Support repo license (#24872)

Close #278
Close #24076

## Solutions:
- Use
[google/licenseclassifier](https://github.com/google/licenseclassifier/)
Test result between
[google/licensecheck](https://github.com/google/licensecheck) and
[go-license-detector](https://github.com/go-enry/go-license-detector):
https://github.com/go-gitea/gitea/pull/24872#issuecomment-1560361167
Test result between
[google/licensecheck](https://github.com/google/licensecheck) and
[google/licenseclassifier](https://github.com/google/licenseclassifier/):
https://github.com/go-gitea/gitea/pull/24872#issuecomment-1576092178
- Generate License Convert Name List to avoid import license templates
with same contents
Gitea automatically get latest license data from[
spdx/license-list-data](https://github.com/spdx/license-list-data).
But unfortunately, some license templates have same contents. #20915
[click here to see the
list](https://github.com/go-gitea/gitea/pull/24872#issuecomment-1584141684)
So we will generate a list of these license templates with same contents
and create a new file to save the result when using `make
generate-license`. (Need to decide the save path)
- Save License info into a new table `repo_license`
Can easily support searching repo by license in the future.

## Screen shot
Single License:

![image](https://github.com/go-gitea/gitea/assets/18380374/41260bd7-0b4c-4038-8592-508706cffa9f)

Multiple Licenses:

![image](https://github.com/go-gitea/gitea/assets/18380374/34ce2f73-7e18-446b-9b96-ecc4fb61bd70)

Triggers:
- [x] Push commit to default branch
- [x] Create repo
- [x] Mirror repo
- [x] When Default Branch is changed, licenses should be updated

Todo:
- [x] Save Licenses info in to DB when there's a change to license file
in the commit
- [x] DB Migration
- [x] A nominal test?
- [x] Select which library to
use(https://github.com/go-gitea/gitea/pull/24872#issuecomment-1560361167)
- [x] API Support
- [x] Add repo license table
- ~Select license in settings if there are several licenses(Not
recommended)~
- License board(later, not in this PR)

![image](https://github.com/go-gitea/gitea/assets/18380374/2c3c3bf8-bcc2-4c6d-8ce0-81d1a9733878)

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Denys Konovalov <kontakt@denyskon.de>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: 6543 <m.huber@kithara.com>
Co-authored-by: a1012112796 <1012112796@qq.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.com>

1 files changed, 73 insertions, 0 deletions

diff --git a/services/repository/license_test.go b/services/repository/license_test.go
new file mode 100644
index 0000000000..39e9738145
--- /dev/null
+++ b/services/repository/license_test.go
@@ -0,0 +1,73 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package repository
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	repo_module "code.gitea.io/gitea/modules/repository"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_detectLicense(t *testing.T) {
+	type DetectLicenseTest struct {
+		name string
+		arg  string
+		want []string
+	}
+
+	tests := []DetectLicenseTest{
+		{
+			name: "empty",
+			arg:  "",
+			want: nil,
+		},
+		{
+			name: "no detected license",
+			arg:  "Copyright (c) 2023 Gitea",
+			want: nil,
+		},
+	}
+
+	repo_module.LoadRepoConfig()
+	err := loadLicenseAliases()
+	assert.NoError(t, err)
+	for _, licenseName := range repo_module.Licenses {
+		license, err := repo_module.GetLicense(licenseName, &repo_module.LicenseValues{
+			Owner: "Gitea",
+			Email: "teabot@gitea.io",
+			Repo:  "gitea",
+			Year:  "2024",
+		})
+		assert.NoError(t, err)
+
+		tests = append(tests, DetectLicenseTest{
+			name: fmt.Sprintf("single license test: %s", licenseName),
+			arg:  string(license),
+			want: []string{ConvertLicenseName(licenseName)},
+		})
+	}
+
+	err = InitLicenseClassifier()
+	assert.NoError(t, err)
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			license, err := detectLicense(strings.NewReader(tt.arg))
+			assert.NoError(t, err)
+			assert.Equal(t, tt.want, license)
+		})
+	}
+
+	result, err := detectLicense(strings.NewReader(tests[2].arg + tests[3].arg + tests[4].arg))
+	assert.NoError(t, err)
+	t.Run("multiple licenses test", func(t *testing.T) {
+		assert.Equal(t, 3, len(result))
+		assert.Contains(t, result, tests[2].want[0])
+		assert.Contains(t, result, tests[3].want[0])
+		assert.Contains(t, result, tests[4].want[0])
+	})
+}