FIX gogs migration if gogs is hosted at a subpath (#3572)

Also add a test for GogsDownloaderFactory.New() to make sure
that the URL of the source repository is parsed correctly.

When the source gogs instance is hosted at a subpath like `https://git.example.com/gogs/<username>/<reponame>` the migration fails.
This PR fixes that.

Co-authored-by: hecker <tomas.hecker@gmail.com>
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/3572
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: varp0n <tom@gkstn.de>
Co-committed-by: varp0n <tom@gkstn.de>

2 files changed, 95 insertions, 4 deletions

diff --git a/services/migrations/gogs.go b/services/migrations/gogs.go
index 72c52d180b..b31d05fa73 100644
--- a/services/migrations/gogs.go
+++ b/services/migrations/gogs.go
@@ -38,17 +38,24 @@ func (f *GogsDownloaderFactory) New(ctx context.Context, opts base.MigrateOption
 		return nil, err
 	}
 
-	baseURL := u.Scheme + "://" + u.Host
 	repoNameSpace := strings.TrimSuffix(u.Path, ".git")
 	repoNameSpace = strings.Trim(repoNameSpace, "/")
 
 	fields := strings.Split(repoNameSpace, "/")
-	if len(fields) < 2 {
+	numFields := len(fields)
+	if numFields < 2 {
 		return nil, fmt.Errorf("invalid path: %s", repoNameSpace)
 	}
 
-	log.Trace("Create gogs downloader. BaseURL: %s RepoOwner: %s RepoName: %s", baseURL, fields[0], fields[1])
-	return NewGogsDownloader(ctx, baseURL, opts.AuthUsername, opts.AuthPassword, opts.AuthToken, fields[0], fields[1]), nil
+	repoOwner := fields[numFields-2]
+	repoName := fields[numFields-1]
+
+	u.Path = ""
+	u = u.JoinPath(fields[:numFields-2]...)
+	baseURL := u.String()
+
+	log.Trace("Create gogs downloader. BaseURL: %s RepoOwner: %s RepoName: %s", baseURL, repoOwner, repoName)
+	return NewGogsDownloader(ctx, baseURL, opts.AuthUsername, opts.AuthPassword, opts.AuthToken, repoOwner, repoName), nil
 }
 
 // GitServiceType returns the type of git service
diff --git a/services/migrations/gogs_test.go b/services/migrations/gogs_test.go
index 610af183de..ca02b4317b 100644
--- a/services/migrations/gogs_test.go
+++ b/services/migrations/gogs_test.go
@@ -137,3 +137,87 @@ func TestGogsDownloadRepo(t *testing.T) {
 	_, _, err = downloader.GetPullRequests(1, 3)
 	assert.Error(t, err)
 }
+
+func TestGogsDownloaderFactory_New(t *testing.T) {
+	tests := []struct {
+		name      string
+		args      base.MigrateOptions
+		baseURL   string
+		repoOwner string
+		repoName  string
+		wantErr   bool
+	}{
+		{
+			name: "Gogs_at_root",
+			args: base.MigrateOptions{
+				CloneAddr:    "https://git.example.com/user/repo.git",
+				AuthUsername: "username",
+				AuthPassword: "password",
+				AuthToken:    "authtoken",
+			},
+			baseURL:   "https://git.example.com/",
+			repoOwner: "user",
+			repoName:  "repo",
+			wantErr:   false,
+		},
+		{
+			name: "Gogs_at_sub_path",
+			args: base.MigrateOptions{
+				CloneAddr:    "https://git.example.com/subpath/user/repo.git",
+				AuthUsername: "username",
+				AuthPassword: "password",
+				AuthToken:    "authtoken",
+			},
+			baseURL:   "https://git.example.com/subpath",
+			repoOwner: "user",
+			repoName:  "repo",
+			wantErr:   false,
+		},
+		{
+			name: "Gogs_at_2nd_sub_path",
+			args: base.MigrateOptions{
+				CloneAddr:    "https://git.example.com/sub1/sub2/user/repo.git",
+				AuthUsername: "username",
+				AuthPassword: "password",
+				AuthToken:    "authtoken",
+			},
+			baseURL:   "https://git.example.com/sub1/sub2",
+			repoOwner: "user",
+			repoName:  "repo",
+			wantErr:   false,
+		},
+		{
+			name: "Gogs_URL_too_short",
+			args: base.MigrateOptions{
+				CloneAddr:    "https://git.example.com/repo.git",
+				AuthUsername: "username",
+				AuthPassword: "password",
+				AuthToken:    "authtoken",
+			},
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			f := &GogsDownloaderFactory{}
+			opts := base.MigrateOptions{
+				CloneAddr:    tt.args.CloneAddr,
+				AuthUsername: tt.args.AuthUsername,
+				AuthPassword: tt.args.AuthPassword,
+				AuthToken:    tt.args.AuthToken,
+			}
+			got, err := f.New(context.Background(), opts)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("GogsDownloaderFactory.New() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			} else if err != nil {
+				return
+			}
+
+			assert.IsType(t, &GogsDownloader{}, got)
+			assert.EqualValues(t, tt.baseURL, got.(*GogsDownloader).baseURL)
+			assert.EqualValues(t, tt.repoOwner, got.(*GogsDownloader).repoOwner)
+			assert.EqualValues(t, tt.repoName, got.(*GogsDownloader).repoName)
+		})
+	}
+}