Fixing as per @Armels comments

Signed-off-by: Mohammed Zeeshan Ahmed <mohammed.zee1000@gmail.com>

pkg/init/backend/flags.go

@@ -52,7 +52,11 @@ func (o *FlagsBackend) Validate(flags map[string]string, fs filesystem.Filesyste
 		}
 		registries := o.preferenceClient.RegistryList()
 		for _, r := range *registries {
-			if r.Name == flags[FLAG_DEVFILE_REGISTRY] && util.IsGithubBasedRegistry(r.URL) {
+			isGithubRegistry, err := util.IsGithubBasedRegistry(r.URL)
+			if err != nil {
+				return err
+			}
+			if r.Name == flags[FLAG_DEVFILE_REGISTRY] && isGithubRegistry {
 				return util.ErrGithubRegistryNotSupported
 			}
 		}

pkg/odo/cli/preference/registry/add.go

@@ -73,7 +73,11 @@ func (o *AddOptions) Validate() (err error) {
 	if err != nil {
 		return err
 	}
-	if util2.IsGithubBasedRegistry(o.registryURL) {
+	isGithubRegistry, err := util2.IsGithubBasedRegistry(o.registryURL)
+	if err != nil {
+		return err
+	}
+	if isGithubRegistry {
 		return util2.ErrGithubRegistryNotSupported
 	}
 	return nil

pkg/odo/cli/preference/registry/update.go

@@ -71,7 +71,11 @@ func (o *UpdateOptions) Validate() (err error) {
 	if err != nil {
 		return err
 	}
-	if registryUtil.IsGithubBasedRegistry(o.registryURL) {
+	isGithubBasedRegistry, err := registryUtil.IsGithubBasedRegistry(o.registryURL)
+	if err != nil {
+		return err
+	}
+	if isGithubBasedRegistry {
 		return registryUtil.ErrGithubRegistryNotSupported
 	}
 	return nil

pkg/odo/cli/preference/registry/util/util.go

@@ -4,9 +4,11 @@ import (
 	// odo packages
 
 	"errors"
+	"fmt"
 	"strings"
 
 	"github.com/redhat-developer/odo/pkg/preference"
+	url2 "net/url"
 )
 
 const (
@@ -30,6 +32,10 @@ func IsSecure(prefClient preference.Client, registryName string) bool {
 	return isSecure
 }
 
-func IsGithubBasedRegistry(url string) bool {
-	return strings.Contains(url, "github.com") || strings.Contains(url, "raw.githubusercontent.com")
+func IsGithubBasedRegistry(url string) (bool, error) {
+	pu, err := url2.Parse(url)
+	if err != nil {
+		return false, fmt.Errorf("unable to parse registry url %w", err)
+	}
+	return strings.Contains(pu.Host, "github.com") || strings.Contains(url, "raw.githubusercontent.com"), nil
 }

pkg/odo/cli/preference/registry/util/util_test.go

@@ -91,11 +91,20 @@ func TestIsGitBasedRegistry(t *testing.T) {
 			registryURL: "https://raw.githubusercontent.com/odo-devfiles/registry",
 			want:        true,
 		},
+		{
+			name:        "Case 4: Returns false if URL contains github.com in a non-host position",
+			registryURL: "https://my.registry.example.com/github.com",
+			want:        false,
+		},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			if actual := IsGithubBasedRegistry(tt.registryURL); actual != tt.want {
+			actual, err := IsGithubBasedRegistry(tt.registryURL)
+			if err != nil {
+				t.Errorf("unexpected error %s occoured", err.Error())
+			}
+			if actual != tt.want {
 				t.Errorf("failed checking if registry is git based, got %t want %t", actual, tt.want)
 			}
 		})

pkg/registry/registry.go

@@ -133,7 +133,11 @@ func (o RegistryClient) ListDevfileStacks(registryName string) (DevfileStackList
 
 // getRegistryStacks retrieves the registry's index devfile stack entries
 func getRegistryStacks(preferenceClient preference.Client, registry Registry) ([]DevfileStack, error) {
-	if registryUtil.IsGithubBasedRegistry(registry.URL) {
+	isGithubregistry, err := registryUtil.IsGithubBasedRegistry(registry.URL)
+	if err != nil {
+		return nil, err
+	}
+	if isGithubregistry {
 		return nil, registryUtil.ErrGithubRegistryNotSupported
 	}
 	// OCI-based registry