Strip out an directory-based replacements from main pkg's module (#78)

Per much previous discussion, we do apply replace directives in the main
package's module. But for directory replacements this is not guaranteed
to make sense. Indeed it almost certainly doesn't make sense most of the
time. Therefore, strip out these replace directives, leaving behind the
versioned, non-directory replaces.

main.go

@@ -474,6 +474,19 @@ type listPkg struct {
 	}
 }
 
+type modEditModule struct {
+	Path    string
+	Version string
+}
+
+type modEdit struct {
+	Module  modEditModule
+	Replace []struct {
+		Old modEditModule
+		New modEditModule
+	}
+}
+
 // arg is a wrapper around a command line-provided package
 type arg struct {
 	patt     string     // the command line-provided pattern
@@ -610,6 +623,43 @@ func (a *arg) list(proxy string) error {
 				return err
 			}
 
+			// now we need to drop all the replacements for which the RHS value does
+			// not include a version... because these are directory replacements
+			{
+				var out bytes.Buffer
+				gmeCmd := goCommand("mod", "edit", "-json")
+				gmeCmd.Dir = a.wd
+				gmeCmd.Stdout = &out
+				gmeCmd.Env = buildEnv("")
+				if err := gmeCmd.run(); err != nil {
+					return err
+				}
+				var mod modEdit
+				if err := json.Unmarshal(out.Bytes(), &mod); err != nil {
+					return fmt.Errorf("failed to process output of %v: %v\n%s", strings.Join(gmeCmd.Args, " "), err, out.Bytes())
+				}
+				var todrop []string
+				for _, r := range mod.Replace {
+					if r.New.Version != "" {
+						continue
+					}
+					drop := r.Old.Path
+					if r.Old.Version != "" {
+						drop += "@" + r.Old.Version
+					}
+					todrop = append(todrop, "-dropreplace="+drop)
+				}
+				if len(todrop) > 0 {
+					gmeCmd := goCommand("mod", "edit")
+					gmeCmd.Args = append(gmeCmd.Args, todrop...)
+					gmeCmd.Dir = a.wd
+					gmeCmd.Env = buildEnv("")
+					if err := gmeCmd.run(); err != nil {
+						return err
+					}
+				}
+			}
+
 			// now that we effectively have a copy of everything relevant in the
 			// target module (including replace directives), list to ensure they
 			// have been resolved

testdata/mod/github.com_gobin-testrepos_simple-main-directory-replace_v1.0.0.txt

@@ -0,0 +1,27 @@
+-- .mod --
+module github.com/gobin-testrepos/simple-main-directory-replace
+
+require github.com/gobin-testrepos/food v1.0.0
+
+replace github.com/gobin-testrepos/food => /road/to/nowhere
+-- .info --
+{"Version":"v1.0.0","Time":"2018-10-22T18:45:39Z"}
+
+-- go.mod --
+module github.com/gobin-testrepos/simple-main-directory-replace
+
+require github.com/gobin-testrepos/food v1.0.0
+
+replace github.com/gobin-testrepos/food => /road/to/nowhere
+
+-- main.go --
+package main
+
+import "fmt"
+
+import "github.com/gobin-testrepos/food"
+
+func main() {
+	fmt.Println("Simple module-based main v1.0.0")
+	fmt.Printf("Today we will eat %v\n", food.MainCourse)
+}

testdata/replace_directory.txt

@@ -0,0 +1,7 @@
+# Verify that directory-target replace statements in the main package's module
+# are ignored.
+
+env HOME=$WORK/home
+gobin -run github.com/gobin-testrepos/simple-main-directory-replace@v1.0.0
+stdout '^Simple module-based main v1.0.0$'
+stdout '^Today we will eat fish$'