Apply semantic diffs to get_commit, get_diff, and get_files #1984

SamMorrowDrums · 2026-02-09T23:10:13Z

Summary

Integrates the semantic diff engine into the existing tools that return file patches, so models get more token-efficient diffs across all diff-producing tools — not just compare_file_contents.

Tools updated

Tool	Method	Change
`get_commit`	—	Adds `patch` field to each file in the response, with semantic diff applied
`pull_request_read`	`get_diff`	Splits multi-file raw diff by file, applies semantic diff per-file
`pull_request_read`	`get_files`	Applies semantic diff to each file's `patch` field

How it works

For each file patch, checks the file extension against known formats
Structured data (JSON, YAML, CSV, TOML): Reconstructs base/head from the patch hunks, produces path-based semantic diff
Code files (Go, Python, JS, etc.): Reconstructs base/head, produces structural declaration-level diff with inline detail
Other files: Keeps the original unified diff patch unchanged

Patch reconstruction

The reconstructFromPatch function extracts base and head content from unified diff hunks. This works well because:

Structured data files typically have the full content in the diff
Code patches include enough context for tree-sitter to parse declarations
If reconstruction fails or produces poor results, the original patch is preserved

Testing

10 unit tests for diff integration (patch reconstruction, per-file splitting, semantic application)
All existing tests pass unchanged
Lint clean

Dependencies

Stacked on #1983 (symbol extraction) → #1982 (tree-sitter) → #1981 (semantic data diffs)

Part of #1973

Integrates the semantic diff engine into existing tools that return file patches: - get_commit: Adds Patch field to MinimalCommitFile and applies semantic diff for supported formats (JSON, YAML, CSV, TOML) and structural diff for code files - pull_request_read (get_diff): Splits multi-file raw diff by file and applies semantic diff per-file where beneficial - pull_request_read (get_files): Applies semantic diff to each file's Patch field before returning Unsupported file types keep their original unified diff patches unchanged. Patches are reconstructed from hunks to feed the semantic diff engine — this works well for structured data where the full content is typically in the diff.

Copilot

Pull request overview

This PR integrates the existing semantic/structural diff engine into the remaining diff-producing GitHub MCP tools so they return more token-efficient patches (not just compare_file_contents). It post-processes per-file patches and multi-file PR diffs to apply semantic diffs where supported, while falling back to the original unified diff when not.

Changes:

pull_request_read.get_diff: post-processes the raw multi-file diff, splitting by file and applying semantic/structural diffs per file when beneficial.
pull_request_read.get_files: applies semantic/structural diffs to each file’s patch field when possible.
get_commit: adds a patch field to MinimalCommitFile and applies semantic/structural diffing to commit file patches.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
pkg/github/pullrequests.go	Applies semantic diff processing to PR raw diffs (`get_diff`) and file patches (`get_files`).
pkg/github/minimal_types.go	Adds `patch` to `MinimalCommitFile` and applies semantic diffing during minimal commit conversion.
pkg/github/diff_integration.go	Introduces helpers to reconstruct base/head from hunks, split multi-file diffs, and apply semantic diffs per file.
pkg/github/diff_integration_test.go	Adds unit tests for patch reconstruction, diff splitting, and semantic application behavior.

Comments suppressed due to low confidence (1)

pkg/github/pullrequests.go:300

This mutates each file's Patch to a semantic/structural diff when possible, but current get_files tests don't assert anything about the patch field or semantic transformation. Add coverage that includes a realistic patch body for a supported format and assert the marshaled response has the transformed patch for that file (and leaves unsupported formats unchanged).

	// Apply semantic diffs to file patches where beneficial
	for _, file := range files {
		if file.Patch != nil && file.Filename != nil {
			semanticPatch := applySemanticDiffToUnifiedPatch(file.GetFilename(), file.GetPatch())
			file.Patch = &semanticPatch

Copilot · 2026-02-09T23:15:00Z

pkg/github/diff_integration.go

+		}
+
+		semanticPatch := applySemanticDiffToUnifiedPatch(section.filename, section.patch)
+		if semanticPatch != section.patch {


When a per-file patch is converted to a semantic diff, the output drops the original per-file diff header (e.g., diff --git, index, new file mode, rename from/to, deleted file mode). This loses important metadata (notably renames and mode changes) and can make the result misleading. Preserve the original header information even when emitting a semantic/structural diff (or explicitly include any rename/mode metadata alongside the semantic diff).

Suggested change

if semanticPatch != section.patch {

if semanticPatch != section.patch {

// Preserve the original per-file header (including metadata such as renames/mode changes)

result.WriteString(section.header)

if section.header != "" {

result.WriteString("\n")

}

Copilot · 2026-02-09T23:15:00Z

pkg/github/pullrequests.go

+	// Return the raw response, with semantic diffs applied where beneficial
+	return utils.NewToolResultText(processMultiFileDiff(string(raw))), nil


This changes get_diff output by post-processing the raw multi-file diff, but existing pull request tests only cover a Markdown diff (which is expected to remain unchanged). Add a test case that includes at least one supported semantic/structural file type (e.g., JSON or Go) and assert that the returned diff is transformed accordingly, so regressions in semantic application/splitting are caught.

This issue also appears on line 296 of the same file.

Copilot · 2026-02-09T23:15:01Z

pkg/github/minimal_types.go

 			for _, file := range commit.Files {
+				patch := file.GetPatch()
+				if patch != "" {
+					patch = applySemanticDiffToUnifiedPatch(file.GetFilename(), patch)
+				}


MinimalCommitFile now includes a patch field and convertToMinimalCommit applies semantic/structural diffing to it. There doesn't appear to be test coverage asserting that get_commit returns the new patch field and that semantic diffing is applied (or that include_diff=false still omits diffs). Adding a focused test will help prevent accidental regressions in commit output.

Import declarations now show package names instead of opaque _import_declaration_N identifiers. Go imports extract short package names (e.g., 'fmt, http, context'). For large import blocks, shows first two and count (e.g., 'fmt, http, ... (5 packages)'). Import blocks are keyed by position rather than name, so changing the imported packages shows as 'modified' with inline diff instead of separate remove+add entries. Added declarations now show their signature (first line) to give context about what was added, rather than just the word 'added'.

…ed files Package clauses now extract the package name from the package_identifier child node, showing 'package handler' instead of '_package_clause_0'. New and deleted code files now show a declaration summary listing all top-level symbols with their signatures, rather than just 'file added' or 'file deleted'. This gives the model a table-of-contents view of what was added/removed.

Multi-var/const blocks now extract all declared names from var_spec_list children (e.g., 'globalMap, oldRegexp' instead of '_var_declaration_19'). For >3 names, shows first two plus count. Var/const blocks are keyed by position (like imports) so adding/removing a variable shows as 'modified' with inline diff rather than remove+add. When name extraction returns empty, falls back to showing the first line of the declaration text instead of opaque '_kind_N' indices. This ensures no tree-sitter internal names appear in output.

When searching for a symbol like 'RegisterRoutes', if no exact match is found, try suffix matching against receiver-qualified names like '(*Handler).RegisterRoutes'. Returns the match only when unambiguous (exactly one suffix match). Error messages now suggest the closest match when a suffix match exists but wasn't used (e.g., when there are multiple types with the same method name). Updated the symbol parameter description to document the receiver prefix format and note that bare names work when unambiguous.

SamMorrowDrums requested a review from a team as a code owner February 9, 2026 23:10

Copilot AI review requested due to automatic review settings February 9, 2026 23:10

Copilot started reviewing on behalf of SamMorrowDrums February 9, 2026 23:10 View session

Copilot AI reviewed Feb 9, 2026

View reviewed changes

SamMorrowDrums added 4 commits February 10, 2026 00:16

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Apply semantic diffs to get_commit, get_diff, and get_files #1984

Apply semantic diffs to get_commit, get_diff, and get_files #1984

Uh oh!

SamMorrowDrums commented Feb 9, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI Feb 9, 2026

Uh oh!

Copilot AI Feb 9, 2026

Uh oh!

Copilot AI Feb 9, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant

-		if semanticPatch != section.patch {
+		if semanticPatch != section.patch {
+			// Preserve the original per-file header (including metadata such as renames/mode changes)
+			result.WriteString(section.header)
+			if section.header != "" {
+				result.WriteString("\n")
+			}

		// Return the raw response, with semantic diffs applied where beneficial
		return utils.NewToolResultText(processMultiFileDiff(string(raw))), nil

Apply semantic diffs to get_commit, get_diff, and get_files #1984

Are you sure you want to change the base?

Apply semantic diffs to get_commit, get_diff, and get_files #1984

Uh oh!

Conversation

SamMorrowDrums commented Feb 9, 2026

Summary

Tools updated

How it works

Patch reconstruction

Testing

Dependencies

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Copilot AI Feb 9, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 9, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 9, 2026

Choose a reason for hiding this comment

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

1 participant