refactor(gitea): eliminate retry duplication, harden redactURL and MaxInt64 edge case

- Extract doGetWithReader to share retry/backoff logic between doGet and
  doGetLimited, eliminating ~60 lines of duplicated code (addresses MINOR
  finding from all reviewers).
- redactURL now strips userinfo credentials (user:pass@host) in addition
  to query parameters (addresses security-review-bot finding).
- GetPullRequestDiff treats MaxDiffSize == math.MaxInt64 as disabled,
  preventing the silent enforcement bypass where the overflow clamp makes
  the size check unreachable (addresses security-review-bot finding).
- Improved error message wording: 'response exceeds N bytes' (NIT fix).

gitea/client.go

@@ -70,7 +70,8 @@ type Client struct {
 	RetryBackoff []time.Duration
 
 	// MaxDiffSize is the maximum number of bytes allowed when fetching a PR diff.
-	// If zero, defaults to DefaultMaxDiffSize (10 MB). Set to any negative value to disable the limit.
+	// If zero, defaults to DefaultMaxDiffSize (10 MB). Set to any negative value
+	// (or math.MaxInt64) to disable the limit.
 	//
 	// This field must be configured before the first request is made.
 	// Modifying it while requests are in flight is not safe.
@@ -149,8 +150,10 @@ func (c *Client) GetPullRequestDiff(ctx context.Context, owner, repo string, num
 		maxSize = DefaultMaxDiffSize
 	}
 
-	// When the limit is disabled, use the standard doGet path.
-	if maxSize < 0 {
+	// When the limit is disabled (negative) or set to math.MaxInt64 (which
+	// would overflow the +1 detection and silently disable enforcement),
+	// use the standard unlimited doGet path.
+	if maxSize < 0 || maxSize == math.MaxInt64 {
 		body, err := c.doGet(ctx, reqURL)
 		if err != nil {
 			return "", fmt.Errorf("fetch diff: %w", err)
@@ -323,9 +326,9 @@ func isRetriableSyscallError(err error) bool {
 	return true
 }
 
-// redactURL strips query parameters from a URL for safe logging.
-// This prevents accidental exposure of sensitive data that future callers
-// might pass via query strings.
+// redactURL strips query parameters and userinfo credentials from a URL for
+// safe logging. This prevents accidental exposure of sensitive data (tokens in
+// query strings, or user:pass in the authority) in log output.
 func redactURL(rawURL string) string {
 	parsed, err := url.Parse(rawURL)
 	if err != nil {
@@ -333,6 +336,9 @@ func redactURL(rawURL string) string {
 		// potentially logging something sensitive.
 		return "[invalid URL]"
 	}
+	if parsed.User != nil {
+		parsed.User = url.User("REDACTED")
+	}
 	if parsed.RawQuery != "" {
 		parsed.RawQuery = "[redacted]"
 	}
@@ -353,10 +359,12 @@ func sanitizeErrorForLog(err error) string {
 	return err.Error()
 }
 
-// doGet performs an HTTP GET request with retry on 5xx errors and temporary
-// network errors. Retries up to 3 times with exponential backoff (1s, 2s delays
-// by default; configurable via Client.RetryBackoff for testing).
-func (c *Client) doGet(ctx context.Context, reqURL string) ([]byte, error) {
+// doGetWithReader performs an HTTP GET request with retry on 5xx errors and
+// temporary network errors. Retries up to 3 times with exponential backoff
+// (1s, 2s delays by default; configurable via Client.RetryBackoff for testing).
+// The readBody function is called with the response body on success (2xx) and
+// is responsible for reading and closing it.
+func (c *Client) doGetWithReader(ctx context.Context, reqURL string, readBody func(io.ReadCloser) ([]byte, error)) ([]byte, error) {
 	const maxAttempts = 3
 	// backoff[i] is the delay before attempt i+1 (i.e., after attempt i fails).
 	// First attempt (i=0) has no delay; retries wait 1s then 2s by default.
@@ -421,12 +429,7 @@ func (c *Client) doGet(ctx context.Context, reqURL string) ([]byte, error) {
 			return nil, lastErr
 		}
 		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
-			body, err := io.ReadAll(resp.Body)
-			resp.Body.Close()
-			if err != nil {
-				return nil, err
-			}
-			return body, nil
+			return readBody(resp.Body)
 		}
 
 		// Error path: limit how much we read from potentially malicious server
@@ -444,90 +447,37 @@ func (c *Client) doGet(ctx context.Context, reqURL string) ([]byte, error) {
 	return nil, lastErr
 }
 
-// doGetLimited performs an HTTP GET request with retry (like doGet) but enforces
-// a maximum response body size. Returns ErrDiffTooLarge if the response exceeds
-// maxBytes. It reads maxBytes+1 (clamped to avoid overflow) to detect truncation
-// without buffering the entire body.
+// doGet performs an HTTP GET request with retry, reading the full response body.
+func (c *Client) doGet(ctx context.Context, reqURL string) ([]byte, error) {
+	return c.doGetWithReader(ctx, reqURL, func(body io.ReadCloser) ([]byte, error) {
+		defer body.Close()
+		return io.ReadAll(body)
+	})
+}
+
+// doGetLimited performs an HTTP GET request with retry but enforces a maximum
+// response body size. Returns ErrDiffTooLarge if the response exceeds maxBytes.
+// It reads maxBytes+1 (clamped to avoid overflow) to detect truncation without
+// buffering the entire body.
 func (c *Client) doGetLimited(ctx context.Context, reqURL string, maxBytes int64) ([]byte, error) {
-	const maxAttempts = 3
-	backoff := c.RetryBackoff
-	if backoff == nil {
-		backoff = []time.Duration{1 * time.Second, 2 * time.Second}
-	}
-	const maxErrorBodyBytes = 64 * 1024
-
-	var lastErr error
-	for attempt := 0; attempt < maxAttempts; attempt++ {
-		if attempt > 0 {
-			var delay time.Duration
-			if attempt-1 < len(backoff) {
-				delay = backoff[attempt-1]
-			}
-			if delay > 0 {
-				slog.Warn("retrying request after error",
-					"attempt", attempt+1,
-					"url", redactURL(reqURL),
-					"delay", delay.String(),
-					"lastError", sanitizeErrorForLog(lastErr))
-
-				timer := time.NewTimer(delay)
-				select {
-				case <-timer.C:
-				case <-ctx.Done():
-					timer.Stop()
-					return nil, ctx.Err()
-				}
-			}
-		}
-
-		req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
-		if err != nil {
-			return nil, err
-		}
-		req.Header.Set("Authorization", "token "+c.token)
-
-		resp, err := c.http.Do(req)
-		if err != nil {
-			lastErr = err
-			if attempt < maxAttempts-1 && isTemporaryNetError(err) {
-				slog.Warn("temporary network error, will retry",
-					"attempt", attempt+1,
-					"url", redactURL(reqURL),
-					"error", err)
-				continue
-			}
-			return nil, lastErr
-		}
-		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
+	return c.doGetWithReader(ctx, reqURL, func(body io.ReadCloser) ([]byte, error) {
+		defer body.Close()
 		// Read up to maxBytes+1 to detect overflow.
 		// Clamp to prevent integer overflow when maxBytes == math.MaxInt64.
 		limitBytes := maxBytes + 1
 		if limitBytes <= 0 {
 			limitBytes = math.MaxInt64
 		}
-			limited := io.LimitReader(resp.Body, limitBytes)
-			body, err := io.ReadAll(limited)
-			resp.Body.Close()
+		limited := io.LimitReader(body, limitBytes)
+		data, err := io.ReadAll(limited)
 		if err != nil {
 			return nil, err
 		}
-			if int64(len(body)) > maxBytes {
-				return nil, fmt.Errorf("%w: response is larger than %d bytes", ErrDiffTooLarge, maxBytes)
+		if int64(len(data)) > maxBytes {
+			return nil, fmt.Errorf("%w: response exceeds %d bytes", ErrDiffTooLarge, maxBytes)
 		}
-			return body, nil
-		}
-
-		errBody, _ := io.ReadAll(io.LimitReader(resp.Body, maxErrorBodyBytes))
-		resp.Body.Close()
-
-		lastErr = &APIError{StatusCode: resp.StatusCode, Body: string(errBody)}
-
-		if resp.StatusCode < 500 || resp.StatusCode >= 600 {
-			return nil, lastErr
-		}
-	}
-
-	return nil, lastErr
+		return data, nil
+	})
 }
 
 // escapePath escapes each segment of a relative file path for use in URLs.

gitea/client_test.go

@@ -1092,6 +1092,21 @@ func TestRedactURL(t *testing.T) {
 			input: "",
 			want:  "",
 		},
+		{
+			name:  "with userinfo - redacts credentials",
+			input: "https://admin:secret@gitea.example.com/api/v1/repos",
+			want:  "https://REDACTED@gitea.example.com/api/v1/repos",
+		},
+		{
+			name:  "with userinfo and query params",
+			input: "https://user:pass@example.com/path?token=abc",
+			want:  "https://REDACTED@example.com/path?[redacted]",
+		},
+		{
+			name:  "username only - no password",
+			input: "https://user@example.com/path",
+			want:  "https://REDACTED@example.com/path",
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

gitea/diff_size_test.go

@@ -3,6 +3,7 @@ package gitea
 import (
 	"context"
 	"errors"
+	"math"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -48,6 +49,12 @@ func TestGetPullRequestDiff_SizeLimits(t *testing.T) {
 			maxDiffSize: -1,
 			wantDiff:    strings.Repeat("x", 10000),
 		},
+		{
+			name:        "math.MaxInt64 treated as disabled",
+			diff:        strings.Repeat("x", 10000),
+			maxDiffSize: math.MaxInt64,
+			wantDiff:    strings.Repeat("x", 10000),
+		},
 		{
 			name:        "default limit",
 			diff:        "diff content",