Every version, and what it changed for you.

A file's own history, and a second storage engine.

Before you upgrade — The first run after upgrading indexes your tree from scratch, on both engines. Incremental updates resume afterwards.

• NewArchis keeps the revisions of a file it has indexed, shows what changed between any two of them, and can put one back. This is the edit loop between commits, which is the window git does not have. A revert costs a path and a number instead of the whole file re-emitted as a patch, and output tokens are the expensive ones — and a revert can itself be reverted, because restoring appends to the history rather than rewinding it.
• NewA second storage engine, chosen per repository. Measured across twelve repositories from 0.7 MiB to 410 MiB it holds an index in 0.22× the disk, answers "who calls this" in 0.04× the time and applies a hundred-file edit in 0.02×. It keeps no file revisions, and says so with the reason rather than failing the request — which is why the choice is yours and per repository.
• NewSeveral git branches in one index, so switching branch moves a pointer instead of reindexing — measured at 3 to 47 ms. Off by default: indexing every active branch on a large repository turns a ninety-second index into five minutes for somebody who asked for neither. Your working tree is never touched.
• Newchi.json — a repository's own settings, in its .chi directory. Created with defaults when absent and never rewritten when present, including when it is broken: a trailing comma is somebody's edit, and replacing the file to "recover" turns a mistake anyone could fix into lost work.
• FixedA file whose modification time moved backwards was served from the previous index — true of every tool that restores a timestamp rather than setting it to now: checking out an earlier revision, rsync -a, tar -x, a restored backup. The bytes were different, nothing had failed, and the old answer came back with no warning.
• FixedTwo files whose module roots share a name lost one of their imports, and re-indexing either could delete an edge the other still needed. One large public repository was missing 1,016 of its 23,108 imports.
• FixedYour repository's prose — README, changelog, design notes — was missing from indexes built on the new engine.