refactor(seedspec): move seed spec parsing out of the campaign command

the campaign tool and the sweep tools that drive it have to read a seed specification the same way, or a sweep records an intent that differs from what ran. parseSeeds becomes seedspec.Parse with no behaviour change.

cmd/internal-tools/campaign/main.go

@@ -15,6 +15,8 @@ import (
 	"strings"
 	"syscall"
 	"time"
+
+	"github.com/priyanshujain/sanderling/internal/seedspec"
 )
 
 type config struct {
@@ -118,7 +120,7 @@ func parseArguments(arguments []string, stderr io.Writer) (config, error) {
 		return config{}, fmt.Errorf("--run-timeout %s must exceed --duration %s, or every run is killed before it finishes",
 			configuration.runTimeout, configuration.duration)
 	}
-	seeds, err := parseSeeds(seedSpecification)
+	seeds, err := seedspec.Parse(seedSpecification)
 	if err != nil {
 		return config{}, fmt.Errorf("--seeds: %w", err)
 	}

internal/seedspec/seeds.go

@@ -1,4 +1,8 @@
-package main
+// Package seedspec expands the seed specification a campaign is given into the
+// explicit list of seeds it intends to run. The campaign tool and the tools
+// that drive it have to read a specification the same way, or a sweep records
+// an intent that differs from what ran.
+package seedspec
 
 import (
 	"fmt"
@@ -6,9 +10,9 @@ import (
 	"strings"
 )
 
-// parseSeeds expands a seed specification such as "1-10,20,30-32" into the
+// Parse expands a seed specification such as "1-10,20,30-32" into the
 // explicit seed list a campaign intends to run.
-func parseSeeds(specification string) ([]int64, error) {
+func Parse(specification string) ([]int64, error) {
 	trimmed := strings.TrimSpace(specification)
 	if trimmed == "" {
 		return nil, fmt.Errorf("empty seed spec")

internal/seedspec/seeds_test.go

@@ -1,4 +1,4 @@
-package main
+package seedspec
 
 import (
 	"slices"
@@ -6,7 +6,7 @@ import (
 	"testing"
 )
 
-func TestParseSeeds_RangesAndLists(t *testing.T) {
+func TestParse_RangesAndLists(t *testing.T) {
 	cases := []struct {
 		specification string
 		want          []int64
@@ -18,7 +18,7 @@ func TestParseSeeds_RangesAndLists(t *testing.T) {
 		{"4-4", []int64{4}},
 	}
 	for _, testCase := range cases {
-		got, err := parseSeeds(testCase.specification)
+		got, err := Parse(testCase.specification)
 		if err != nil {
 			t.Fatalf("%q: %v", testCase.specification, err)
 		}
@@ -28,9 +28,9 @@ func TestParseSeeds_RangesAndLists(t *testing.T) {
 	}
 }
 
-func TestParseSeeds_RejectsSeedZero(t *testing.T) {
+func TestParse_RejectsSeedZero(t *testing.T) {
 	for _, specification := range []string{"0", "1,0,2", "0-3"} {
-		_, err := parseSeeds(specification)
+		_, err := Parse(specification)
 		if err == nil {
 			t.Fatalf("%q: expected rejection of seed 0", specification)
 		}
@@ -40,9 +40,9 @@ func TestParseSeeds_RejectsSeedZero(t *testing.T) {
 	}
 }
 
-func TestParseSeeds_RejectsMalformed(t *testing.T) {
+func TestParse_RejectsMalformed(t *testing.T) {
 	for _, specification := range []string{"", "   ", "abc", "1,,2", "5-1", "1-", "-5", "1-2-3", "1.5", "2,2"} {
-		if seeds, err := parseSeeds(specification); err == nil {
+		if seeds, err := Parse(specification); err == nil {
 			t.Errorf("%q: expected error, got %v", specification, seeds)
 		}
 	}