nes: make tryRebase conflict limit exp-configurable

[ulugbekna]

Summary

The tryRebase logic uses a hard-coded limit of 5 characters (maxImperfectAgreementLength) to decide whether a rebase with an imperfect agreement (i.e. the user's typed text is found in the suggestion but not at offset 0) should be accepted or rejected. This PR makes that limit configurable via an experiment setting so we can tune it without a code change.

Changes

NesRebaseConfigs interface (editRebase.ts)

• Added maxImperfectAgreementLength: number as a required field (non-optional, so call sites always supply an explicit value — no hidden fallbacks).
• Both places that enforce the strict limit now read directly from nesConfigs.maxImperfectAgreementLength:
  • Normal agreement path in agreementIndexOf
  • Reverse agreement path in tryRebaseEdits
• Default parameter values for the two public helpers (tryRebase, tryRebaseStringEdits) are set to { maxImperfectAgreementLength } (the existing constant, value 5), preserving current behaviour for callers that don't pass configs.

Config key (configurationService.ts)

• Added ConfigKey.TeamInternal.InlineEditsMaxImperfectAgreementLength — an experiment-based number setting with key chat.advanced.inlineEdits.maxImperfectAgreementLength and default 5.

Wire-up (nextEditCache.ts)

• _getNesRebaseConfigs() now reads the new key and includes it in the returned NesRebaseConfigs.

Telemetry / debug code (rebaseResult.ts)

• toReproductionTestCode() emits maxImperfectAgreementLength in the generated nesConfigs snippet when it is set.

Tests (editRebase.spec.ts)

• All existing nesConfigs object literals updated to include maxImperfectAgreementLength (using the imported constant) to satisfy the now-required field.

[Copilot]

Pull request overview

This PR makes the tryRebase “imperfect agreement” conflict threshold configurable via an experiment-backed setting, replacing the previously hard-coded maxImperfectAgreementLength = 5 limit so it can be tuned without code changes.

Changes:

• Adds an experiment-based config key chat.advanced.inlineEdits.maxImperfectAgreementLength (default 5).
• Wires the setting into NES rebase logic by making maxImperfectAgreementLength a required field of NesRebaseConfigs and using it in both agreement paths.
• Updates rebase debugging output and unit tests to include the new required config field.

Show a summary per file

File	Description
extensions/copilot/src/platform/configuration/common/configurationService.ts	Adds new experiment-based team-internal config key for the threshold.
extensions/copilot/src/extension/inlineEdits/node/nextEditCache.ts	Reads the new config and supplies it in NesRebaseConfigs.
extensions/copilot/src/extension/inlineEdits/common/editRebase.ts	Makes the threshold required in NesRebaseConfigs and uses it in strict rejection logic; adds defaulting in public helpers.
extensions/copilot/src/extension/inlineEdits/node/rebaseResult.ts	Includes the new config in auto-generated reproduction test output.
extensions/copilot/src/extension/inlineEdits/test/common/editRebase.spec.ts	Updates test config objects to include maxImperfectAgreementLength.

Copilot's findings

Comments suppressed due to low confidence (2)

extensions/copilot/src/extension/inlineEdits/node/rebaseResult.ts:136

• Same as above: since maxImperfectAgreementLength is required, this ternary will always append , nesConfigs even when no optional flags are enabled. If you only want to pass nesConfigs when it meaningfully differs from defaults, gate on that instead of !== undefined.

		const configsArg = (this.nesRebaseConfigs.absorbSubsequenceTyping || this.nesRebaseConfigs.reverseAgreement || this.nesRebaseConfigs.maxImperfectAgreementLength !== undefined) ? ', nesConfigs' : '';
		lines.push(`\texpect(tryRebase(originalDocument, editWindow, originalEdits, [], userEditSince, currentDocumentContent, currentSelection, 'strict', logger${configsArg})).toMatchInlineSnapshot();`);

extensions/copilot/src/extension/inlineEdits/common/editRebase.ts:144

• tryRebaseStringEdits has the same issue as tryRebase: the default nesConfigs = { maxImperfectAgreementLength } can throw at runtime in circular-import scenarios because maxImperfectAgreementLength is initialized later in the module. Define the constant before these exported functions (or otherwise ensure it's initialized before use).

export function tryRebaseStringEdits<T extends IEditData<T>>(content: string, ours: StringEdit, base: StringEdit, resolution: 'strict' | 'lenient', nesConfigs: NesRebaseConfigs = { maxImperfectAgreementLength }): StringEdit | undefined {
	return tryRebaseEdits(content, ours.mapData(r => new VoidEditData()), base, resolution, nesConfigs)?.toStringEdit();

• Files reviewed: 5/5 changed files
• Comments generated: 5