feat: skip pulling an already cloned plan when CI is set

README.md

@@ -204,6 +204,25 @@ export SHUTTLE_CACHE_DURATION_MIN=60 # Cache a plan for 60 minutes
 This feature caches pr. repo, as such the cache isn't shared between working
 repositories.
 
+#### Skipping the pull
+
+Every shuttle invocation pulls the plan again, which is wasted time in CI where
+the plan was just cloned and cannot have changed during the job. Shuttle
+therefore skips pulling an already cloned plan when the `CI` environment
+variable is set, as most CI systems do.
+
+Use `SHUTTLE_SKIP_PULL` to control this explicitly. It takes precedence over
+`CI`, so it can also force pulling back on:
+
+```bash
+export SHUTTLE_SKIP_PULL=true  # never pull an already cloned plan
+export SHUTTLE_SKIP_PULL=false # always pull, even when CI is set
+```
+
+The `--skip-pull` flag does the same for a single invocation. Note that none of
+these prevent the initial clone; a plan that isn't available locally yet is
+always cloned.
+
 ### Overloading the plan
 
 It is possible to overload the plan specified in `shuttle.yaml` file by using

pkg/git/git.go

@@ -29,6 +29,34 @@ var gitRegex = regexp.MustCompile(
 
 const cacheDurationMinKey = "SHUTTLE_CACHE_DURATION_MIN"
 
+const skipPullKey = "SHUTTLE_SKIP_PULL"
+
+// skipPullFromEnv reports whether plan pulling should be skipped based on the
+// environment. SHUTTLE_SKIP_PULL is the explicit opt in and takes precedence,
+// so it can also force pulling back on with a falsy value. Otherwise CI is
+// honoured, as CI jobs start from a fresh clone and pulling the plan again on
+// every shuttle invocation only costs time.
+func skipPullFromEnv(uii *ui.UI) bool {
+	if v, ok := os.LookupEnv(skipPullKey); ok {
+		skip, err := strconv.ParseBool(v)
+		if err != nil {
+			uii.Verboseln("%s is not a boolean, treating '%s' as false", skipPullKey, v)
+			return false
+		}
+		if skip {
+			uii.Verboseln("Skipping git plan pulling because %s=%s", skipPullKey, v)
+		}
+		return skip
+	}
+
+	if os.Getenv("CI") != "" {
+		uii.Verboseln("Skipping git plan pulling because CI is set")
+		return true
+	}
+
+	return false
+}
+
 func ParsePlan(plan string) Plan {
 	if !gitRegex.MatchString(plan) {
 		return Plan{
@@ -121,6 +149,9 @@ func GetGitPlan(
 				uii.Verboseln("Skipping git plan pulling")
 				return planPath, nil
 			}
+			if skipPullFromEnv(uii) {
+				return planPath, nil
+			}
 			valid, err := cacheIsValid(planPath)
 			if err != nil {
 				return "", err
@@ -172,7 +203,7 @@ func GetGitPlan(
 			if cloneToken != "" {
 				uii.Verboseln("Found clone token in env, but shuttle path was ssh-based. This override will not work.")
 			}
-			
+
 			cloneArg = parsedGitPlan.User + "@" + parsedGitPlan.Repository
 		} else {
 			panic(fmt.Sprintf("Unknown protocol '%s'", parsedGitPlan.Protocol))

pkg/git/skip_pull_test.go

@@ -0,0 +1,86 @@
+package git
+
+import (
+	"io"
+	"os"
+	"testing"
+
+	"github.com/lunarway/shuttle/pkg/ui"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSkipPullFromEnv(t *testing.T) {
+	tt := []struct {
+		name      string
+		skipPull  *string
+		ci        *string
+		skipsPull bool
+	}{
+		{
+			name:      "nothing set",
+			skipsPull: false,
+		},
+		{
+			name:      "CI set",
+			ci:        strPtr("true"),
+			skipsPull: true,
+		},
+		{
+			name:      "CI set to any non-empty value",
+			ci:        strPtr("1"),
+			skipsPull: true,
+		},
+		{
+			name:      "CI set but empty",
+			ci:        strPtr(""),
+			skipsPull: false,
+		},
+		{
+			name:      "SHUTTLE_SKIP_PULL set",
+			skipPull:  strPtr("true"),
+			skipsPull: true,
+		},
+		{
+			name:      "SHUTTLE_SKIP_PULL set but empty is treated as false",
+			skipPull:  strPtr(""),
+			skipsPull: false,
+		},
+		{
+			name:      "SHUTTLE_SKIP_PULL takes precedence over CI",
+			skipPull:  strPtr("false"),
+			ci:        strPtr("true"),
+			skipsPull: false,
+		},
+		{
+			name:      "SHUTTLE_SKIP_PULL with an unparsable value is treated as false",
+			skipPull:  strPtr("yes-please"),
+			skipsPull: false,
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			// Unset by default so the developer's own environment does not leak
+			// into the test.
+			t.Setenv(skipPullKey, "")
+			os.Unsetenv(skipPullKey)
+			t.Setenv("CI", "")
+			os.Unsetenv("CI")
+
+			if tc.skipPull != nil {
+				t.Setenv(skipPullKey, *tc.skipPull)
+			}
+			if tc.ci != nil {
+				t.Setenv("CI", *tc.ci)
+			}
+
+			uii := ui.Create(io.Discard, io.Discard)
+
+			assert.Equal(t, tc.skipsPull, skipPullFromEnv(uii))
+		})
+	}
+}
+
+func strPtr(s string) *string {
+	return &s
+}