[gitea] Refactor parseSignatureFromCommitLine (#29054)

Replace #28849. Thanks to @yp05327 for the looking into the problem.
Fix #28840

The old behavior of newSignatureFromCommitline is not right. The new
parseSignatureFromCommitLine:

1. never fails
2. only accept one format (if there is any other, it could be easily added)

And add some tests.

(cherry picked from commit a24e1da7e9e38fc5f5c84c083d122c0cc3da4b74)

modules/git/signature_test.go

@@ -0,0 +1,47 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package git
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseSignatureFromCommitLine(t *testing.T) {
+	tests := []struct {
+		line string
+		want *Signature
+	}{
+		{
+			line: "a b <c@d.com> 12345 +0100",
+			want: &Signature{
+				Name:  "a b",
+				Email: "c@d.com",
+				When:  time.Unix(12345, 0).In(time.FixedZone("", 3600)),
+			},
+		},
+		{
+			line: "bad line",
+			want: &Signature{Name: "bad line"},
+		},
+		{
+			line: "bad < line",
+			want: &Signature{Name: "bad < line"},
+		},
+		{
+			line: "bad > line",
+			want: &Signature{Name: "bad > line"},
+		},
+		{
+			line: "bad-line <name@example.com>",
+			want: &Signature{Name: "bad-line <name@example.com>"},
+		},
+	}
+	for _, test := range tests {
+		got := parseSignatureFromCommitLine(test.line)
+		assert.EqualValues(t, test.want, got)
+	}
+}