Detect fish shell

Signed-off-by: Jean-Laurent de Morlhon <jeanlaurent@morlhon.net>

commands/env.go

@@ -261,5 +261,9 @@ func detectShell() (string, error) {
 		return "", ErrUnknownShell
 	}
 
+	if os.Getenv("__fish_bin_dir") != "" {
+		return "fish", nil
+	}
+
 	return shell, nil
 }

commands/env_test.go

@@ -547,3 +547,22 @@ func TestShellCfgUnset(t *testing.T) {
 		os.Setenv(test.noProxyVar, "")
 	}
 }
+
+func TestDetectBash(t *testing.T) {
+	original_shell := os.Getenv("SHELL")
+	os.Setenv("SHELL", "/bin/bash")
+	defer os.Setenv("SHELL", original_shell)
+	shell, _ := detectShell()
+	assert.Equal(t, "bash", shell)
+}
+
+func TestDetectFish(t *testing.T) {
+	original_shell := os.Getenv("SHELL")
+	os.Setenv("SHELL", "/bin/bash")
+	defer os.Setenv("SHELL", original_shell)
+	original_fishdir := os.Getenv("__fish_bin_dir")
+	os.Setenv("__fish_bin_dir", "/usr/local/Cellar/fish/2.2.0/bin")
+	defer os.Setenv("__fish_bin_dir", original_fishdir)
+	shell, _ := detectShell()
+	assert.Equal(t, "fish", shell)
+}