Support package-names with dashes in them (#232)

Support package-names with dashes in them

We were smart about aliasing if you have name-collisions, but not if
your package name is something that's not a valid identifier, like
`"path/to/my-package"`, which Go for better or worse allows. Now we
remove all the invalid characters (in practice mainly dashes, dots, and
leading digits).

Fixes #231.

Test plan: make check

generate/testdata/snapshots/TestGenerateWithConfig-CustomContextWithAlias-testdata-queries-generated.go

@@ -0,0 +1,68 @@
+// Code generated by github.com/Khan/genqlient, DO NOT EDIT.
+
+package queries
+
+import (
+	"context"
+
+	"github.com/Khan/genqlient/graphql"
+	junkfunname "github.com/Khan/genqlient/internal/testutil/junk---fun.name"
+)
+
+// Check that context_type from genqlient.yaml implements context.Context.
+var _ context.Context = (junkfunname.MyContext)(nil)
+
+// SimpleQueryResponse is returned by SimpleQuery on success.
+type SimpleQueryResponse struct {
+	// user looks up a user by some stuff.
+	//
+	// See UserQueryInput for what stuff is supported.
+	// If query is null, returns the current user.
+	User SimpleQueryUser `json:"user"`
+}
+
+// GetUser returns SimpleQueryResponse.User, and is useful for accessing the field via an interface.
+func (v *SimpleQueryResponse) GetUser() SimpleQueryUser { return v.User }
+
+// SimpleQueryUser includes the requested fields of the GraphQL type User.
+// The GraphQL type's documentation follows.
+//
+// A User is a user!
+type SimpleQueryUser struct {
+	// id is the user's ID.
+	//
+	// It is stable, unique, and opaque, like all good IDs.
+	Id string `json:"id"`
+}
+
+// GetId returns SimpleQueryUser.Id, and is useful for accessing the field via an interface.
+func (v *SimpleQueryUser) GetId() string { return v.Id }
+
+func SimpleQuery(
+	ctx junkfunname.MyContext,
+	client graphql.Client,
+) (*SimpleQueryResponse, error) {
+	req := &graphql.Request{
+		OpName: "SimpleQuery",
+		Query: `
+query SimpleQuery {
+	user {
+		id
+	}
+}
+`,
+	}
+	var err error
+
+	var data SimpleQueryResponse
+	resp := &graphql.Response{Data: &data}
+
+	err = client.MakeRequest(
+		ctx,
+		req,
+		resp,
+	)
+
+	return &data, err
+}
+