files : vector -> unordered_map
* Add timestamp to WorkingFile
* Rename "comp-preload" thread to "preamble"
* Rename CompletionManager to SemaManager as it is used by "diag" "comp" "preamble"
* Rename clang_complete.* to sema_manager.*
* Merge SemaManager::{preloads,sessions}
* Add initialization option session.maxNum
* In DiagnosticMain, if an included file was modified, cancel the DiagTask and create a PreambleTask instead. The task sets `from_diag` so as to trigger immediate DiagTask after the preamble is built.
