runconfig: set task default shell

Currently, if no shell is defined in the task and in the step, the executor will
use an hardcoded default shell.

This will cause changed run behavior if we add an option to globally set the
agola default shell.

To avoid this set the task shell to the default shell inside the runconfig if
it's empty so future executions will always use this value.

internal/runconfig/runconfig.go

@@ -26,6 +26,10 @@ import (
 	errors "golang.org/x/xerrors"
 )
 
+const (
+	defaultShell = "/bin/sh -e"
+)
+
 func genRuntime(c *config.Config, ce *config.Runtime, variables map[string]string) *rstypes.Runtime {
 	containers := []*rstypes.Container{}
 	for _, cc := range ce.Containers {
@@ -206,6 +210,10 @@ func GenRunConfigTasks(uuid util.UUIDGenerator, c *config.Config, runName string
 			DockerRegistriesAuth: make(map[string]rstypes.DockerRegistryAuth),
 		}
 
+		if t.Shell == "" {
+			t.Shell = defaultShell
+		}
+
 		if c.DockerRegistriesAuth != nil {
 			for regname, auth := range c.DockerRegistriesAuth {
 				t.DockerRegistriesAuth[regname] = rstypes.DockerRegistryAuth{

internal/runconfig/runconfig_test.go

@@ -801,6 +801,7 @@ func TestGenRunConfig(t *testing.T) {
 							},
 						},
 					},
+					Shell: "/bin/sh -e",
 					Environment: map[string]string{
 						"ENV01":             "ENV01",
 						"ENVFROMVARIABLE01": "VARVALUE01",
@@ -876,6 +877,7 @@ func TestGenRunConfig(t *testing.T) {
 							},
 						},
 					},
+					Shell:       "/bin/sh -e",
 					Environment: map[string]string{},
 					Steps: rstypes.Steps{
 						&rstypes.RunStep{BaseStep: rstypes.BaseStep{Type: "run", Name: "command01"}, Command: "command01", Environment: map[string]string{}},
@@ -973,6 +975,7 @@ func TestGenRunConfig(t *testing.T) {
 							},
 						},
 					},
+					Shell:       "/bin/sh -e",
 					Environment: map[string]string{},
 					Steps: rstypes.Steps{
 						&rstypes.RunStep{BaseStep: rstypes.BaseStep{Type: "run", Name: "command01"}, Command: "command01", Environment: map[string]string{}},

internal/services/executor/executor.go

@@ -109,6 +109,8 @@ func (e *Executor) doRunStep(ctx context.Context, s *types.RunStep, t *types.Exe
 	}
 	defer outf.Close()
 
+	// TODO(sgotti) this line is used only for old runconfig versions that don't
+	// set a task default shell in the runconfig
 	shell := defaultShell
 	if t.Shell != "" {
 		shell = t.Shell