This PR changes how base texts are managed by the `buffer_diff` crate,
to enable keeping two diff entities alive that share the same base text
buffer entity. Previously, each diff owned its own base text buffer and
edited it when calling `BufferDiff::set_snapshot`, so the only way to
reuse the same base text between two diffs was to have two independent
buffers for it, which is pretty inefficient.
After this PR, each diff still has a base text buffer, but
`set_snapshot` doesn't edit it. Instead, that responsibility moves into
the caller. For updating the base text buffer, this PR also introduces a
new pair of APIs, `Buffer::snapshot_with_edits` and
`Buffer::fast_forward`, which allow us to move the parsing of the new
base text into the background and then install the new syntax tree
synchronously on the foreground.
The git store uses the low-level APIs `set_snapshot` and `fast_forward`
directly, and manages the head text and index text buffers itself
(garbage-collecting them when they're no longer needed); this enables
adding an `open_staged_diff` API which returns a diff between the
managed index buffer and the managed head buffer (the latter is also
used for the uncommitted diff's base text). Other downstreams don't need
to reuse a base text buffer, and those have been migrated to use the
high-level `set_base_text` API, which now calls `set_snapshot` and
`fast_forward` internally, with a guard to prevent concurrent updates.
Another change worthy of note is that we now always diff the old base
text with the new base text to create `snapshot_with_edits`.
There are also some incidental bug fixes:
- Fixed an issue where a dangling weak unstaged diff could stick around
in the git store forever
- Restored the `IndexMatchesHead` optimization that had become
inoperative in the remote case
- Fixed a crash in the multibuffer due to the handling of
`BufferDiffEvent::LanguageChanged`, which could cause the multibuffer to
have transforms that were inconsistent with the diff base text.
Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Closes ZED-81P
Release Notes:
- Fixed a rare crash that could occur while using the uncommitted diff.
---------
Co-authored-by: Ben Kunkle <ben@zed.dev>
Co-authored-by: Anthony Eid <hello@anthonyeid.me>
Remove the BreadcrumbText struct from workspace and use the existing
HighlightedText struct from the language crate instead. The per-segment
font field is replaced by returning an optional Font alongside the
segments from the breadcrumbs() method, since the font was always
uniform across all segments of a given item.
Release Notes:
- N/A *or* Added/Fixed/Improved ...
Replaces a bunch of `impl FnMut` parameters with `&mut dyn FnMut` for
functions where this is the sole generic parameter.
Release Notes:
- N/A *or* Added/Fixed/Improved ...
Currently we always compute breadcrumbs and sticky headers on every
editor paint which is not cheap to do especially in bigger files, moving
this off to be computed on event handling where they change and then
caching them can save serveral milliseconds per render in bigger files.
This also puts matching brackets refreshing and document highlights on a
background task, as this tends to block the main task for prolonged time
as well.
Release Notes:
- N/A *or* Added/Fixed/Improved ...
This branch:
1. teaches `--diff `command line option to to recurse into folders if
provided.
2. Adds a `MultiDiffView` that shows _all_ changed files in a single,
scrollable view.
This is necessary to provide a smooth user experience for `jj` and Zed
users who wish to use Zed as their jj difftool.
I'm not fully sure how this change interacts with
https://github.com/zed-industries/zed/pull/44936, or what plans y'all
have in mind.
Here's a screenshot of the resulting behavior:
<img width="1090" height="950" alt="Screenshot 2025-12-17 at 9 10 52 AM"
src="https://github.com/user-attachments/assets/8efd09b4-974f-4059-9f94-539c484c6d4a"
/>
I setup zed to handle jj diffs by adding the following to my jj config:
```toml
[aliases]
zdiff = ["diff", "--tool", "zed"]
[merge-tools.zed]
program = "/Users/dbarsky/Developer/zed/target/debug/cli"
# omit diff-invocation-mode to keep the default (JJ passes two dirs)
diff-args = [
"--zed", "/Users/dbarsky/Developer/zed/target/debug/zed",
"--wait",
"--new",
"--diff",
"$left",
"$right",
]
```
Release Notes:
- `--diff`, if provided with folders instead of files, will recurse into
those directories.
- Added a `MultiDiffView`, which will show all changed files within a
single, scrollable view.
**AI Disclosure**: Pretty much all of this code was written using Codex
with GPT-5.1-Codex. I edited by hand and tested this.
---------
Co-authored-by: Lukas Wirth <lukas@zed.dev>
