Add way to gen one sig

Makefile

@@ -1,12 +1,15 @@
 all: \
-	build-sigdocs \
+	build-image \
-	run-sigdocs \
+	gen-docs \
 
 reset-docs:
 	git checkout HEAD -- sig-list.md sig-*
 
-build-sigdocs:
+build-image:
 	docker build -t sigdocs -f generator/Dockerfile generator
 
-run-sigdocs:
+gen-doc:
+	docker run -e SIG=${SIG} -v $(shell pwd):/go/src/app sigdocs
+
+gen-docs:
 	docker run -v $(shell pwd):/go/src/app sigdocs

generator/README.md

@@ -17,6 +17,15 @@ To (re)build documentation for all the SIGs, run these commands:
 make all
 ```
 
+To build docs for one SIG, run these commands:
+
+```bash
+make SIG=sig-apps gen-doc
+make SIG=sig-testing gen-doc
+```
+
+where the `SIG` var refers to the directory being built.
+
 ## Adding custom content to your SIG's README
 
 If your SIG wishes to add custom content, you can do so by placing it within

generator/app.go

@@ -179,9 +179,15 @@ func writeLastGenerated(f *os.File) {
 }
 
 func createReadmeFiles(ctx SigEntries) error {
+	selectedSig := os.Getenv("SIG")
 	for _, sig := range ctx.Sigs {
 		dirName := fmt.Sprintf("sig-%s", strings.ToLower(strings.Replace(sig.Name, " ", "-", -1)))
 
+		if selectedSig != "" && selectedSig != dirName {
+			fmt.Printf("Skipping %s\n", dirName)
+			continue
+		}
+
 		createDirIfNotExists(dirName)
 
 		prefix := sig.Contact.GithubTeamPrefix