Support a custom includes path (#25)

* Support a custom include path

cmd/mmake/mmake.go

@@ -37,7 +37,7 @@ func main() {
 	// ensure deps are installed
 	i := installer.New(installer.Config{
 		Resolver:    resolver.NewUniversalResolver(),
-		Destination: "/usr/local/include",
+		Destination: resolver.GetIncludePath(os.Args[1:]),
 		Log:         log.Log,
 		ForceUpdate: cmd == "update",
 	})

help/help.go

@@ -11,6 +11,7 @@ import (
 	"github.com/pkg/errors"
 
 	"github.com/tj/mmake/parser"
+	"github.com/tj/mmake/resolver"
 )
 
 // OutputAllShort outputs all short help representations to the given writer.
@@ -57,8 +58,8 @@ func OutputAllLong(r io.Reader, w io.Writer, targets []string) error {
 
 // getComments parses, filters, and sorts all comment nodes.
 func getComments(r io.Reader, targets []string) ([]parser.Comment, error) {
-	nodes, err := parser.ParseRecursive(r, "/usr/local/include")
-
+	nodes, err := parser.ParseRecursive(r, resolver.IncludePath)
+  
 	if err != nil {
 		return nil, errors.Wrap(err, "parsing")
 	}

resolver/resolver.go

@@ -5,6 +5,10 @@ import (
 	"io"
 )
 
+// DefaultIncludePath is the default directory where make includes reside and
+// to which mmake will download remote includes.
+const DefaultIncludePath = "/usr/local/include"
+
 // Errors.
 var (
 	// ErrNotFound is returned when a non-local lookup fails.
@@ -15,10 +19,30 @@ var (
 	ErrNotSupported = errors.New("unsupported")
 )
 
+// IncludePath is the directory where make includes reside and to which mmake
+// will download remote includes for the duration of a particular execution
+// of mmake.
+var IncludePath = DefaultIncludePath
+
 // Interface for resolving and fetching includes.
 type Interface interface {
 	// Get must return the contents of the file,
 	// ErrNotFound when the file is not found,
 	// or an error.
 	Get(path string) (io.ReadCloser, error)
 }
+
+// GetIncludePath allows the include path to be overridden.
+func GetIncludePath(args []string) string {
+	for idx, arg := range args {
+		if arg == "-I" && len(args) > idx+1 {
+			IncludePath = args[idx+1]
+			break
+		} else if arg[:2] == "-I" && len(arg) > 2 {
+			IncludePath = arg[2:]
+			break
+		}
+	}
+
+	return IncludePath
+}

resolver/resolver_test.go

@@ -7,6 +7,33 @@ import (
 	"github.com/tj/mmake/resolver"
 )
 
+func TestGetIncludePath(t *testing.T) {
+	var cases = []struct {
+		Args     []string
+		Expected string
+	}{
+		{[]string{}, resolver.DefaultIncludePath},
+		{[]string{"update", "-I", "./relative/path"}, "./relative/path"},
+		{[]string{"update", "-I./other/path"}, "./other/path"},
+		{[]string{"update", "-I./other/path", "-I", "multiple/"}, "./other/path"},
+		{[]string{"-I", "multiple/"}, "multiple/"},
+		{[]string{"-I"}, resolver.DefaultIncludePath},
+		{[]string{"update"}, resolver.DefaultIncludePath},
+	}
+
+	for _, c := range cases {
+		t.Run(c.Expected, func(t *testing.T) {
+			// always reset the global IncludePath to the default for consistent test results
+			resolver.IncludePath = resolver.DefaultIncludePath
+
+			out := resolver.GetIncludePath(c.Args)
+			if out != c.Expected {
+				t.Errorf("expected %q, got %q", c.Expected, out)
+			}
+		})
+	}
+}
+
 func TestGithub(t *testing.T) {
 	resolver := resolver.NewGithubResolver()