fix: error when --remote flag used with repo argument

When a repository argument is provided to `gh repo fork`, the command
operates independently of the current local repository. Using --remote
in this context is incompatible because there's no local repository to
add the remote to.

This change returns an explicit error when these flags are combined,
providing clear feedback instead of silently ignoring the --remote flag.

Fixes #2722

Signed-off-by: majiayu000 <1835304752@qq.com>

pkg/cmd/repo/fork/fork.go

@@ -113,6 +113,10 @@ func NewCmdFork(f *cmdutil.Factory, runF func(*ForkOptions) error) *cobra.Comman
 				opts.Rename = true // Any existing 'origin' will be renamed to upstream
 			}
 
+			if opts.Repository != "" && cmd.Flags().Changed("remote") {
+				return cmdutil.FlagErrorf("the `--remote` flag is unsupported when a repository argument is provided")
+			}
+
 			if promptOk {
 				// We can prompt for these if they were not specified.
 				opts.PromptClone = !cmd.Flags().Changed("clone")

pkg/cmd/repo/fork/fork_test.go

@@ -144,6 +144,12 @@ func TestNewCmdFork(t *testing.T) {
 				Rename:     false,
 			},
 		},
+		{
+			name:    "remote with repo argument",
+			cli:     "foo/bar --remote",
+			wantErr: true,
+			errMsg:  "the `--remote` flag is unsupported when a repository argument is provided",
+		},
 	}
 
 	for _, tt := range tests {