feat: full file context + patterns-repo support

Major improvements to review quality:

1. Full file context: fetch complete content of all modified files from
   the PR branch and include as reference. This eliminates false-positive
   "missing import" findings since the model sees the entire file.

2. Patterns repo: new --patterns-repo / PATTERNS_REPO flag fetches
   language idiom files from a separate Gitea repo (e.g. rodin/elixir-patterns)
   and includes them as review criteria.

3. Multi-file patterns: --patterns-files / PATTERNS_FILES accepts
   comma-separated file paths to fetch from the patterns repo.

New API methods:
- GetPullRequestFiles: list changed files in a PR
- GetFileContentRef: fetch file content from a specific branch/ref

Prompt changes:
- BuildSystemPrompt now accepts (conventions, patterns)
- BuildUserPrompt now accepts fileContext parameter
- File context displayed before diff for model reference
- Patterns presented as "review criteria" in system prompt

Composite action updated with patterns-repo and patterns-files inputs.

.gitea/actions/review/action.yml

@@ -37,6 +37,14 @@ inputs:
     description: 'Path to conventions file in the repo (e.g. CLAUDE.md)'
     required: false
     default: ''
+  patterns-repo:
+    description: 'Repo with language patterns (e.g. rodin/elixir-patterns)'
+    required: false
+    default: ''
+  patterns-files:
+    description: 'Comma-separated file paths to fetch from patterns repo'
+    required: false
+    default: 'README.md'
   temperature:
     description: 'LLM temperature (0 = server default)'
     required: false
@@ -123,6 +131,8 @@ runs:
         LLM_API_KEY: ${{ inputs.llm-api-key }}
         LLM_MODEL: ${{ inputs.llm-model }}
         CONVENTIONS_FILE: ${{ inputs.conventions-file }}
+        PATTERNS_REPO: ${{ inputs.patterns-repo }}
+        PATTERNS_FILES: ${{ inputs.patterns-files }}
         LLM_TEMPERATURE: ${{ inputs.temperature }}
       run: |
         ARGS=""

cmd/review-bot/main.go

@@ -1,6 +1,5 @@
 package main
 
-
 import (
 	"flag"
 	"fmt"
@@ -27,6 +26,8 @@ func main() {
 	llmAPIKey := flag.String("llm-api-key", envOrDefault("LLM_API_KEY", ""), "LLM API key")
 	llmModel := flag.String("llm-model", envOrDefault("LLM_MODEL", ""), "LLM model name")
 	conventionsFile := flag.String("conventions-file", envOrDefault("CONVENTIONS_FILE", ""), "Conventions file path in repo (e.g. CLAUDE.md)")
+	patternsRepo := flag.String("patterns-repo", envOrDefault("PATTERNS_REPO", ""), "Repo with language patterns (e.g. rodin/elixir-patterns)")
+	patternsFiles := flag.String("patterns-files", envOrDefault("PATTERNS_FILES", "README.md"), "Comma-separated file paths to fetch from patterns repo")
 	dryRun := flag.Bool("dry-run", false, "Print review to stdout instead of posting")
 	llmTemp := flag.Float64("llm-temperature", envOrDefaultFloat("LLM_TEMPERATURE", 0), "LLM temperature (0 = server default)")
 
@@ -79,7 +80,17 @@ func main() {
 	}
 	log.Printf("Diff size: %d bytes", len(diff))
 
-	// Step 3: Check CI status
+	// Step 3: Fetch full file content for modified files
+	fileContext := ""
+	files, err := giteaClient.GetPullRequestFiles(owner, repoName, prNumber)
+	if err != nil {
+		log.Printf("Warning: could not fetch PR files list: %v", err)
+	} else {
+		fileContext = fetchFileContext(giteaClient, owner, repoName, pr.Head.Ref, files)
+		log.Printf("Fetched full context for %d files", len(files))
+	}
+
+	// Step 4: Check CI status
 	ciPassed := true
 	ciDetails := ""
 	if pr.Head.Sha != "" {
@@ -92,7 +103,7 @@ func main() {
 		}
 	}
 
-	// Step 4: Load conventions file if specified
+	// Step 5: Load conventions file if specified
 	conventions := ""
 	if *conventionsFile != "" {
 		content, err := giteaClient.GetFileContent(owner, repoName, *conventionsFile)
@@ -104,11 +115,18 @@ func main() {
 		}
 	}
 
-	// Step 5: Build prompts
-	systemPrompt := review.BuildSystemPrompt(conventions)
-	userPrompt := review.BuildUserPrompt(pr.Title, pr.Body, diff, ciPassed, ciDetails)
+	// Step 6: Load patterns from external repo if specified
+	patterns := ""
+	if *patternsRepo != "" {
+		patterns = fetchPatterns(giteaClient, *patternsRepo, *patternsFiles)
+		log.Printf("Loaded patterns from %s (%d bytes)", *patternsRepo, len(patterns))
+	}
 
-	// Step 6: Call LLM
+	// Step 7: Build prompts
+	systemPrompt := review.BuildSystemPrompt(conventions, patterns)
+	userPrompt := review.BuildUserPrompt(pr.Title, pr.Body, diff, fileContext, ciPassed, ciDetails)
+
+	// Step 8: Call LLM
 	log.Printf("Sending to LLM (%s)...", *llmModel)
 	messages := []llm.Message{
 		{Role: "system", Content: systemPrompt},
@@ -121,14 +139,14 @@ func main() {
 	}
 	log.Printf("LLM response received (%d bytes)", len(response))
 
-	// Step 7: Parse response
+	// Step 9: Parse response
 	result, err := review.ParseResponse(response)
 	if err != nil {
 		log.Fatalf("Failed to parse LLM response: %v", err)
 	}
 	log.Printf("Verdict: %s (%d findings)", result.Verdict, len(result.Findings))
 
-	// Step 8: Format and post review
+	// Step 10: Format and post review
 	reviewBody := review.FormatMarkdown(result, *reviewerName)
 	event := review.GiteaEvent(result.Verdict)
 
@@ -146,6 +164,51 @@ func main() {
 	log.Printf("Review posted successfully!")
 }
 
+// fetchFileContext fetches the full content of modified files from the PR branch.
+func fetchFileContext(client *gitea.Client, owner, repo, ref string, files []gitea.ChangedFile) string {
+	var sb strings.Builder
+	for _, f := range files {
+		if f.Status == "removed" {
+			continue // Skip deleted files
+		}
+		content, err := client.GetFileContentRef(owner, repo, f.Filename, ref)
+		if err != nil {
+			log.Printf("Warning: could not fetch %s: %v", f.Filename, err)
+			continue
+		}
+		sb.WriteString(fmt.Sprintf("--- %s ---\n", f.Filename))
+		sb.WriteString("```\n")
+		sb.WriteString(content)
+		sb.WriteString("\n```\n\n")
+	}
+	return sb.String()
+}
+
+// fetchPatterns fetches pattern files from an external repo.
+func fetchPatterns(client *gitea.Client, patternsRepo, patternsFiles string) string {
+	parts := strings.SplitN(patternsRepo, "/", 2)
+	if len(parts) != 2 {
+		log.Printf("Warning: invalid patterns-repo format %q, expected owner/name", patternsRepo)
+		return ""
+	}
+	owner, repo := parts[0], parts[1]
+
+	var sb strings.Builder
+	for _, filepath := range strings.Split(patternsFiles, ",") {
+		filepath = strings.TrimSpace(filepath)
+		if filepath == "" {
+			continue
+		}
+		content, err := client.GetFileContent(owner, repo, filepath)
+		if err != nil {
+			log.Printf("Warning: could not fetch pattern file %s from %s: %v", filepath, patternsRepo, err)
+			continue
+		}
+		sb.WriteString(fmt.Sprintf("### %s/%s\n\n%s\n\n", patternsRepo, filepath, content))
+	}
+	return sb.String()
+}
+
 // evaluateCIStatus checks if all CI statuses indicate success.
 func evaluateCIStatus(statuses []gitea.CommitStatus) (passed bool, details string) {
 	if len(statuses) == 0 {

gitea/client.go

@@ -26,10 +26,11 @@ func NewClient(baseURL, token string) *Client {
 
 // PullRequest holds relevant PR metadata.
 type PullRequest struct {
-	Title  string `json:"title"`
-	Body   string `json:"body"`
-	Head   struct {
+	Title string `json:"title"`
+	Body  string `json:"body"`
+	Head  struct {
 		Sha string `json:"sha"`
+		Ref string `json:"ref"`
 	} `json:"head"`
 }
 
@@ -41,6 +42,12 @@ type CommitStatus struct {
 	TargetURL   string `json:"target_url"`
 }
 
+// ChangedFile represents a file modified in a PR.
+type ChangedFile struct {
+	Filename string `json:"filename"`
+	Status   string `json:"status"`
+}
+
 // GetPullRequest fetches PR metadata.
 func (c *Client) GetPullRequest(owner, repo string, number int) (*PullRequest, error) {
 	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d", c.BaseURL, owner, repo, number)
@@ -65,6 +72,20 @@ func (c *Client) GetPullRequestDiff(owner, repo string, number int) (string, err
 	return string(body), nil
 }
 
+// GetPullRequestFiles fetches the list of files changed in a PR.
+func (c *Client) GetPullRequestFiles(owner, repo string, number int) ([]ChangedFile, error) {
+	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/files", c.BaseURL, owner, repo, number)
+	body, err := c.doGet(url)
+	if err != nil {
+		return nil, fmt.Errorf("fetch PR files: %w", err)
+	}
+	var files []ChangedFile
+	if err := json.Unmarshal(body, &files); err != nil {
+		return nil, fmt.Errorf("parse PR files JSON: %w", err)
+	}
+	return files, nil
+}
+
 // GetCommitStatuses fetches CI statuses for a commit SHA.
 func (c *Client) GetCommitStatuses(owner, repo, sha string) ([]CommitStatus, error) {
 	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/commits/%s/statuses", c.BaseURL, owner, repo, sha)
@@ -89,6 +110,16 @@ func (c *Client) GetFileContent(owner, repo, filepath string) (string, error) {
 	return string(body), nil
 }
 
+// GetFileContentRef fetches a file from a specific ref (branch/tag/sha) in a repo.
+func (c *Client) GetFileContentRef(owner, repo, filepath, ref string) (string, error) {
+	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/raw/%s?ref=%s", c.BaseURL, owner, repo, filepath, ref)
+	body, err := c.doGet(url)
+	if err != nil {
+		return "", fmt.Errorf("fetch file %s@%s: %w", filepath, ref, err)
+	}
+	return string(body), nil
+}
+
 // PostReview submits a review to a PR.
 // event should be "APPROVED" or "REQUEST_CHANGES".
 func (c *Client) PostReview(owner, repo string, number int, event, body string) error {

gitea/client_test.go

@@ -193,3 +193,48 @@ func TestGetFileContent(t *testing.T) {
 		t.Errorf("expected %q, got %q", expected, got)
 	}
 }
+
+func TestGetPullRequestFiles(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/api/v1/repos/owner/repo/pulls/1/files" {
+			t.Errorf("unexpected path: %s", r.URL.Path)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.Write([]byte(`[{"filename":"main.go","status":"modified"},{"filename":"old.go","status":"removed"}]`))
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "test-token")
+	files, err := client.GetPullRequestFiles("owner", "repo", 1)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if len(files) != 2 {
+		t.Fatalf("expected 2 files, got %d", len(files))
+	}
+	if files[0].Filename != "main.go" || files[0].Status != "modified" {
+		t.Errorf("unexpected first file: %+v", files[0])
+	}
+}
+
+func TestGetFileContentRef(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/api/v1/repos/owner/repo/raw/main.go" {
+			t.Errorf("unexpected path: %s", r.URL.Path)
+		}
+		if r.URL.Query().Get("ref") != "feature-branch" {
+			t.Errorf("unexpected ref: %s", r.URL.Query().Get("ref"))
+		}
+		w.Write([]byte("package main\n"))
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "test-token")
+	content, err := client.GetFileContentRef("owner", "repo", "main.go", "feature-branch")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if content != "package main\n" {
+		t.Errorf("unexpected content: %q", content)
+	}
+}

review/prompt.go

@@ -6,15 +6,14 @@ import (
 )
 
 // BuildSystemPrompt constructs the system prompt for the LLM reviewer.
-func BuildSystemPrompt(conventions string) string {
+func BuildSystemPrompt(conventions, patterns string) string {
 	var sb strings.Builder
 
 	sb.WriteString("You are an expert code reviewer. Review the provided pull request diff carefully.\n\n")
-	sb.WriteString("IMPORTANT CONTEXT:\n")
-	sb.WriteString("- You are reviewing a DIFF, not the complete file. Code not shown in the diff already exists in the repository.\n")
-	sb.WriteString("- Imports, type definitions, functions, and other declarations that do not appear in the diff are already present in the file.\n")
-	sb.WriteString("- Do NOT flag missing imports, missing type definitions, or undefined references unless the diff itself introduces a new usage without a corresponding addition in the same diff.\n")
-	sb.WriteString("- Only flag issues with code that is actually being ADDED or MODIFIED in this diff.\n\n")
+	sb.WriteString("CONTEXT:\n")
+	sb.WriteString("- You will receive the full content of modified files for reference, followed by the diff showing what changed.\n")
+	sb.WriteString("- The diff shows ONLY what was added/removed. The full file content provides complete context.\n")
+	sb.WriteString("- Focus your review on the CHANGES (the diff), using the full files for context.\n\n")
 	sb.WriteString("Your task:\n")
 	sb.WriteString("1. Review the diff for correctness, idiomatic code, potential bugs, and design issues.\n")
 	sb.WriteString("2. Consider the CI status — if CI has failed, that is an automatic REQUEST_CHANGES regardless of code quality.\n")
@@ -40,17 +39,20 @@ func BuildSystemPrompt(conventions string) string {
 	sb.WriteString("- Be thorough but fair. Don't nitpick style unless it impacts readability significantly.\n")
 	sb.WriteString("- Line numbers should reference the new file line numbers from the diff headers.\n")
 	sb.WriteString("- If the diff is empty or trivial (only formatting/whitespace), APPROVE with no findings.\n")
-	sb.WriteString("- Never flag 'missing imports' or 'undefined' errors for symbols that could exist in the unchanged portions of the file.\n")
+
+	if patterns != "" {
+		sb.WriteString(fmt.Sprintf("\n\n## Language Patterns & Idioms\n\nUse the following patterns as review criteria. Code that violates these established patterns is a finding:\n\n%s\n", patterns))
+	}
 
 	if conventions != "" {
-		sb.WriteString(fmt.Sprintf("\n\nThe repository has the following coding conventions that should be respected:\n\n%s\n", conventions))
+		sb.WriteString(fmt.Sprintf("\n\n## Repository Conventions\n\nThe repository has the following coding conventions that must be respected:\n\n%s\n", conventions))
 	}
 
 	return sb.String()
 }
 
 // BuildUserPrompt constructs the user message with PR context.
-func BuildUserPrompt(title, description, diff string, ciPassed bool, ciDetails string) string {
+func BuildUserPrompt(title, description, diff, fileContext string, ciPassed bool, ciDetails string) string {
 	var sb strings.Builder
 
 	sb.WriteString(fmt.Sprintf("## Pull Request: %s\n\n", title))
@@ -69,7 +71,13 @@ func BuildUserPrompt(title, description, diff string, ciPassed bool, ciDetails s
 		sb.WriteString(fmt.Sprintf("CI Details: %s\n", ciDetails))
 	}
 
-	sb.WriteString("\n### Diff\n\n")
+	if fileContext != "" {
+		sb.WriteString("\n### Full File Context (modified files)\n\n")
+		sb.WriteString(fileContext)
+		sb.WriteString("\n")
+	}
+
+	sb.WriteString("\n### Diff (changes to review)\n\n")
 	sb.WriteString("```diff\n")
 	sb.WriteString(diff)
 	sb.WriteString("\n```\n")

review/prompt_test.go

@@ -6,7 +6,7 @@ import (
 )
 
 func TestBuildSystemPrompt_NoConventions(t *testing.T) {
-	prompt := BuildSystemPrompt("")
+	prompt := BuildSystemPrompt("", "")
 
 	if !strings.Contains(prompt, "expert code reviewer") {
 		t.Error("expected system prompt to mention code reviewer role")
@@ -18,7 +18,7 @@ func TestBuildSystemPrompt_NoConventions(t *testing.T) {
 
 func TestBuildSystemPrompt_WithConventions(t *testing.T) {
 	conventions := "- Use stdlib only\n- No panics\n"
-	prompt := BuildSystemPrompt(conventions)
+	prompt := BuildSystemPrompt(conventions, "")
 
 	if !strings.Contains(prompt, "coding conventions") {
 		t.Error("expected conventions section")
@@ -29,7 +29,7 @@ func TestBuildSystemPrompt_WithConventions(t *testing.T) {
 }
 
 func TestBuildUserPrompt_Basic(t *testing.T) {
-	prompt := BuildUserPrompt("Fix bug", "Fixes the crash", "diff content here", true, "all checks passed")
+	prompt := BuildUserPrompt("Fix bug", "Fixes the crash", "diff content here", "", true, "all checks passed")
 
 	if !strings.Contains(prompt, "Fix bug") {
 		t.Error("expected PR title")
@@ -46,7 +46,7 @@ func TestBuildUserPrompt_Basic(t *testing.T) {
 }
 
 func TestBuildUserPrompt_CIFailed(t *testing.T) {
-	prompt := BuildUserPrompt("Add tests", "", "some diff", false, "lint: failed")
+	prompt := BuildUserPrompt("Add tests", "", "some diff", "", false, "lint: failed")
 
 	if !strings.Contains(prompt, "FAILED") {
 		t.Error("expected CI status FAILED")
@@ -57,7 +57,7 @@ func TestBuildUserPrompt_CIFailed(t *testing.T) {
 }
 
 func TestBuildUserPrompt_NoDescription(t *testing.T) {
-	prompt := BuildUserPrompt("Quick fix", "", "diff", true, "")
+	prompt := BuildUserPrompt("Quick fix", "", "diff", "", true, "")
 
 	if strings.Contains(prompt, "### Description") {
 		t.Error("should not contain Description header when body is empty")
@@ -66,7 +66,7 @@ func TestBuildUserPrompt_NoDescription(t *testing.T) {
 
 func TestBuildUserPrompt_DiffIncluded(t *testing.T) {
 	diff := "+func Hello() string {\n+\treturn \"hello\"\n+}"
-	prompt := BuildUserPrompt("Greeting", "Add greeting func", diff, true, "")
+	prompt := BuildUserPrompt("Greeting", "Add greeting func", diff, "", true, "")
 
 	if !strings.Contains(prompt, "```diff") {
 		t.Error("expected diff fence")
@@ -75,3 +75,44 @@ func TestBuildUserPrompt_DiffIncluded(t *testing.T) {
 		t.Error("expected diff content in prompt")
 	}
 }
+
+func TestBuildSystemPrompt_WithPatterns(t *testing.T) {
+	patterns := "## Naming: use snake_case for functions"
+	prompt := BuildSystemPrompt("", patterns)
+	if !strings.Contains(prompt, "Language Patterns") {
+		t.Error("expected patterns section header")
+	}
+	if !strings.Contains(prompt, "snake_case") {
+		t.Error("expected patterns content")
+	}
+}
+
+func TestBuildSystemPrompt_WithBoth(t *testing.T) {
+	conventions := "Run mix format before commit"
+	patterns := "Use pipe operator for transformations"
+	prompt := BuildSystemPrompt(conventions, patterns)
+	if !strings.Contains(prompt, "Repository Conventions") {
+		t.Error("expected conventions section")
+	}
+	if !strings.Contains(prompt, "Language Patterns") {
+		t.Error("expected patterns section")
+	}
+}
+
+func TestBuildUserPrompt_WithFileContext(t *testing.T) {
+	fileContext := "--- main.go ---\npackage main\n"
+	prompt := BuildUserPrompt("Fix", "desc", "diff here", fileContext, true, "")
+	if !strings.Contains(prompt, "Full File Context") {
+		t.Error("expected file context section")
+	}
+	if !strings.Contains(prompt, "package main") {
+		t.Error("expected file content in prompt")
+	}
+}
+
+func TestBuildUserPrompt_WithoutFileContext(t *testing.T) {
+	prompt := BuildUserPrompt("Fix", "desc", "diff here", "", true, "")
+	if strings.Contains(prompt, "Full File Context") {
+		t.Error("should not include file context section when empty")
+	}
+}