Add a option to force override module name

The module name is implied from the git repository name. However, both
r10k and puppet are very particular about module naming, and the
implicit rewrites rules can get in the way. Puppet will understand any
amount of dashes in the project name as `<vendor>-<module>`, rewriting
`-` to `/`. For git repositories, there are often arbitrary naming rules
with copious amounts of these control characters in repository names,
making it nearly impossible to serve both worlds at the same time.

This URL parameter (module_name) allows to override the module name
directly in the URL, ignoring the git repository name.

api/module.go

@@ -3,6 +3,7 @@ package api
 import (
 	"fmt"
 	"net/http"
+	"regexp"
 
 	"github.com/gin-gonic/gin"
 	log "github.com/sirupsen/logrus"
@@ -54,8 +55,21 @@ func (m ModuleController) DeployModule(c *gin.Context) {
 		cmd = append(cmd, branch)
 	}
 
+	module := data.ModuleName
+	overrideModule := c.Query("module_name")
+	// Restrictions to Puppet module names are: 1) begin with lowercase letter, 2) contain lowercase, digits or underscores
+	match, _ := regexp.MatchString("^[a-z][a-z0-9_]*$", overrideModule)
+	if !match {
+		c.JSON(http.StatusInternalServerError, gin.H{"message": "Invalid module name"})
+		c.Abort()
+		return
+	}
+	if overrideModule != "" {
+		module = overrideModule
+	}
+
 	// Append module name and r10k configuration to the cmd string slice
-	cmd = append(cmd, data.ModuleName)
+	cmd = append(cmd, module)
 	cmd = append(cmd, fmt.Sprintf("--config=%s", h.GetR10kConfig()))
 
 	// Set additional optional r10k flags if they are set