cli: make pager configurable per command

[bryceberger]

Closes #5217

Allow ui.pager to be set as a table like so:

[ui]
pager.status = ":none"
pager.log = { command = ["less", "-FRX"], env = { LESSCHARSET = "utf-8" } }
pager.diff = ["delta", "..."]
pager.default = "..."

ui.pager.log is used for jj log, ui.pager.diff for jj diff, etc. The full name of the highest level subcommand is used, i.e. jj operation diff uses ui.pager.operation. The value ":none" disables paging for the selected command. If a command is not specifically mentioned, the value of ui.pager.default is used.

The old behaviour is unchanged, i.e. ui.pager = ["less", "-FRX"] will set the pager for all subcommands.

Checklist

If applicable:

• I have updated CHANGELOG.md
• I have updated the documentation (README.md, docs/, demos/)
• I have updated the config schema (cli/src/config-schema.json)
• I have added tests to cover my changes

[bryceberger]

Unsure how to update config-schema.json for this. The current entry for pager just says "type": "string", which isn't true.

Also unsure if / where there are tests for pagers. I was unable to find any on a cursory glance.

[yuja]

[ui]
pager.status = ":none"
pager.log = { command = ["less", "-FRX"], env = { LESSCHARSET = "utf-8" } }
pager.diff = ["delta", "..."]
pager.default = "..."

I think it's better to not overuse ":<type>" syntax. How about adding a separate table for per-table pager configuration?

[ui]
paginate = "auto"  # default
pager = "..."  # default

[<table-for-per-command-pager-options>]
status.paginate = "never"
diff.pager = ["delta", "..."]

# or generic per-command table like this?
[commands.status]
ui.paginate = "never"

# or extend the conditional table?
[[--scope]]
--when.commands = ["status"]
ui.paginate = "never"

The full name of the highest level subcommand is used, i.e. jj operation diff uses ui.pager.operation.

I think "file show" and "file list" are quite different, and the user might want to enable pager only for one of them.

[bryceberger]

I'm intrigued by extending the [[--scope]] rules.

The rule for --when.repositories = ["a", "b"] is to match "a" | "b" --- would have to put some thought into how to match operation, operation diff, and diff separately. Maybe "operation.diff"?

Currently, jj_lib::config_resolver::resolve() throws away the layer if its --when doesn't match. Thinking of changing ScopeCondition::matches() to return Option<bool>, with None meaning "not enough information to resolve", i.e. resolving --when.repository during cli_util::run_internal but waiting until commands::run_command to resolve --when.commands.

[yuja]

The rule for --when.repositories = ["a", "b"] is to match "a" | "b" --- would have to put some thought into how to match operation, operation diff, and diff separately. Maybe "operation.diff"?

or "operation diff"? The [colors] table uses space-separated string.

Currently, jj_lib::config_resolver::resolve() throws away the layer if its --when doesn't match. Thinking of changing ScopeCondition::matches() to return Option<bool>, with None meaning "not enough information to resolve", i.e. resolving --when.repository during cli_util::run_internal but waiting until commands::run_command to resolve --when.commands.

run_command() calls resolve() multiple times, so I think it's okay to omit --when.commands conditionals until the command name becomes available. That's how --repository path is resolved.