Feat: add Support of Terratag parameters through Environment Variable

README.md

@@ -175,6 +175,19 @@ locals {
 - `-filter=<regular expression>` - defaults to `.*`. Only apply tags to the resource types matched by the regular expression
 - `-type=<terraform or terragrunt>` - defaults to `terraform`. If `terragrunt` is used, tags the files under `.terragrunt-cache` folder. Note: if Terragrunt does not create a `.terragrunt-cache` folder, use the default or omit.
 
+Setting options via enviroment variables is also supported. CLI flags have a precedence over envrionment variable.
+
+```
+TERRATAG_TAGS
+TERRATAG_DIR
+TERRATAG_SKIPTERRATAGFILES
+TERRATAG_FILTER
+TERRATAG_SKIP
+TERRATAG_VERBOSE
+TERRATAG_RENAME
+TERRATAG_TYPE
+```
+
 ##### See more samples [here](https://github.com/env0/terratag/tree/master/test/fixture)
 
 ## Notes

cli/args.go

@@ -5,6 +5,7 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"strings"
 
 	"github.com/env0/terratag/internal/common"
 )
@@ -48,6 +49,21 @@ func InitArgs() (Args, error) {
 	fs.StringVar(&args.Type, "type", string(common.Terraform), "The IAC type. Valid values: terraform or terragrunt")
 	fs.BoolVar(&args.Version, "version", false, "Prints the version")
 
+	// Set cli args based on environment variables.
+	//The command line flags have precedence over environment variables.
+	fs.VisitAll(func(f *flag.Flag) {
+		if f.Name == "version" {
+			return
+		}
+
+		name := "TERRATAG_" + strings.ToUpper(strings.ReplaceAll(f.Name, "-", "_"))
+		if value, ok := os.LookupEnv(name); ok {
+			if err := fs.Set(f.Name, value); err != nil {
+				fmt.Printf("[WARN] failed to set command arg flag '%s' from environment variable '%s': %v\n", f.Name, name, err)
+			}
+		}
+	})
+
 	if err := fs.Parse(programArgs); err != nil {
 		return args, err
 	}

terratag_test.go

@@ -15,10 +15,12 @@ import (
 
 	"github.com/bmatcuk/doublestar"
 	"github.com/env0/terratag/cli"
+	"github.com/env0/terratag/internal/common"
 	. "github.com/onsi/gomega"
 	"github.com/otiai10/copy"
 	"github.com/spf13/viper"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 var cleanArgs = append([]string(nil), os.Args...)
@@ -397,3 +399,49 @@ func TestToHclMap(t *testing.T) {
 		})
 	}
 }
+
+func TestEnvVariables(t *testing.T) {
+	os.Setenv("TERRATAG_TAGS", `{"a":"b"}`)
+	os.Setenv("TERRATAG_DIR", "./dir")
+	os.Setenv("TERRATAG_SKIPTERRATAGFILES", "true")
+	os.Setenv("TERRATAG_FILTER", "filter")
+	os.Setenv("TERRATAG_SKIP", "skip")
+	os.Setenv("TERRATAG_VERBOSE", "true")
+	os.Setenv("TERRATAG_RENAME", "false")
+	os.Setenv("TERRATAG_TYPE", string(common.Terragrunt))
+
+	defer func() {
+		os.Unsetenv("TERRATAG_TAGS")
+		os.Unsetenv("TERRATAG_DIR")
+		os.Unsetenv("TERRATAG_SKIPTERRATAGFILES")
+		os.Unsetenv("TERRATAG_FILTER")
+		os.Unsetenv("TERRATAG_SKIP")
+		os.Unsetenv("TERRATAG_VERBOSE")
+		os.Unsetenv("TERRATAG_RENAME")
+		os.Unsetenv("TERRATAG_TYPE")
+	}()
+
+	osArgsLock.Lock()
+	defer osArgsLock.Unlock()
+
+	os.Args = []string{programName}
+	args, err := cli.InitArgs()
+	os.Args = cleanArgs
+	require.Nil(t, err)
+
+	assert.Equal(t, `{"a":"b"}`, args.Tags)
+	assert.Equal(t, "./dir", args.Dir)
+	assert.Equal(t, true, args.IsSkipTerratagFiles)
+	assert.Equal(t, "filter", args.Filter)
+	assert.Equal(t, "skip", args.Skip)
+	assert.Equal(t, true, args.Verbose)
+	assert.Equal(t, false, args.Rename)
+	assert.Equal(t, string(common.Terragrunt), args.Type)
+
+	// The command line flags have precedence over environment variables.
+	os.Args = []string{programName, `-tags={"c":"d"}`}
+	args, err = cli.InitArgs()
+	os.Args = cleanArgs
+	require.Nil(t, err)
+	assert.Equal(t, `{"c":"d"}`, args.Tags)
+}