Add migration count check (#27)

Add checks for no matching of migration functions count and the length of `migrations` defined in `migrations.go`

For example, for `v284 -> v285`
![image](/attachments/e43c465e-d41f-4755-950d-d3565690ea2a)
remove line 556:
![image](/attachments/a8598239-f123-415a-8090-3bdb781ce6ab)
run `make lint-go-vet`:
![image](/attachments/7a55b7be-6c19-41b5-995f-98d4aa5a7100)

Reviewed-on: https://gitea.com/gitea/gitea-vet/pulls/27
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: yp05327 <576951401@qq.com>
Co-committed-by: yp05327 <576951401@qq.com>

checks/migrations.go

@@ -4,7 +4,9 @@
 package checks
 
 import (
+	"bufio"
 	"errors"
+	"os"
 	"os/exec"
 	"strings"
 
@@ -24,6 +26,8 @@ var (
 	migrationImpBlockList = []string{
 		"code.gitea.io/gitea/modules/structs",
 	}
+	migrationImpPrefix = "code.gitea.io/gitea/models/migrations/v"
+	migrationFile      = "migrations.go"
 )
 
 func checkMigrations(pass *analysis.Pass) (interface{}, error) {
@@ -56,13 +60,39 @@ func checkMigrations(pass *analysis.Pass) (interface{}, error) {
 	}
 
 	imps := strings.Split(string(impsOut), "\n")
+	migrationCount := 0
 	for _, imp := range imps {
 		if stringInSlice(imp, migrationImpBlockList) {
 			pass.Reportf(0, "code.gitea.io/gitea/models/migrations cannot import the following packages: %s", migrationImpBlockList)
 			return nil, nil
 		}
+
+		if strings.HasPrefix(imp, migrationImpPrefix) {
+			goFilesCmd := exec.Command("go", "list", "-f", `{{join .GoFiles "\n"}}`, imp)
+			goFilesOut, err := goFilesCmd.Output()
+			if err != nil {
+				return nil, err
+			}
+			// the last item is empty we need to ignore it
+			migrationCount += len(strings.Split(string(goFilesOut), "\n")) - 1
+		}
 	}
 
+	mf, err := os.Open(migrationFile)
+	if err != nil {
+		return nil, err
+	}
+	defer mf.Close()
+
+	l := bufio.NewScanner(mf)
+	for l.Scan() {
+		if strings.Contains(l.Text(), "NewMigration(\"") {
+			migrationCount--
+		}
+	}
+	if migrationCount != 0 {
+		pass.Reportf(0, "migration files count does not match migrations lengths in %s", migrationFile)
+	}
 	return nil, nil
 }