feat(vcs): complete Phase 1 — util.go, type cleanup, interface additions (fixes #84, #85, #86)

- Create vcs/util.go with GetAllFilesInPath and BuildLineToPositionMap
- Create vcs/util_test.go with comprehensive tests for both functions
- Remove review.ContentEntry type, replace with vcs.ContentEntry
- Remove review.GiteaClient interface, replace with vcs.FileReader
- Update review/repo_persona.go to use vcs.FileReader
- Update review/repo_persona_test.go to use vcs.ContentEntry
- Update cmd/review-bot/main.go adapter to implement vcs.FileReader
- Add Number and Base fields to vcs.PullRequest
- Add CommitStatus type to vcs/types.go
- Add GetFileContentAtRef to vcs.PRReader interface
- Add GetCommitStatuses to vcs.PRReader interface
- Add DismissReview to vcs.Reviewer interface
- Add stub implementations on gitea.Client for new interface methods

Closes #84, Closes #85, Closes #86

vcs/util.go

@@ -0,0 +1,145 @@
+package vcs
+
+import (
+	"context"
+	"fmt"
+	"strings"
+)
+
+// GetAllFilesInPath recursively fetches all file contents under a path using the
+// provided FileReader. Returns a map of filepath -> content for all files found.
+// If the path points to an empty directory, returns an empty map.
+func GetAllFilesInPath(ctx context.Context, client FileReader, owner, repo, path string) (map[string]string, error) {
+	results := make(map[string]string)
+
+	entries, err := client.ListContents(ctx, owner, repo, path)
+	if err != nil {
+		return nil, fmt.Errorf("list contents %q: %w", path, err)
+	}
+
+	for _, entry := range entries {
+		switch entry.Type {
+		case "file":
+			content, err := client.GetFileContent(ctx, owner, repo, entry.Path, "")
+			if err != nil {
+				return nil, fmt.Errorf("get file %q: %w", entry.Path, err)
+			}
+			results[entry.Path] = content
+		case "dir":
+			subResults, err := GetAllFilesInPath(ctx, client, owner, repo, entry.Path)
+			if err != nil {
+				return nil, fmt.Errorf("recurse into %q: %w", entry.Path, err)
+			}
+			for k, v := range subResults {
+				results[k] = v
+			}
+		}
+	}
+
+	return results, nil
+}
+
+// BuildLineToPositionMap parses a unified diff and returns a map of
+// filename -> (new line number -> diff position). The diff position is a
+// 1-indexed offset from the @@ hunk header line for each file.
+// Only lines that appear in the new file (context lines and additions) are mapped.
+// Deletion-only lines are not included.
+func BuildLineToPositionMap(diff string) map[string]map[int]int {
+	result := make(map[string]map[int]int)
+
+	lines := strings.Split(diff, "\n")
+	var currentFile string
+	var position int
+	var newLine int
+
+	for _, line := range lines {
+		// Detect new file in diff
+		if strings.HasPrefix(line, "+++ b/") {
+			currentFile = strings.TrimPrefix(line, "+++ b/")
+			position = 0
+			newLine = 0
+			if result[currentFile] == nil {
+				result[currentFile] = make(map[int]int)
+			}
+			continue
+		}
+
+		// Skip --- lines (old file header)
+		if strings.HasPrefix(line, "--- ") {
+			continue
+		}
+
+		// Skip diff --git lines
+		if strings.HasPrefix(line, "diff --git") {
+			continue
+		}
+
+		// Skip index lines
+		if strings.HasPrefix(line, "index ") {
+			continue
+		}
+
+		// Parse hunk headers
+		if strings.HasPrefix(line, "@@") {
+			position++
+			// Extract new file start line from @@ -a,b +c,d @@
+			newLine = parseHunkNewStart(line)
+			continue
+		}
+
+		// We need a current file to map lines
+		if currentFile == "" {
+			continue
+		}
+
+		// Process diff content lines
+		if strings.HasPrefix(line, "+") {
+			position++
+			result[currentFile][newLine] = position
+			newLine++
+		} else if strings.HasPrefix(line, "-") {
+			position++
+			// Deletion lines don't map to new line numbers
+		} else if strings.HasPrefix(line, " ") {
+			// Context line (space-prefixed)
+			if position > 0 {
+				position++
+				result[currentFile][newLine] = position
+				newLine++
+			}
+		}
+	}
+
+	return result
+}
+
+// parseHunkNewStart extracts the new-file starting line number from a hunk header.
+// Format: @@ -old_start[,old_count] +new_start[,new_count] @@
+func parseHunkNewStart(hunkLine string) int {
+	// Find the +N part
+	plusIdx := strings.Index(hunkLine, "+")
+	if plusIdx < 0 {
+		return 1
+	}
+	rest := hunkLine[plusIdx+1:]
+
+	// Read digits until comma or space
+	var numStr string
+	for _, ch := range rest {
+		if ch >= '0' && ch <= '9' {
+			numStr += string(ch)
+		} else {
+			break
+		}
+	}
+
+	if numStr == "" {
+		return 1
+	}
+
+	n := 0
+	for _, ch := range numStr {
+		n = n*10 + int(ch-'0')
+	}
+	return n
+}