What make rebase_to_dest_parent a good candidate for jj_lib::rewrite module:
- It is used both in obslog and interdiff. It's a sign that it may be moved to a lower layer
- CommandError is returned by converting from TreeMergeError. Not explicitly.
- It only use jj_lib::rewrite fonctions.
This will make it a little faster to update the working copy at Google
once we've made `MergedTree::diff_stream()` fetch trees
concurrently. (It only makes it a little faster because we still fetch
files serially.)
I'm going to implement a `Stream`-based version optimized for
high-latency (RPC-based) commit backends. So far, that implementation
is about 20% slower in the Linux repo when running `jj diff
--ignore-working-copy -s --from v5.0 --to v6.0`. I think that's almost
only because the algorithm is different, not because it's async per
se.
This commit adds a `Stream`-based version of `MergedTree::diff()` that
just wraps the regular iterator in stream. I updated `jj diff` to use
it. I couldn't measure any difference on the command above in the
Linux repo. I think that means we can safely use the same
`Stream`-based interface regardless of backend, even if we end up
needing two different implementations of the `Stream`. We would then
be using the wrapped iterator from this commit for local backends, and
the new implementation for remote backends. But ideally we can make
the remote-friendly implementation fast enough that we don't need two
implementations.
During the transition to using more async code, I keep running into
https://github.com/rust-lang/futures-rs/issues/2090. Right now, I want
to convert `MergedTree::diff()` into a `Stream`. I don't want to
update all call sites at once, so instead I'm adding a
`MergedTree::diff_stream()` method, which just wraps
`MergedTree::diff()` in a `Stream. However, since the iterator is
synchronous, it needs to block on the async `Backend::read_tree()`
calls. If we then also block on the `Stream` in the CLI, we run into
the panic.
We had similar code in two places for restoring paths from one tree to
another. Let's reuse it instead.
I put the new function in the `rewrite` module. I'm not sure if that's
right place. Maybe it belongs in `tree`?
Since gix::Repository::config_snapshot() borrows the repo instance, it has to
be allocated in caller's stack. That's why GitBackend::git_config() is removed.
My gut feeling is that gitoxide aims to be more transparent than libgit2. We'll
need to know more about the underlying Git data model.
Random comments on gix API:
* gix::Repository provides API similar to git2::Repository, but has less
"convenient" functions. For example, we need to use .find_object() +
.try_to/into_<kind>() instead of .find_<kind>().
* gix::Object, Blob, etc. own raw data as bytes. gix::object and gix::objs
types provide high-level views on such data.
* Tree building is pretty low-level compared to git2.
* gix leverages bstr (i.e. bytes) extensively.
It's probably not difficult to migrate git::import/export_refs(). It might
help eliminate the startup overhead of libssl initialization. The gix-based
GitBackend appears to be a bit faster, but that wouldn't practically matter.
#2316
Otherwise, the initialized repo could have a different work-dir path than the
load()-ed one. libgit2 appears to do some normalization somewhere, but gix
won't.
I've enabled the "index" component from the "basic" feature set, which would
be needed to implement colocated repo functionality. The doc suggests that
a library shouldn't activate "max-performance-safe", but our crate is also
an application so it would be okay to enable the feature. We'll need "parallel"
anyway to make GitBackend Sync.
https://docs.rs/gix/latest/gix/#feature-flags
This avoids https://github.com/rust-lang/futures-rs/issues/2090. I
don't think we need to worry about reading legacy conflicts
asynchronously - async is really only useful for Google's backend
right now, and we don't use the legacy format at Google. In
particular, I don't want `MergedTree::value()` to have to be async.
I want to fix error propagation before I start using async in this
code. This makes the diff iterator propagate errors from reading tree
objects.
Errors include the path and don't stop the iteration. The idea is that
we should be able to show the user an error inline in diff output if
we failed to read a tree. That's going to be especially useful for
backends that can return `BackendError::AccessDenied`. That error
variant doesn't yet exist, but I plan to add it, and use it in
Google's internal backend.
Reasons to introduce this alias:
* Reduces complexity of a type, to silence Clippy warnings in the
future if we use this type as a type parameter
* The type is used quite frequently, so it makes sense to have a name
for it
* It's easier to visually scan for the end of the type when you don't
have to match opening and closing angle brackets
I'm going to add `MergedTreeValue` as an alias for
`Merge<Option<TreeValue>>`, but we already have a type by that name in
`merged_tree`. This patch renames it away, to make room for the new
alias. I used `MergedTreeVal` for this borrowing version to be a bit
like how `str` is a borrowed version of `String`.
Since "jj git fetch --branch" supports glob patterns, users would expect that
"jj git push --branch glob:.." also works.
The error handling bits are copied from "branch" sub commands. We might want to
extract it to a common helper function, but I haven't figured out a reasonable
boundary point yet.
AFAICT, all callers of `Merge::to_file_merge()` are already well
prepared for working with executable files. It's called from these
places:
* `local_working_copy.rs`: Materialized conflicts are correctly
updated using `Merge::with_new_file_ids()`.
* `merge_tools/`: Same as above.
* `cmd_cat()`: We already ignore the executable bit when we print
non-conflicted files, so it makes sense to also ignore it for
conflicted files.
* `git_diff_part()`: We print all conflicts with mode "100644" (the
mode for regular files). Maybe it's best to use "100755" for
conflicts that are unambiguously executable, or maybe it's better to
use a fake mode like "000000" for all conflicts. Either way, the
current behavior seems fine.
* `diff_content()`: We use the diff content in various diff
formats. We could add more detail about the executable bits in some
of them, but I think the current output is fine. For example,
instead of our current "Created conflict in my-file", we could say
"Created conflict in executable file my-file" or "Created conflict
in ambiguously executable file my-file". That's getting verbose,
though.
So, I think all we need to do is to make `Merge::to_file_merge()` not
require its inputs to be non-executable.
Closes#1279.
Resolves states are most common and the current format is pretty
verbose. Let's print it as if `Merge` were an enum with `Resolved` and
`Conflicted` variants instead.
Since local/remote branches are now of different types, it doesn't make much
sense to dispatch merging through RefName. Let's add merge_<kind>() methods
instead.
MutableRepo handles merging of the other kind of refs internally, and the
merge function is short enough to inline. I also removed early returns since
most callers provide non-identical ref targets, and merge_ref_targets() should
be cheap if the inputs can be trivially merged.
This partially reverts the change in 30fb7995c2 "view: make local/remote
branches iterator yield RemoteRef instead of RefTarget." As I'm going to add
diff function for RemoteRef pairs, we'll need a generic version of merge-join
iterator anyway.
We need to let async-ness propagate up from the backend because
`block_on()` doesn't like to be called recursively. The conflict
materialization code is a good place to make async because it doesn't
depends on anything that isn't already async-ready.
It seems we'll end up using `block_on()` quite a bit, at least until
we're done transitioning to async, and the function name doesn't
conflict with anything else, so let's always import it when we need
it.
