r2026.04.19

[christian-schilling]

Changelog r2026.04.19

New Features

josh CLI (#1518)

A new josh command as a local alternative to using josh-proxy.
Josh remotes are stored in .josh files rather than git remote config. A josh remote subcommand
manages them.

josh publish (stacked changes) (#1916)

A new josh publish command for stacked-change workflows. It handles splitting a branch into
per-change refs, manages base refs for each change, creates/updates GitHub PRs automatically, and
marks non-bottom-of-stack PRs as drafts.

josh-filter

• josh-filter now accepts a commit SHA, the working tree (.), or the index (+) as input
  (Support commit SHA as input to josh-filter #1925, Support index and working tree as input for josh-filter #1942).
• josh-filter now returns the output SHA on stdout. Useful for scripting. (Print result sha from josh-filter #1635)
• josh-filter gained a roundtrip check mode to verify a filter can be applied and reversed back to
  the original. (Implement roundtrip check in josh-filter #1749)

New filter: :pin (#1573)

Prevents a path from being updated by new commits. The filtered tree retains the version from the
first parent.

New filter: :prune=trivial-merge (#1483)

Explicitly prunes merge commits whose tree is identical to the first parent, i.e., merges that
brought in no changes. Unlike the new default behavior of removing trivial merges introduced by
filtering (see Breaking Changes), this filter also prunes trivial merges that were already present
in the original history.

Stored filters (:+path/to/file) (#1601, #1611)

Filters can now be stored in .josh files within the repository tree and referenced via
:+path/to/file. Unlike workspaces, stored filters have no implicit subdir — the filter is applied
as-is. Stored filters can reference other stored filters (and workspaces can reference them too),
enabling composable filter libraries inside a repo. Workspaces cannot be referenced this way.

Filter syntax shorthands: :invert[f] and :<X>[f] (#1604)

:invert[:f] expands to the inverse of f.
:<X>[:f] is a scope shorthand that expands to :X:f:invert[:X].
Useful for composing filters that operate within a scoped context.

File filter supports renames (#1594)

The :file filter now supports renaming files.

:replace now supports inversion (#1480)

The :replace filter is now invertible.
Note that this does not undo replacements on the push path, but just enables use inside compose.

:message filter additions (#1589, #1680)

:message now accepts a regex pattern for rewriting commit messages and can read blob content from
the input tree to use in the commit message.

Filter meta options (#1710)

Filters now support a meta option syntax: :~(key="value")[filter].
They affect things like history shape and commit properties. Current meta options include:

• history="linear": linearize history (previously the standalone :linear filter); :linear
  is kept as a shorthand
• history="keep-trivial-merges": opt out of the new default behavior of removing trivial merges
  (see Breaking Changes)
• gpgsig="remove": strip GPG signatures from commits (previously the standalone :unsign
  filter); :unsign is kept as a shorthand
• gpgsig="norm-lf": normalize line endings in GPG signature headers to LF (backward
  compatibility option)

Experimental filters (Not enabled by default. Don't use in production!)

• :$path="content": inserts a blob with literal content at the given path. (Add blob insertion and treeid filter #1924)
• :#path[:f]: outputs the tree hash as a blob. (Add blob insertion and treeid filter #1924)
• :&path / :#path: reference and dereference trees or blobs by sha. (Add object ref/defref fiters #1938)
• :!path/to/script[:f]: like stored filters, but the .star file at the given path contains a
  Starlark script that computes the filter dynamically. (Change starlark filter syntax to :! #1935)

Retry with backoff in josh-proxy (#1895)

josh-proxy now retries transient upstream HTTP errors with exponential backoff, improving
reliability against unreliable upstreams.

ARM docker images

Release images are now published for arm64 in addition to amd64. (#1422) Images for all master
commits are also published to the GitHub Container Registry (ghcr.io).

Pluggable cache backends (#1558)

The filter cache now supports pluggable backends, making it possible to swap out the storage layer
for cache storage.

Distributed cache (#1559, #1957)

A new cache backend stores cache data inside a ref in the repository. This allows transferring a
warm cache between machines (e.g. via push/fetch), which is useful for seeding the cache in CI or
other environments where starting cold would be expensive. Currently only supported via the CLI,
not josh-proxy.

New josh cache build, josh cache push, and josh cache fetch subcommands manage the
distributed cache. josh cache build applies the configured filter to all already-fetched refs and
populates the local distributed cache. josh cache push and josh cache fetch transfer the cache
to/from a remote via ordinary git push/fetch.

josh clone, josh fetch, and josh pull automatically fetch the distributed cache from the
remote before filtering, avoiding a cold start.

---

Breaking Changes

Trivial merges removed by default (#1774)

Merge commits whose tree becomes identical to the first parent as a result of filtering are now
removed during history simplification. A meta option is available to restore the previous behavior
of keeping all trivial merges.

:rev filter syntax reworked; :from filter removed (#1785)

The :rev filter now uses explicit match operators (<, <=, ==) and a default wildcard (_)
instead of bare SHAs with the 000... wildcard. The :from filter has been removed; its use case
is covered by :rev with the _ default operator.

:join filter removed (#1615)

:join has been removed. It was a limited alternative to using --reverse/push.

Meta config support removed from josh-proxy (#1752)

The --meta URL parameter and associated clone-blocking/locking configuration (clone_locked_refs,
clone_blocked) have been removed from josh-proxy.

josh-ui (web UI) removed (#1956)

The /ui endpoint no longer exists. The josh-ui component has been removed from the project.

Cache moved to .git/josh/cache (#1787)

The local sled cache is now stored at .git/josh/cache instead of .git/josh.

---

Performance Improvements

Complex workspace/stored filter graphs (#1959)

The algorithm for selecting which missing filter to compute next now uses nesting level. This
prevents an exponential blowup in the number of "missing" entries on graphs involving workspaces
with many filters.

Filter optimizer: Prefix sort fixed and optimized (#1469)

The prefix sort used a comparison function that did not satisfy total ordering, causing panics after
a Rust update. The sort was rewritten to order entries alphabetically while preserving the relative
order of filters that share a prefix as input or output directory. Additionally fixed quadratic
complexity when composing many prefix entries, with further micro-optimizations: faster hash,
eliminated redundant hashing.

Workspace cache overlocking fixed (#1482)

The lock was held during workspace .josh file parsing, serializing concurrent requests. The lock
scope has been narrowed.

is_ancestor_of early exit (#1729)

A new sequence number is assigned to each commit during traversal. Sequence numbers take the
maximum over all parents, guaranteeing monotonicity and enabling earlier termination during
ancestry checks.

find_unapply_base early exit (#1665)

find_unapply_base now exits early once the base is found.

Serve /info/refs inside josh-proxy (#1735)

josh-proxy now serves /info/refs directly instead of spawning git http-backend. Previously,
refs had to be written into a namespace directory so that http-backend could read them back —
a bottleneck that scaled poorly with large numbers of branches. Serving refs directly cuts push
latency substantially (e.g. ~33% faster on repos with ~600 branches).

---

Bug Fixes

• chain(prefix(a/b), subdir(a)) optimizer produced wrong results: the filter optimizer had
  a bug when chaining a prefix with a subdir that partially overlapped. (Fix chain(prefix(a/b),subdir(a)) #1529)
• Workspace discovery broken when workspace.josh is at repo root: produced invalid filter
  syntax. (Fix workspace discovery #1470)
• :message filter placed in wrong position by optimizer (Fix message filter being put in wrong position by optimizer #1648)
• Auth cache could grow without bound: the HTTP-password-keyed auth cache is now bounded in
  size. (Limit size of auth cache keyed by HTTP password #1412)
• SSH container stopped accepting connections after ~16 clones: the MaxStartups option in
  the container's sshd config was too low; it has been removed so sshd uses its default. (Remove SSH max startups option #1773)
• Stacked push: changes without a Change-Id were not skipped (Skip changes without id in stacked push #1584)
• Stacked push: a failure on one ref aborted remaining refs: each ref is now pushed
  independently. (Keep pushing other refs if one fails in split push #1830)

---

This discussion was created from the release r2026.04.19.