Add -gopath flag to init

- Separate network mode and GOPATH mode of operations.
- In GOPATH mode, fetch projectData by searching through the current
GOPATH. Solve the dependency constraints based on the projects found on
disk and use network to solve for projects not found on disk.
- In Network mode, do not check GOPATH or any ondisk projects. Solve the
dependency constraints completely over network.

cmd/dep/init.go

@@ -46,10 +46,12 @@ func (cmd *initCommand) Hidden() bool      { return false }
 
 func (cmd *initCommand) Register(fs *flag.FlagSet) {
 	fs.BoolVar(&cmd.noExamples, "no-examples", false, "don't include example in Gopkg.toml")
+	fs.BoolVar(&cmd.gopath, "gopath", false, "search in GOPATH for dependencies")
 }
 
 type initCommand struct {
 	noExamples bool
+	gopath     bool
 }
 
 func trimPathPrefix(p1, p2 string) string {
@@ -112,39 +114,50 @@ func (cmd *initCommand) Run(ctx *dep.Ctx, args []string) error {
 	sm.UseDefaultSignalHandling()
 	defer sm.Release()
 
-	pd, err := getProjectData(ctx, pkgT, cpr, sm)
-	if err != nil {
-		return err
-	}
+	// Create empty manifest, lock and projectData, and fill them according to
+	// init operation modes. If gopath flag is set, fetch projectData by searching
+	// through GOPATH, else operate in network mode, solve all the dependencies
+	// over network.
 	m := &dep.Manifest{
-		Dependencies: pd.constraints,
+		Dependencies: make(gps.ProjectConstraints),
 	}
+	l := &dep.Lock{}
+	var pd projectData
 
-	// Make an initial lock from what knowledge we've collected about the
-	// versions on disk
-	l := &dep.Lock{
-		P: make([]gps.LockedProject, 0, len(pd.ondisk)),
-	}
+	if cmd.gopath {
+		pd, err = getProjectData(ctx, pkgT, cpr, sm)
+		if err != nil {
+			return err
+		}
 
-	for pr, v := range pd.ondisk {
-		// That we have to chop off these path prefixes is a symptom of
-		// a problem in gps itself
-		pkgs := make([]string, 0, len(pd.dependencies[pr]))
-		prslash := string(pr) + "/"
-		for _, pkg := range pd.dependencies[pr] {
-			if pkg == string(pr) {
-				pkgs = append(pkgs, ".")
-			} else {
-				pkgs = append(pkgs, trimPathPrefix(pkg, prslash))
-			}
+		m.Dependencies = pd.constraints
+
+		// Make an initial lock from what knowledge we've collected about the
+		// versions on disk
+		l = &dep.Lock{
+			P: make([]gps.LockedProject, 0, len(pd.ondisk)),
 		}
 
-		l.P = append(l.P, gps.NewLockedProject(
-			gps.ProjectIdentifier{ProjectRoot: pr}, v, pkgs),
-		)
+		for pr, v := range pd.ondisk {
+			// That we have to chop off these path prefixes is a symptom of
+			// a problem in gps itself
+			pkgs := make([]string, 0, len(pd.dependencies[pr]))
+			prslash := string(pr) + "/"
+			for _, pkg := range pd.dependencies[pr] {
+				if pkg == string(pr) {
+					pkgs = append(pkgs, ".")
+				} else {
+					pkgs = append(pkgs, trimPathPrefix(pkg, prslash))
+				}
+			}
+
+			l.P = append(l.P, gps.NewLockedProject(
+				gps.ProjectIdentifier{ProjectRoot: pr}, v, pkgs),
+			)
+		}
 	}
 
-	// Run solver with project versions found on disk
+	// Run solver with the available knowledge to solve the dependency constraints
 	internal.Vlogf("Solving...")
 	params := gps.SolveParameters{
 		RootDir:         root,
@@ -170,14 +183,22 @@ func (cmd *initCommand) Run(ctx *dep.Ctx, args []string) error {
 	}
 	l = dep.LockFromInterface(soln)
 
-	// Pick notondisk project constraints from solution and add to manifest
-	for k, _ := range pd.notondisk {
-		for _, x := range l.Projects() {
-			if k == x.Ident().ProjectRoot {
-				m.Dependencies[k] = getProjectPropertiesFromVersion(x.Version())
-				break
+	// Populate manifest based on operation mode.
+	if cmd.gopath {
+		// Pick notondisk project constraints from solution and add to manifest
+		for k, _ := range pd.notondisk {
+			for _, x := range l.Projects() {
+				if k == x.Ident().ProjectRoot {
+					m.Dependencies[k] = getProjectPropertiesFromVersion(x.Version())
+					break
+				}
 			}
 		}
+	} else {
+		// Pick all the solved projects from the above solution and add to manifest
+		for _, x := range l.Projects() {
+			m.Dependencies[x.Ident().ProjectRoot] = getProjectPropertiesFromVersion(x.Version())
+		}
 	}
 
 	// Run gps.Prepare with appropriate constraint solutions from solve run