Add beginnings of new cr command

go/src/infra/tools/cr/cmd/firstrun/firstrun_unix.go

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// +build !windows
+
+// *nix-specific function implementations for the firstrun subcommand.
+
+package firstrun
+
+import (
+        "os"
+        "os/user"
+        "path/filepath"
+
+        "infra/tools/cr/lib/terminal"
+)
+
+// firstrunCheckNotInstalled is a sanity check to make sure that the user really
+// wants to do firstrun again, if it looks like cr is already installed.
+func firstrunCheckNotInstalled() {
+        // Check to see if a path ending in '/cr/bin' in in $PATH.
+        pathenv := os.Getenv("PATH")
+        terminal.Debug("$PATH is %v\n", pathenv)
+        possibleDirs := make([]string, 1)
+        for _, elem := range filepath.SplitList(pathenv) {
+                terminal.Debug("Examining %v\n", elem)
+                head, bindir := filepath.Split(elem)
+                crdir := filepath.Base(head)
+                terminal.Debug("Last elements of path are %v, %v\n", crdir, bindir)
+                if bindir == "bin" && crdir == "cr" {
+                        possibleDirs = append(possibleDirs, elem)
+                }
+        }
+        terminal.Debug("Possible dirs are %v\n", possibleDirs)
+        // Check to see if an executable called 'cr' is in that path.

[seanmccullough1, 2016/05/06 00:43:54]

If this comment (and many others here) is a TODO, please mark it TODO.

[agable, 2016/05/10 00:34:10]

Done.

+}
+
+// firstrunPromptInstallDir prompts the user for a directory path to install cr.
+func firstrunPromptInstallDir() {
+        // Figure out a sane place to suggest.
+        _, err := user.Current()
+        if err != nil {

[seanmccullough1, 2016/05/06 00:43:54]

returning err here would fit naturally.

[agable, 2016/05/10 00:34:10]

Removed the stub, returns an error now.

+        }
+        // Suggest it and ask the user for an alternative.
+        // Check that the chosen directory makes sense.
+}
+
+// firstrunInitInstallDir sets up the selected directory to house cr. It creates
+// the modules/ and bin/ subdirectories, places the cr executable in the
+// top level, and symlinks it into bin/.
+func firstrunInitInstallDir(dir string) {
+        // Create the cr/ directory.
+        // Copy this executable into the cr/ directory.
+        // Create the bin/ subdirectory.
+        // Add a symlink to the cr executable in the bin/ subdirectory.
+        // Create the modules/ subdirectory.
+}
+
+// firstrunUpdatePath finds the rcfile in which $PATH is set, sees if it can
+// automatically update it, and prompts the user for permission to do so.
+func firstrunUpdatePath() {
+        // Detect the user's default shell.
+        // Find their shell's rcfile.
+        // Find lines modifying $PATH in that file.
+        // Fine a line mentioning depot_tools.
+        // Produce a git-style diff adding the install bin/ dir to that line, or
+        // above that line.
+        // Prompt the user to see if they want to apply that diff.
+        // Apply the diff, or print instructions on how to do it manually.
+}
+
+// firstrunPrintUpdatePathInstructions prints instructions for the user to
+// update their $PATH manually. This is used if updatePath fails, or if the user
+// declines to have their rcfile updated automatically.
+func firstrunPrintUpdatePathInstructions() {
+
+}