The `heads()` revset function with one argument is the counterpart to
`roots()`. Without arguments, it returns the visible heads in the
repo, i.e. `heads(all())`. The two use cases are quite different, and
I think it would be good to clarify that the no-arg form returns the
visible heads, so let's split that out to a new `visible_heads()`
function.
This serves the role of limit() in Mercurial. Since revsets in JJ is
(conceptually) an unordered set, a "limit" predicate should define its
ordering criteria. That's why the added predicate is named as "latest".
Closes#1110
@joyously found `o` confusing because it's a valid change id prefix. I
don't have much preference, but `●` seems fine. The "ascii",
"ascii-large", and "legacy" graph styles still use "o".
I didn't change `@` since it seems useful to have that match the
symbol used on the CLI. I don't think we want to have users do
something like `jj co ◎-`.
The added expect_arguments() is basically a copy from the template_parser.
I'll reimplement it to support keyword arguments, so I don't care much about
the current implementation.
I leave expect_no/one_argument() as wrappers because parsing 0/1 arguments
is pretty common.
Error messages are slightly changed. I personally prefer not to add extra
code for singular/plural handling, but if we do, I'll add 'if N == 1' case.
I don't think need to write non-UTF8 bytes to our config files. If we
ever do (maybe to test that we give the user a reasonable error
message), we add a custom function for that.
This is ugly, but we need a special case because root_change_id and
root_commit_id aren't equal but share the same prefix bytes. In practice,
no one would care for the shortest root id prefix, but we'll need to deal
with a similar problem when migrating prefix id resolution to repo layer.
Suggested by @arxanas.
Actually, it's easier to support these infix ops than erroring out, but I
don't want to make revset syntax more cryptic. "x- y" can't be handled by
this rule because "x-" is parsed as a parents expression.
Because a unary negation node '~y' is more primitive than the corresponding
difference node 'x~y', '~y' is easier to deal with while rewriting the tree.
That's the main reason to add RevsetExpression::NotIn node.
As we have a NotIn node, it makes sense to add an operator for that. This
patch reuses '~' token, which I feel intuitive since the other set operators
looks like bitwise ops. Another option is '!'.
The unary '~' operator has the highest precedence among the set operators,
but they are lower than the ranges. This might be counter intuitive, but
useful because a prefix range ':x' can be negated without parens.
Maybe we can remove the redundant infix operator 'x ~ y', but it isn't
decided yet.
Function parameters are processed as local symbols while substituting
alias expression. This isn't as efficient as Mercurial which caches
a tree of fully-expanded function template, but that wouldn't matter in
practice.
Let's acknowledge everyone's contributions by replacing "Google LLC"
in the copyright header by "The Jujutsu Authors". If I understand
correctly, it won't have any legal effect, but maybe it still helps
reduce concerns from contributors (though I haven't heard any
concerns).
Google employees can read about Google's policy at
go/releasing/contributions#copyright.
Aliases are loaded at WorkspaceCommandHelper::new() as it's easier to warn
invalid declarations there. Not all commands use revsets, but many do, so
I think it's okay to always pay the loading cost. Parsing the declaration
part (i.e. a symbol) should be fast anyway.
The nested error message isn't super readable, but seems good enough.
Config syntax to bikeshed:
- naming: [revset-alias] vs [revset-aliases] ?
- function alias will need quotes: 'f(x)' = 'x'
I'm thinking of adding alias expansion at this stage, and it would be a bit
tedious to pass around mutable context by function parameter. So let's reduce
the number of the intermediate functions.
This also produces a better error message.
