Fixes #3968

Fixes #3975

Now, it matches `materialize_merge_result`

We don't have to test emptiness of contents between unchanged regions.

This seems more consistent as we have a terminal range at the end.

This isn't important, but I'm going to add another empty range at the start,
and it's easier if the modification of regions is scoped.

The Ord implementation didn't conform to Eq (which compares "self.others"
literally), and we don't need Ord to insert non-overlapping ranges before the
current range.

fixes martinvonz/jj#4207

The default clap's help command doesn't have the ability to accept flags
(e.g --no-pager). The recommended way[1] to solve this is to manually
implement it.

[1]: https://github.com/clap-rs/clap/discussions/5332

Fixes: #4501

The value_name is not necessary for boolean flags.

This can be used in order to refer old working-copy commit, for example. If
we find it's useful, maybe we can add an infix syntax later.

Closes #1283

This isn't fancy, but I couldn't find a better abstraction. Note that
MutableRepo::base_repo() isn't removed as it has to return &Arc<_>, whereas
<ReadonlyRepo as Repo>::base_repo() can't return &Arc<_>.

This patch replaces all call sites with present(trunk()), and adds an explicit
check for unresolvable trunk(). If we add coalesce() expression, maybe it can
be rewritten to coalesce(present(trunk()), builtin_trunk()).

Fixes #4616

Signed-off-by: Austin Seipp <aseipp@pobox.com>

Bumps the github-dependencies group with 1 update: [actions/upload-artifact](https://github.com/actions/upload-artifact).


Updates `actions/upload-artifact` from 4.4.2 to 4.4.3
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](https://github.com/actions/upload-artifact/compare/84480863f228bb9747b473957fcc9e309aa96097...b4b15b8c7c6ac21ea08fcf65892d2ee8f75cf882)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: github-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

Bumps the github-dependencies group with 1 update: [actions/upload-artifact](https://github.com/actions/upload-artifact).


Updates `actions/upload-artifact` from 4.4.1 to 4.4.2
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](https://github.com/actions/upload-artifact/compare/604373da6381bf24206979c74d06a550515601b9...84480863f228bb9747b473957fcc9e309aa96097)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: github-dependencies
...

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This allows 'squash' to be executed more easily from a programmatic context

The id.shortest() template prints a warning and falls back to repo-global
resolution. This seems better than erroring out. There are a few edge cases
in which the short-prefixes resolution can fail unexpectedly. For example, the
trunk() revision might not exist in operations before "jj git clone".

The idea is that the disambiguation index can be loaded from a repo which is
different from the symbol resolution context.

Suppose we add at_operation(op, expr) revset, a symbol inside at_operation()
expression will have to be resolved within that operation, whereas the
disambiguation index is cached globally by WorkspaceCommandHelper. We could
build temporary disambiguation index for each at-op repo, but that would be
complicated implementation-wise, and wouldn't be useful. For example, a query
"x | at_operation(@-, x)" might be resolved to "xy | at_operation(@-, xz)"
if disambiguation index were reloaded for the @- operation. Instead, the
short change ID "x" can be disambiguated to "xy", then resolved to the
corresponding commit IDs at each operation.

Callers might want to fall back to an empty index if context.populate() failed.

This unblocks reuse of a symbol resolver instance for a different repo view
specified by at_operation() revset. See later commits for details. It's also
easier to handle error if there is a single function that can fail.

Bumps the github-dependencies group with 2 updates: [actions/checkout](https://github.com/actions/checkout) and [github/codeql-action](https://github.com/github/codeql-action).


Updates `actions/checkout` from 4.2.0 to 4.2.1
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/d632683dd7b4114ad314bca15554477dd762a938...eef61447b9ff4aafe5dcd4e0bbf5d482be7e7871)

Updates `github/codeql-action` from 3.26.11 to 3.26.12
- [Release notes](https://github.com/github/codeql-action/releases)
- [Changelog](https://github.com/github/codeql-action/blob/main/CHANGELOG.md)
- [Commits](https://github.com/github/codeql-action/compare/6db8d6351fd0be61f9ed8ebd12ccd35dcec51fea...c36620d31ac7c881962c3d9dd939c40ec9434f2b)

---
updated-dependencies:
- dependency-name: actions/checkout
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: github-dependencies
- dependency-name: github/codeql-action
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: github-dependencies
...

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Bumps the cargo-dependencies group with 3 updates: [clap](https://github.com/clap-rs/clap), [clap_complete](https://github.com/clap-rs/clap) and [clap_complete_nushell](https://github.com/clap-rs/clap).


Updates `clap` from 4.5.19 to 4.5.20
- [Release notes](https://github.com/clap-rs/clap/releases)
- [Changelog](https://github.com/clap-rs/clap/blob/master/CHANGELOG.md)
- [Commits](https://github.com/clap-rs/clap/compare/clap_complete-v4.5.19...clap_complete-v4.5.20)

Updates `clap_complete` from 4.5.32 to 4.5.33
- [Release notes](https://github.com/clap-rs/clap/releases)
- [Changelog](https://github.com/clap-rs/clap/blob/master/CHANGELOG.md)
- [Commits](https://github.com/clap-rs/clap/compare/clap_complete-v4.5.32...clap_complete-v4.5.33)

Updates `clap_complete_nushell` from 4.5.3 to 4.5.4
- [Release notes](https://github.com/clap-rs/clap/releases)
- [Changelog](https://github.com/clap-rs/clap/blob/master/CHANGELOG.md)
- [Commits](https://github.com/clap-rs/clap/compare/clap_complete_nushell-v4.5.3...clap_complete_nushell-v4.5.4)

---
updated-dependencies:
- dependency-name: clap
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: cargo-dependencies
- dependency-name: clap_complete
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: cargo-dependencies
- dependency-name: clap_complete_nushell
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: cargo-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

It no longer makes sense to handle missing root commit by the revset frontend,
but panicking wouldn't be good either. Let's make it error out.

This removes an invalid View state from the root operation.

Note that the root index will have to be reindexed in order to resolve "root()"
in the root operation. I don't think this would practically matter, so this
patch doesn't bump the index version to invalidate the existing indexes.

See also 48a9f9ef56c1 "repo: use Transaction for creating repo-init operation."

See the next patch for why. It might look odd that OpStore depends on the root
CommitId, but that seems okay because OpStore manages Views, and a View is
basically a set of CommitIds.

It's hosted by RepoLoader for now. I'm not sure if we'll need a higher-level
abstraction like Store.

I'll add a few helper methods to RepoLoader. It seems also nicer that
repo.loader() doesn't allocate new RepoLoader.

We didn't have any guidelines about what to include in a commit
message. Others have already written good guides for that. This commit
adds a link to one. I also added a sentence about explaining the
reason for a change, since I think that's particularly often missed
(I'm sure I also miss it sometimes - don't hesitate to point out when
that happens).

It's generally more useful to say something like "revset: use Self to
refer to expressions of the same type" than "lib: use Self to refer to
revset expressions of the same type ", so let's try to clarify that.

Bumps the cargo-dependencies group with 3 updates: [futures](https://github.com/rust-lang/futures-rs), [once_cell](https://github.com/matklad/once_cell) and [proc-macro2](https://github.com/dtolnay/proc-macro2).


Updates `futures` from 0.3.30 to 0.3.31
- [Release notes](https://github.com/rust-lang/futures-rs/releases)
- [Changelog](https://github.com/rust-lang/futures-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/futures-rs/compare/0.3.30...0.3.31)

Updates `once_cell` from 1.20.1 to 1.20.2
- [Changelog](https://github.com/matklad/once_cell/blob/master/CHANGELOG.md)
- [Commits](https://github.com/matklad/once_cell/compare/v1.20.1...v1.20.2)

Updates `proc-macro2` from 1.0.86 to 1.0.87
- [Release notes](https://github.com/dtolnay/proc-macro2/releases)
- [Commits](https://github.com/dtolnay/proc-macro2/compare/1.0.86...1.0.87)

---
updated-dependencies:
- dependency-name: futures
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: cargo-dependencies
- dependency-name: once_cell
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: cargo-dependencies
- dependency-name: proc-macro2
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: cargo-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

This enables more scripting use cases where the caller may wish to parse stdout for programmatic purposes.

For #3673, we will have aliases such as:
```toml
'upload(revision)' = [
["fix", "-r", "$revision"],
["lint", "-r", "$revision"],
["git", "push", "-r", "$revision"],
]
```

Template aliases:
1) Start as Config::Value
2) Are converted to String
3) Are placed in the alias map
4) Expand to a TemplateExpression type via expand_defn.

However, command aliases:
1) Start as Config::Value
2) Are converted to Vec<Vec<String>>
3) Are placed in an alias map
4) Do not expand

Thus, AliasesMap will need to support non-string values.

`jj git push` has a `--bookmark` argument, which takes a list of
bookmarks to push to the Git remote. They'll become branches on the
Git remote. `jj git fetch` has a `--branch` argument, which takes a
list of Git branches to fetch. They'll become bookmarks once
fetched. So the naming is consistent, but the reasoning is quite
subtle. Let's provide the other name as a hidden alias to help users
who get it wrong.

Bumps the github-dependencies group with 1 update: [actions/upload-artifact](https://github.com/actions/upload-artifact).


Updates `actions/upload-artifact` from 4.4.0 to 4.4.1
- [Release notes](https://github.com/actions/upload-artifact/releases)
- [Commits](https://github.com/actions/upload-artifact/compare/50769540e7f4bd5e21e526ee35c689e35e0d6874...604373da6381bf24206979c74d06a550515601b9)

---
updated-dependencies:
- dependency-name: actions/upload-artifact
dependency-type: direct:production
update-type: version-update:semver-patch
dependency-group: github-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

Just because it's shorter.

Since context lines are styled in the same way as diff lines, it makes sense
to highlight words within context lines.

This should make the next patch a bit easier to read.

These flags only apply to line-based diffs. This is easy, and seems still useful
to highlight whitespace changes (that could be ignored by line diffing.)

I've added short options only to "diff"-like commands. It seemed unclear if
they were added to deeply-nested commands such as "op log".

Closes #3781

UnifiedDiffOptions could be wrapped by GitDiffOptions, but there are no Git-diff
specific options right now.

I'm going to add an options struct for git diff, but GitOptions, UnifiedOptions,
StatOptions, etc. sound odd.

We're likely to use the right (or new) context lines in rendered diffs, but
it's odd that the hunks iterator choose which context hunk to return. We'll
also need both contents to calculate left/right line numbers.

Since the hunk content types are the same, I also split enum DiffHunk into
{ kind, contents } pair.

This change made some diff benches slow, maybe because the generated code
becomes slightly worse due to the added abstraction? I'll revisit the
performance problem later. There are a couple of ways to mitigate it.

```
group new old
----- --- ---
bench_diff_git_git_read_tree_c 1.02 61.0±0.23µs 1.00 59.7±0.38µs
bench_diff_lines/modified/10k 1.00 41.6±0.24ms 1.02 42.3±0.22ms
bench_diff_lines/modified/1k 1.00 3.8±0.07ms 1.00 3.8±0.03ms
bench_diff_lines/reversed/10k 1.29 23.4±0.20ms 1.00 18.2±0.26ms
bench_diff_lines/reversed/1k 1.05 517.2±5.55µs 1.00 493.7±59.72µs
bench_diff_lines/unchanged/10k 1.00 3.9±0.10ms 1.08 4.2±0.10ms
bench_diff_lines/unchanged/1k 1.01 356.8±2.33µs 1.00 353.7±1.99µs
```
(I don't get stable results on my noisy machine, so the results would vary.)

The added comparison functions correspond to --ignore-all-space and
--ignore-space-change. --ignore-space-at-eol can be combined with the other
flags, so it will have to be implemented as a preprocessing function.
--ignore-blank-lines will also require some change in the tokenizer function.

This could be implemented as a newtype `Wrapper<'a>(&'a [u8])`, but a lifetime
of the wrap function couldn't be specified correctly:

fn diff(left: &[u8], right: &[u8], wrap_fn: F, ..)
where
F: for<'a> Fn(&'a [u8]) -> W<'a>, // F::Output<'a> can't be specified
W: Copy + Eq + Hash

If the wrapper were of `&Wrapper([u8])` type, `Fn(&[u8]) -> &W` works. However,
it means we can no longer set comparison parameter (such as Regex) dynamically.

Another idea is to add some filter function of `Fn(&[u8]) -> Cow<'_, [u8]>`
type, but I don't think we would want to pay the allocation cost in
hashing/comparison code. `Fn(&[u8]) -> impl Iterator<Item = &[u8]>` might work,
but it would be equally complex.

We'll use low-level HashTable to customize Eq/Hash without implementing newtype
wrappers.

Unneeded default features are disabled for now. Note that the new default
hasher, foldhash, is released under the Zlib license, which isn't currently
included in the allow list.

`.clone()` is more explicit when we already have an object
of the right type.