Add clobber flag to alias set (#7787)

pkg/cmd/alias/set/set.go

@@ -17,9 +17,10 @@ type SetOptions struct {
 	Config func() (config.Config, error)
 	IO     *iostreams.IOStreams
 
-	Name      string
-	Expansion string
-	IsShell   bool
+	Name              string
+	Expansion         string
+	IsShell           bool
+	OverwriteExisting bool
 
 	validAliasName      func(string) bool
 	validAliasExpansion func(string) bool
@@ -86,6 +87,7 @@ func NewCmdSet(f *cmdutil.Factory, runF func(*SetOptions) error) *cobra.Command
 	}
 
 	cmd.Flags().BoolVarP(&opts.IsShell, "shell", "s", false, "Declare an alias to be passed through a shell interpreter")
+	cmd.Flags().BoolVar(&opts.OverwriteExisting, "clobber", false, "Overwrite existing aliases of the same name")
 
 	return cmd
 }
@@ -104,31 +106,39 @@ func setRun(opts *SetOptions) error {
 		return fmt.Errorf("did not understand expansion: %w", err)
 	}
 
+	if opts.IsShell && !strings.HasPrefix(expansion, "!") {
+		expansion = "!" + expansion
+	}
+
 	isTerminal := opts.IO.IsStdoutTTY()
 	if isTerminal {
-		fmt.Fprintf(opts.IO.ErrOut, "- Adding alias for %s: %s\n", cs.Bold(opts.Name), cs.Bold(expansion))
+		fmt.Fprintf(opts.IO.ErrOut, "- Creating alias for %s: %s\n", cs.Bold(opts.Name), cs.Bold(expansion))
 	}
 
-	if opts.IsShell && !strings.HasPrefix(expansion, "!") {
-		expansion = "!" + expansion
+	var existingAlias bool
+	if _, err := aliasCfg.Get(opts.Name); err == nil {
+		existingAlias = true
 	}
 
 	if !opts.validAliasName(opts.Name) {
-		return fmt.Errorf("could not create alias: %q is already a gh command, extension, or alias", opts.Name)
-	}
+		if !existingAlias {
+			return fmt.Errorf("%s Could not create alias %s: already a gh command or extension",
+				cs.FailureIcon(),
+				cs.Bold(opts.Name))
+		}
 
-	if !opts.validAliasExpansion(expansion) {
-		return fmt.Errorf("could not create alias: %s does not correspond to a gh command, extension, or alias", expansion)
+		if existingAlias && !opts.OverwriteExisting {
+			return fmt.Errorf("%s Could not create alias %s: name already taken, use the --clobber flag to overwrite it",
+				cs.FailureIcon(),
+				cs.Bold(opts.Name),
+			)
+		}
 	}
 
-	successMsg := fmt.Sprintf("%s Added alias.", cs.SuccessIcon())
-	if oldExpansion, err := aliasCfg.Get(opts.Name); err == nil {
-		successMsg = fmt.Sprintf("%s Changed alias %s from %s to %s",
-			cs.SuccessIcon(),
-			cs.Bold(opts.Name),
-			cs.Bold(oldExpansion),
-			cs.Bold(expansion),
-		)
+	if !opts.validAliasExpansion(expansion) {
+		return fmt.Errorf("%s Could not create alias %s: expansion does not correspond to a gh command, extension, or alias",
+			cs.FailureIcon(),
+			cs.Bold(opts.Name))
 	}
 
 	aliasCfg.Add(opts.Name, expansion)
@@ -138,6 +148,13 @@ func setRun(opts *SetOptions) error {
 		return err
 	}
 
+	successMsg := fmt.Sprintf("%s Added alias %s", cs.SuccessIcon(), cs.Bold(opts.Name))
+	if existingAlias && opts.OverwriteExisting {
+		successMsg = fmt.Sprintf("%s Changed alias %s",
+			cs.WarningIcon(),
+			cs.Bold(opts.Name))
+	}
+
 	if isTerminal {
 		fmt.Fprintln(opts.IO.ErrOut, successMsg)
 	}