Add dry run mode

Having a dry run mode is very useful, e.g. in a CI/CD pipeline the dry
run mode can be run on feature branches and pull requests to verify that
the Gauge specs are in a valid state for publishing.  If they are not
valid then the CI/CD pipeline build can fail, alerting the submitter
of the pull request to amend them on the feature branch.  This ensures
that the Gauge specs are always in good shape to be automatically
published by the CI/CD pipeline upon any push to the trunk branch (e.g.
upon a successful pull request merge).

The dry run mode is set by setting a `DRY_RUN` environment variable
or property (we can't use a command-line flag for this as [Gauge does
not propagate command line flags to documentation plugins][1]).

[1]: getgauge/spectacle#42 (comment)

internal/confluence/publisher.go

@@ -47,16 +47,14 @@ func makeSpecsMap(m *gauge_messages.SpecDetails) map[string]Spec {
 func (p *Publisher) Publish(specPaths []string) {
 	var err error
 
-	logger.Infof(true, "Preparing to publish Gauge specs to Confluence ...")
+	logger.Infof(true, "Checking specs are in a valid state for publishing to Confluence ...")
 
 	err = p.space.setup()
 	if err != nil {
 		p.printFailureMessage(err)
 		return
 	}
 
-	logger.Infof(true, "Checking specs can be published ...")
-
 	for _, specPath := range specPaths {
 		err = p.dryRunChecks(specPath)
 		if err != nil {
@@ -65,8 +63,12 @@ func (p *Publisher) Publish(specPaths []string) {
 		}
 	}
 
-	logger.Infof(true, "Checking finished successfully ...")
+	if env.GetBoolean("DRY_RUN") {
+		logger.Infof(true, "Dry run finished successfully")
+		return
+	}
 
+	logger.Infof(true, "Checking finished successfully")
 	logger.Infof(true, "Publishing Gauge specs to Confluence ...")
 
 	err = p.space.deleteAllPagesExceptHomepage()

internal/env/env.go

@@ -4,6 +4,7 @@ package env
 import (
 	"fmt"
 	"os"
+	"strings"
 )
 
 // GetRequired returns an environment variable value or panics if not present.
@@ -16,3 +17,9 @@ func GetRequired(key string) string {
 
 	return value
 }
+
+// GetBoolean returns true if the environment variable exists and has a value of "true"
+func GetBoolean(key string) bool {
+	value := os.Getenv(key)
+	return strings.ToLower(value) == "true"
+}