These are read-line-like bindings which we'd like to minimize in
insert mode in general.
In particular these two are troublesome if you have a low
`editor.idle-timeout` config and are using LSP completions: the
behavior of C-n/C-p switches from moving down/up lines to moving
down/up the completion menu, so if you hit C-n too quickly
expecting to be in the completion menu, you'll end up moving down
a line instead. Using C-p moves you back up the line but doesn't
re-trigger the completion menu. This kind of timing related change
to behavior isn't realistically that big of a deal but it can be
annoying.
* Fix tab highlight when tab is partially visible
* Make it style based, and not truncation based
Dealing with truncating is a mess, especially when it comes to wide
unicode graphemes. This way it should work no matter what.
* Inline style calculation into branches
* Fix incorrect indent guide styling
Before the indent guides on top of whitespace inherited the theme
from them. Now they do not.
* Fix dark_plus theme indent_guides
* Use whitespace style as fallback for indent-guide
* Fix dark_plus theme indent_guides
* Move indent_guide style patching out of loop
* Avoid setting stdin handle when not necessary
Avoid setting the stdin handle in `shell_impl` when the input argument
is None.
This permits to run commands with no stdin with :sh
* refactoring to avoid code duplication
* making clippy happy
* Process variable name fix
Indent style may change when choosing a language with `:set-language`.
Line-endings most likely will not change, but `:set-language` should
have a similar effect as reloading a file (`:reload`), plus the two
are currently grouped in the implementation and line-ending detection
is not particularly expensive.
* Change default formatter for any language
* Fix clippy error
* Close stdin for Stdio formatters
* Better indentation and pattern matching
* Return Result<Option<...>> for fn format instead of Option
* Remove unwrap for stdin
* Handle FormatterErrors instead of Result<Option<...>>
* Use Transaction instead of LspFormatting
* Use Transaction directly in Document::format
* Perform stdin type formatting asynchronously
* Rename formatter.type values to kebab-case
* Debug format for displaying io::ErrorKind (msrv fix)
* Solve conflict?
* Use only stdio type formatters
* Remove FormatterType enum
* Remove old comment
* Check if the formatter exited correctly
* Add formatter configuration to the book
* Avoid allocations when writing to stdin and formatting errors
* Remove unused import
Co-authored-by: Gokul Soumya <gokulps15@gmail.com>
The language server sends a char offset range within the
signature help label text to highlight as the current parameter,
but helix uses byte offset ranges for rendering highlights. This
was brought up in the [review of the original signature help PR][1],
but the ranges were being highlighted correctly, and there were no
out of bound or indexing panics. Turns out rust-analyzer was
[incorrectly sending byte offsets] instead of char offsets and this
made it seem like all was well and good with offsets in helix during
initial testing.
[1]: https://github.com/helix-editor/helix/pull/1755#discussion_r906715371
[2]: https://github.com/rust-lang/rust-analyzer/pull/12272
* auto pair-removal
Fixes https://github.com/helix-editor/helix/issues/1673
* autopairs removal: use doc autopairs
* autopairs-removal: limit to one-char selections
* use single_grapheme() to check if range is one char
* fix errouneous deletes of " and other symmetric autopairs when at buffer start
Co-authored-by: Houkime <>
* add statusline element to display file line endings
* run cargo fmt --all
* change the word *ending* from plural to singular
* support for the unicode-lines feature flag
* Add lsp signature help
* Do not move signature help popup on multiple triggers
* Highlight current parameter in signature help
* Auto close signature help
* Position signature help above to not block completion
* Update signature help on backspace/insert mode delete
* Add lsp.auto-signature-help config option
* Add serde default annotation for LspConfig
* Show LSP inactive message only if signature help is invoked manually
* Do not assume valid signature help response from LSP
Malformed LSP responses are common, and these should not crash the
editor.
* Check signature help capability before sending request
* Reuse Open enum for PositionBias in popup
* Close signature popup and exit insert mode on escape
* Add config to control signature help docs display
* Use new Margin api in signature help
* Invoke signature help on changing to insert mode
* feat(statusline): add the file type (language id) to the status line
* refactor(statusline): move the statusline implementation into an own struct
* refactor(statusline): split the statusline implementation into different functions
* refactor(statusline): Append elements using a consistent API
This is a preparation for the configurability which is about to be
implemented.
* refactor(statusline): implement render_diagnostics()
This avoid cluttering the render() function and will simplify
configurability.
* feat(statusline): make the status line configurable
* refactor(statusline): make clippy happy
* refactor(statusline): avoid intermediate StatusLineObject
Use a more functional approach to obtain render functions and write to
the buffers, and avoid an intermediate StatusLineElement object.
* fix(statusline): avoid rendering the left elements twice
* refactor(statusline): make clippy happy again
* refactor(statusline): rename `buffer` into `parts`
* refactor(statusline): ensure the match is exhaustive
* fix(statusline): avoid an overflow when calculating the maximal center width
* chore(statusline): Describe the statusline configurability in the book
* chore(statusline): Correct and add documentation
* refactor(statusline): refactor some code following the code review
Avoid very small helper functions for the diagnositcs and inline them
instead.
Rename the config field `status_line` to `statusline` to remain
consistent with `bufferline`.
* chore(statusline): adjust documentation following the config field refactoring
* revert(statusline): revert regression introduced by c0a1870
* chore(statusline): slight adjustment in the configuration documentation
* feat(statusline): integrate changes from #2676 after rebasing
* refactor(statusline): remove the StatusLine struct
Because none of the functions need `Self` and all of them are in an own
file, there is no explicit need for the struct.
* fix(statusline): restore the configurability of color modes
The configuration was ignored after reintegrating the changes of #2676
in 8d28f95.
* fix(statusline): remove the spinner padding
* refactor(statusline): remove unnecessary format!()
Ctrl-based shortcuts are common in numerous applications.
This change:
- Adds Ctrl+{Left/Right/Backspace/Delete} for word-wise movement/deletion in prompt, picker, …
- Removes Alt-Left and Alt-Right in prompt, picker, …
- Adds Alt-Delete in insert mode for forward word deletion
In some terminals, Alt-Backspace might not work because it is ambigous.
See: https://github.com/helix-editor/helix/pull/2193#issuecomment-1105042501
Hence, Alt alternative is not removed.
* Fix backwards selection duplication widening bug
* Add integration tests
* Make tests line-ending agnostic
Make tests line-ending agnostic
Use indoc to fix tests
Fix line-ending on test input
* Refactor menu::Item to accomodate external state
Will be useful for storing editor state when reused by pickers.
* Add some type aliases for readability
* Reuse menu::Item trait in picker
This opens the way for merging the menu and picker code in the
future, since a picker is essentially a menu + prompt. More
excitingly, this change will also allow aligning items in the
picker, which would be useful (for example) in the command palette
for aligning the descriptions to the left and the keybinds to
the right in two separate columns.
The item formatting of each picker has been kept as is, even though
there is room for improvement now that we can format the data into
columns, since that is better tackled in a separate PR.
* Rename menu::Item::EditorData to Data
* Call and inline filter_text() in sort_text() completion
* Rename diagnostic picker's Item::Data
* Sort themes by score & then name
Previously the themes were appearing unordered after typing ':theme '.
This sorts them first by fuzzy score and then by name so that they
generally appear in a more ordered fashion in the initial list.
The sort by name does not really pay off when there is a score so an
alternative approach would be to sort by name if there is string to
fuzzy match against and otherwise sort by score.
I've lowercased the names as that avoids lower case & upper case letters
being sorted into separate groups. There might be a preferable approach
to that though.
* Sort language & files by score then name
And change to use sort_unstable_by instead of sort_unstable_by_key as it
allows us to avoid some allocations.
I don't fully understand the flow of the 'filename_impl' function but
this seems to deliver the desired results.
* Remove unnecessary reference
Co-authored-by: Michael Davis <mcarsondavis@gmail.com>
Co-authored-by: Michael Davis <mcarsondavis@gmail.com>
* adds --vsplit and --hsplit arguments
* moved comment
* fixed lint (third time's a charm)
* changed vsplit and hsplit from two separate bools to type Option<Layout>, and some cleanup
* delete_backwards_char accepts any type of whitespace
* Fix inconsistency, where unicode whitespaces are treated as normal whitespaces
* Changed back to direct whitespace match
* Only accept explicit whitespace / tabs
Co-authored-by: s0LA1337 <dreamer@neoncity.dev>
* Add mode specific styles
In similar vein to neovim's lualine and similar statusline packages this
allows helix users to style their mode based on which mode it is thus
making each mode more visually distinct at a glance
* Add an example based on rosepine
* Add editor.colors-mode config
* Document statusline mode styles
* Add workspace and document diagnostics picker
fixes#1891
* Fix some of @archseer's annotations
* Add From<&Spans> impl for String
* More descriptive parameter names.
* Adding From<Cow<str>> impls for Span and Spans
* Add new keymap entries to docs
* Avoid some clones
* Fix api change
* Update helix-term/src/application.rs
Co-authored-by: Bjorn Ove Hay Andersen <bjrnove@gmail.com>
* Fix a clippy hint
* Sort diagnostics first by URL and then by severity.
* Sort diagnostics first by URL and then by severity.
* Ignore missing lsp severity entries
* Add truncated filepath
* Typo
* Strip cwd from paths and use url-path without schema
* Make tests a doctest
* Better variable names
Co-authored-by: Falco Hirschenberger <falco.hirschenberger@itwm.fraunhofer.de>
Co-authored-by: Bjorn Ove Hay Andersen <bjrnove@gmail.com>
- Simplified match statements by destructuring MouseEvent struct
at the top and then matching on event.kind.
- Extracted out closures for calculating (1) position and view
of mouse click and (2) gutter coordinates and view of mouse click.
* Add single width left margin for completion popup
* Clear with ui.menu style before rendering menu
When rendering a completion popup, the popup component will clear
the area with ui.popup and then the menu component would draw over
it using a table component. We remove the left edge of the area
before passing it to the table component (so that it will be left
as padding), and the table component uses ui.menu as the style.
If ui.menu and ui.popup are different the left edge of the popup
will look different from the rest of the popup. We avoid this by
clearing the whole area with ui.menu in Menu::render
* check selection's visible width when copying on mouse click
Mouse-click-up copies the selection produced by dragging. The event
is ignored if the selection has a width of 1 though so you don't
copy when clicking rather than dragging. The current check copies
text when it has a visible width of 1 but is actually multiple
characters in the rope like a CRLF line-ending. With this change
we check the unicode width of the character(s) in the selection
rather than the range length, so clicking on a CRLF line-ending
does not copy.
* use range.fragment to simplify getting the primary selection width
* redetect indent and line endings after language server replaces document
* removes nested if
* always redetect indent and line endings after format
This reverts commit 764d14f55894dc7213e48022dfa0f91829b8ef59.
The scrollbar length used to increase with more entries in the menu,
which was counter-intuitive to how scrollbars worked in most
applications. Turns out there was a typo in the floor division
implementation :)
The command palette previously used + as a delimiter for denoting
a single key in a key sequence, (like C+w). This was at odds with
how the statusline displayed them with pending keys (like <C-w>).
This patch changes the palette formatting to the statusline formatting
* feat: make `move_vertically` aware of tabs and wide characters
* refactor: replace unnecessary checked_sub with comparison
* refactor: leave pos_at_coords unchanged and introduce separate pos_at_visual_coords
* style: include comment to explain `pos_at_visual_coords` breaking condition
* refactor: use `pos_at_visual_coords` in `text_pos_at_screen_coords`
* feat: make `copy_selection_on_line` aware of wide characters
* Default rulers color to red
Currently if the theme a user is using doesn't have `ui.virtual.rulers`
set and they set up a ruler it just fails silently making it really hard
to figure out what went wrong. Did they set incorrectly set the ruler?
Are they using an outdated version of Helix that doesn't support rulers?
This happened to me today, I even switched to the default theme with
the assumption that maybe my theme just doesn't have the rulers setup
properly and it still didn't work.
Not sure if this is a good idea or not, feel free to suggest better
alternatives!
* Use builtin Style methods instead of Bevy style defaults
Co-authored-by: Michael Davis <mcarsondavis@gmail.com>
* Only default the style if there's no ui or ui.virtual
* Update themes style from ui.virtual to ui.virtual.whitespace
* Revert ui.virtual change in onelight theme
* Prefer unwrap_or_else
Co-authored-by: Michael Davis <mcarsondavis@gmail.com>
During write-quit, if the file fails to be written for any reason, helix
will still quit without saving the changes. This fixes this behavior by
introducing fallibility to the asynchronous job queues. This will also
benefit all contexts which may depend on these job queues.
Fixes#1575
When a new View of a Document is created, a default cursor of 0, 0 is
created, and it does not get normalized to a single width cursor until
at least one movement of the cursor happens. This appears to have no
practical negative effect that I could find, but it makes tests difficult
to work with, since the initial selection is not what you expect it to be.
This changes the initial selection of a new View to be the width of the
first grapheme in the text.
* Use new macro syntax for encoding sequences of keys
* Make convenience helpers for common test pattern
* Use indoc for inline indented raw strings
* Add feature flag for integration testing to disable rendering
- Add file-picker.follow-symlinks configuration option (default is true), this
also controls if filename and directory completers follow symlinks.
- Update FilePicker to set editor error if opening a file fails, instead of
panicing.
Fix#1548Fix#2246
In certain circumstances it was possible to get into an infinite loop
when replaying macros such as when different macros attempt to replay
each other.
This commit adds changes to track which macros are currently being
replayed and prevent getting into infinite loops.
When a goto command is cancelled, the jumplist should remain unchanged.
This commit delays saving the current selection to the jumplist until
jumping to a reference.
* Add shrink equivalent of extend_to_line_bounds
* Add a check for being past rope end in end position calc
* Include the EOL character in calculations
* Bind to `A-x` for now
* Document new keybind
* add Tree::swap_split_in_direction()
* add swap_view_{left,down,up,right} commands, bound to H,J,K,L
respectively in the Window menu(s)
* add test for view swapping
* feat(theme): add separate diagnostic colors
This commit adds separate diagnostic highlight colors for the different
types of LSP severities. If the severity type doesn't exist or is
unknown, we use some fallback coloring which was in use before this
commit.
Some initial color options were also added in the theme.toml
Resolves issue #2157
* feat(theme): add docs for new diagnostic options
* feat(theme): adjust defaults & reduce redundancy
- the different colors for different diagnostic severities are now
disabled in the default theme, instead diagnostics are just generally
underlined (as prior to the changes of this feature)
- the theme querying is now done once instead of every iteration in the
loop of processing every diagnostic message
* support insert register in prompt
* use next_char_handler instead of a flag
* Fix clippy issue
* show autoinfo when inserting register
* Revert "show autoinfo when inserting register"
This reverts commit 5488344de1.
* use completion instead of autoinfo
autoinfo is overlapped when using prompt
* recalculate_completion after inserting register
* Update helix-term/src/ui/prompt.rs
Co-authored-by: Ivan Tham <pickfire@riseup.net>
Co-authored-by: Ivan Tham <pickfire@riseup.net>
Change the layout of existing split view from horizontal to vertical and
vica-versa. It only effects the focused view and its siblings, i.e. not
recursive.
Command is mapped to 't' or 'C-t' under the Window menus.
This made sense initially when the implementation was still new (so we
got user reports more frequently), but a parsing error now generally
signifies a language server isn't properly implementing the spec.
Currently ctrl-w in insert mode deletes the cursor which results in
unexpected behavior. The patch also reduces the selection to cursor before
performing prev word to remove the behavior of removing unnecessary text
when nothing should be removed.
1. `::#(|)#::` after `ctrl-w` should be `#(|)#::`, previously `#(|)#:`
2. `#(|::)#` after `ctrl-w` should be `#(|::)#`, previously `#(|)#`
Fix#2390
Inserting a newline currently collapses any connected selections when inserting
or appending. It's happening because we're reducing the selections down to
their cursors (`let selection = ..` line) and then computing the new selection
based on the cursor. We're discarding the original head and anchor information
which are necessary to emulate Kakoune's behavior.
In Kakoune, inserting a newline retains the existing selection and _slides_
it (moves head and anchor by the same amount) forward by the newline and
indentation amount. Appending a newline extends the selection to include the
newline and any new indentation.
With the implementation of insert_newline here, we slide by adding the global
and local offsets to both head and anchor. We extend by adding the global
offset to both head and anchor but the local offset only to the head.
* Making the 'set-option' command help more descriptive.
* Adding the generated docs
* Making the message multi-line
* Replace newline with break in generated docs
* add reflow command
Users need to be able to hard-wrap text for many applications, including
comments in code, git commit messages, plaintext documentation, etc. It
often falls to the user to manually insert line breaks where appropriate
in order to hard-wrap text.
This commit introduces the "reflow" command (both in the TUI and core
library) to automatically hard-wrap selected text to a given number of
characters (defined by Unicode "extended grapheme clusters"). It handles
lines with a repeated prefix, such as comments ("//") and indentation.
* reflow: consider newlines to be word separators
* replace custom reflow impl with textwrap crate
* Sync reflow command docs with book
* reflow: add default max_line_len language setting
Co-authored-by: Vince Mutolo <vince@mutolo.org>
Allow tab-completion to continue when there is only a single, unambigous
completion target which is a directory. This allows e.g. nested directories
to be quickly drilled down just by hitting <tab> instead of first selecting
the completion then hitting <enter>.
* add run_shell_command
* docgen
* fix command name
Co-authored-by: Blaž Hrastnik <blaz@mxxn.io>
* refactored Info::new
* show 'Command failed' if execution fails
* TypedCommand takes care of error handling and printing the error to the statusline.
* docgen
* use Popup instead of autoinfo
* remove to_string in format!
* Revert chage in info.rs
* Show "Command succeed" when success
* Fix info.rs
Co-authored-by: Blaž Hrastnik <blaz@mxxn.io>
When fiddling with paths in a :o prompt, one usually would want Ctrl-W to erase a path segment
rather than the whole path. This is how Ctrl-W works in e.g. (neo)vim out of the box.
Currently A-left move one word left and the behavior will be more
consistent for people coming GUI world if the key was changed to control
given that both browsers and editors like vscode uses C-left right by
default to move word rather than alt.
A-hl currently is not very consistent with hl when next object is
selected, since it may go up/down or left/right and this behavior is
confusing such that some people think it should swap the keys with A-jk,
so it is better to use A-pn since that only specifies two direction.
A-jk have the same issue as in it usually moves right and is not
consistent with the behavior of jk so people may think A-hl is better,
maybe A-oi is better here since A-hl will be swapped to A-pn, A-oi can
convey the meaning of in and out, similar to some window manager keys?
* feat(commands): better handling of buffer-close
Previously, when closing buffer, you would loose cursor position in other docs.
Also, all splits where the buffer was open would be closed.
This PR changes the behavior, if the view has also other buffer
previously viewed it switches back to the last one instead of the view
being closed. As a side effect, since the views are persisted,
the cursor history is persisted as well.
Fixes: https://github.com/helix-editor/helix/issues/1186
* Adjust buffer close behavior
* Remove closed documents from jump history
* Fix after rebase
* Fix ctrl-u on insert behavior
Now should follow vim behavior more
- no longer remove text on cursor
- no longer remove selected text while inserting
- first kill to start non-whitespace, start, previous new line
* Add comment for c-u parts
Select multiple line and open should be based on the whole selection
and not just the line of the cursor, which causes weird behavior like
opening in the middle of the selection which user might not expect.
* added command to extend selection to line above
* fixed view not scrolling up when reaching top of the screen
* refactored shared code into separate impl
* Send active diagnostics to LSP when requesting code actions.
This allows for e.g. clangd to properly send the quickfix code actions
corresponding to those diagnostics as options.
The LSP spec v3.16.0 introduced an opaque `data` member that would allow
the server to persist arbitrary data between the diagnostic and the code
actions request, but this is not supported yet by this commit.
* Reuse existing range_to_lsp_range functionality
hx --health output table's second and third columns were not showing
symbols like ✔ or ✘ to indicate whether LSP or DAP binaries were found.
This change adds these symbols to improve accessibility.
Fixes#1894
Signed-off-by: Nirmal Patel <npate012@gmail.com>
* Make `:write` create nonexistent subdirectories
Prompting as to whether this should take place remains a TODO.
* Move subdirectory creation to new `w!` command
The `file_picker_at_current_directory` command opens the file picker at
the current working directory (CWD). This can be useful when paired with
the built-in `:cd` command which changes the CWD.
It has been mapped to `space F` by default.
During a single HighlightEvent::Source, the highlight spans do not
change and we can merge them into a single style at the beginning
of the event and use it instead of re-computing it for every grapheme
* Add runtime language configuration (#1794)
* Add set-language typable command to change the language of current buffer.
* Add completer for available language options.
* Update set-language to refresh language server as well
* Add language id based config lookup on `syntax::Loader`.
* Add `Document::set_language3` to set programming language based on language
id.
* Update `Editor::refresh_language_server` to try language detection only if
language is not already set.
* Remove language detection from Editor::refresh_language_server
* Move document language detection to where the scratch buffer is saved.
* Rename Document::set_language3 to Document::set_language_by_language_id.
* Remove unnecessary clone in completers::language
when using helix over mosh, the screen doesn't get cleared and
characters get left all over the place until they are overwritten. with
this change, the screen gets properly cleared as soon as helix starts
The search implementation would start searching at the next grapheme
boundary after the previous selection. In case the next occurence of the
needle is immediately after the current selection, this occurence would
not be found (without wraparound) because the first grapheme is skipped.
The correct approach is to use the ensure_grapheme_boundary functions instead
of using the functions that skip unconditionally to the next grapheme.
Currently, the picker's re-using a few bindings which are also present
in the prompt. This causes some editing behaviours to not function on
the picker.
**Ctrl + k** and **Ctrl + j**
This should kill till the end of the line on prompt, but is overridden
by the picker for scrolling. Since there are redundancies (`Ctrl + p`,
`Ctrl + n`), we can remove it from picker.
**Ctrl + f** and **Ctrl + b**
This are used by the prompt for back/forward movement. We could modify
it to be Ctrl + d and Ctrl + u, to match the `vim` behaviour.
* WIP: Rework indentation system
* Add ComplexNode for context-aware indentation (including a proof of concept for assignment statements in rust)
* Add switch statements to Go indents.toml (fixes the second half of issue #1523)
Remove commented-out code
* Migrate all existing indentation queries.
Add more options to ComplexNode and use them to improve C/C++ indentation.
* Add comments & replace Option<Vec<_>> with Vec<_>
* Add more detailed documentation for tree-sitter indentation
* Improve code style in indent.rs
* Use tree-sitter queries for indentation instead of TOML config.
Migrate existing indent queries.
* Add documentation for the new indent queries.
Change xtask docgen to look for indents.scm instead of indents.toml
* Improve code style in indent.rs.
Fix an issue with the rust indent query.
* Move indentation test sources to separate files.
Add `#not-kind-eq?`, `#same-line?` and `#not-same-line` custom predicates.
Improve the rust and c indent queries.
* Fix indent test.
Improve rust indent queries.
* Move indentation tests to integration test folder.
* Improve code style in indent.rs.
Reuse tree-sitter cursors for indentation queries.
* Migrate HCL indent query
* Replace custom loading in indent tests with a designated languages.toml
* Update indent query file name for --health command.
* Fix single-space formatting in indent queries.
* Add explanation for unwrapping.
Co-authored-by: Triton171 <triton0171@gmail.com>
* publish a source tarball with version and grammars
* include_str! the release version from a VERSION file
* remove setting of .version file from tag
don't need this anymore since the file is checked into source
* Move top level lsp config to editor.lsp
This is mainly done to accomodate the new lsp.signature-help config
option that will be introduced in https://github.com/helix-editor/helix/pull/1755
which will have to be accessed by commands. The top level config
struct is split and moved to different places, making the relocation
necessary
* Revert rebase slipup
This avoids costly conversions via byte_to_char (which are then
reversed back into bytes internally in Ropey).
Reduces time spent in slice/byte_to_char from ~24% to ~5%.
When the picker results output is empty, movement actions result in a panic:
```
thread 'main' panicked at 'attempt to calculate the remainder with a divisor of zero', helix-term/src/ui/picker.rs:420:31
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```
This could be a no-op instead when the matches length is zero.
Currently match is finding the match based on the anchor rather than the
head (cursor) so this behavior is rather unexpected when user is doing
a match but a different item was matched instead when the selection is
more than one character.
This restores much of the behavior that existed before this PR:
helix will build the grammars when compiling. The difference is that
now fetching is also done during the build phase and is done much
more quickly - both shallow and in parallel.
This is a rather large refactor that moves most of the code for
loading, fetching, and building grammars into a new helix-loader
module. This works well with the [[grammars]] syntax for
languages.toml defined earlier: we only have to depend on the types
for GrammarConfiguration in helix-loader and can leave all the
[[language]] entries for helix-core.
The vision with 'use-grammars' is to allow the long-requested feature
of being able to declare your own set of grammars that you would like.
A simple schema with only/except grammar names controls the list
of grammars that is fetched and built. It does not (yet) control which
grammars may be loaded at runtime if they already exist.
build_grammars adapts the functionality that previously came from
helix-syntax to be used at runtime from the command line flags.
fetch_grammars wraps command-line git to perform the same actions
previously done in the scripts in #1560.
helix-syntax mostly existed for the sake of the build task which
checks and compiles the submodules. Since we won't be relying on
that process anymore, it doesn't end up making much sense to have
a very thin crate just for some functions that we could port to
helix-core.
The remaining build-related code is moved to helix-term which will
be able to provide grammar builds through the --build-grammars CLI
flag.