From ee8e3133a221a6ab7e0e737ad1df9b2ef3279f9b Mon Sep 17 00:00:00 2001
From: Runxi Yu
Date: Sat, 6 Jun 2026 21:56:49 +0000
Subject: object/signature: Detailed along with sentinel

---
 object/signature/parse.go | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/object/signature/parse.go b/object/signature/parse.go
index bb6f18ed..f8c1666e 100644
--- a/object/signature/parse.go
+++ b/object/signature/parse.go
@@ -3,6 +3,7 @@ package signature
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"strconv"
 
 	"lindenii.org/go/lgo/intconv"
@@ -17,12 +18,12 @@ var ErrInvalidSignature = errors.New("object/signature: invalid signature")
 func Parse(line []byte) (*Signature, error) {
 	lt := bytes.IndexByte(line, '<')
 	if lt < 0 {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: missing '<' before email", ErrInvalidSignature)
 	}
 
 	gtRel := bytes.IndexByte(line[lt+1:], '>')
 	if gtRel < 0 {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: missing '>' after email", ErrInvalidSignature)
 	}
 
 	gt := lt + 1 + gtRel
@@ -32,24 +33,24 @@ func Parse(line []byte) (*Signature, error) {
 
 	rest := line[gt+1:]
 	if len(rest) == 0 || rest[0] != ' ' {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: missing ' ' before timestamp", ErrInvalidSignature)
 	}
 
 	rest = rest[1:]
 
 	before, after, ok := bytes.Cut(rest, []byte{' '})
 	if !ok {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: missing ' ' between timestamp and timezone", ErrInvalidSignature)
 	}
 
 	when, err := strconv.ParseInt(string(before), 10, 64)
 	if err != nil {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: timestamp %q: %w", ErrInvalidSignature, before, err)
 	}
 
 	tz := after
 	if len(tz) < 5 {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: timezone %q is too short", ErrInvalidSignature, tz)
 	}
 
 	sign := 1
@@ -59,32 +60,32 @@ func Parse(line []byte) (*Signature, error) {
 		sign = -1
 	case '+':
 	default:
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: timezone sign %q is not '+' or '-'", ErrInvalidSignature, tz[0])
 	}
 
 	hh, err := strconv.Atoi(string(tz[1:3]))
 	if err != nil {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: timezone hour %q: %w", ErrInvalidSignature, tz[1:3], err)
 	}
 
 	mm, err := strconv.Atoi(string(tz[3:5]))
 	if err != nil {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: timezone minute %q: %w", ErrInvalidSignature, tz[3:5], err)
 	}
 
 	if hh < 0 || hh > 23 {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: timezone hour %d out of range", ErrInvalidSignature, hh)
 	}
 
 	if mm < 0 || mm > 59 {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: timezone minute %d out of range", ErrInvalidSignature, mm)
 	}
 
 	total := int64(hh)*60 + int64(mm)
 
 	offset, err := intconv.Int64ToInt32(total)
 	if err != nil {
-		return nil, ErrInvalidSignature
+		return nil, fmt.Errorf("%w: timezone offset out of range", ErrInvalidSignature)
 	}
 
 	if sign < 0 {
-- 
cgit v1.3.1-10-gc9f91