git sync: dry-run flag (git-town#1015)

features/git-town-sync/current_branch/feature_branch/no_conflict/dry_run.feature

@@ -0,0 +1,40 @@
+Feature: git-town sync: syncing the current feature branch with a tracking branch with dry run
+
+  As a developer wanting to test out syncing a feature branch
+  I want a dry run flag that doesn't run any commands
+  So that I can be confident in what the tool does before I use it
+
+
+  Background:
+    Given I have a feature branch named "feature"
+    And the following commits exist in my repository
+      | BRANCH  | LOCATION | MESSAGE               | FILE NAME           |
+      | main    | local    | local main commit     | local_main_file     |
+      |         | remote   | remote main commit    | remote_main_file    |
+      | feature | local    | local feature commit  | local_feature_file  |
+      |         | remote   | remote feature commit | remote_feature_file |
+    And I am on the "feature" branch
+    And I have an uncommitted file
+    When I run `git-town sync --dry-run`
+
+
+  Scenario: result
+    Then it runs the commands
+      | BRANCH  | COMMAND                            |
+      | feature | git fetch --prune                  |
+      |         | git add -A                         |
+      |         | git stash                          |
+      |         | git checkout main                  |
+      | main    | git rebase origin/main             |
+      |         | git push                           |
+      |         | git checkout feature               |
+      | feature | git merge --no-edit origin/feature |
+      |         | git merge --no-edit main           |
+      |         | git push                           |
+      |         | git stash pop                      |
+    And I am still on the "feature" branch
+    And I still have my uncommitted file
+    And I have the following commits
+      | BRANCH  | LOCATION | MESSAGE              | FILE NAME          |
+      | main    | local    | local main commit    | local_main_file    |
+      | feature | local    | local feature commit | local_feature_file |

src/cmd/shared.go

@@ -10,13 +10,15 @@ var (
 	abortFlag,
 	allFlag,
 	continueFlag,
+	dryRunFlag,
 	skipFlag,
 	undoFlag bool
 )
 
 var abortFlagDescription = "Abort a previous command that resulted in a conflict"
 var continueFlagDescription = "Continue a previous command that resulted in a conflict"
 var undoFlagDescription = "Undo a previous command"
+var dryRunFlagDescription = "Output the commands that would be run without them"
 
 func validateArgsCount(args []string, count int) error {
 	err := validateMinArgs(args, count)

src/cmd/sync.go

@@ -63,6 +63,9 @@ the main branch is synced with its upstream counterpart.`,
 		if err != nil {
 			return err
 		}
+		if dryRunFlag {
+			script.ActivateDryRun()
+		}
 		prompt.EnsureIsConfigured()
 		return nil
 	},
@@ -104,6 +107,7 @@ func init() {
 	syncCmd.Flags().BoolVar(&allFlag, "all", false, "Sync all local branches")
 	syncCmd.Flags().BoolVar(&abortFlag, "abort", false, abortFlagDescription)
 	syncCmd.Flags().BoolVar(&continueFlag, "continue", false, continueFlagDescription)
+	syncCmd.Flags().BoolVar(&dryRunFlag, "dry-run", false, dryRunFlagDescription)
 	syncCmd.Flags().BoolVar(&skipFlag, "skip", false, "Continue a previous command by skipping the branch that resulted in a conflicted")
 	RootCmd.AddCommand(syncCmd)
 }

src/dryrun/index.go

@@ -0,0 +1,25 @@
+package dryrun
+
+var currentBranchName = ""
+var isActive = false
+
+// Activate enables dry-run mode
+func Activate(initialBranchName string) {
+	isActive = true
+	SetCurrentBranchName(initialBranchName)
+}
+
+// IsActive returns whether of not dry-run mode is active
+func IsActive() bool {
+	return isActive
+}
+
+// GetCurrentBranchName returns the current branch name for dry-run mode
+func GetCurrentBranchName() string {
+	return currentBranchName
+}
+
+// SetCurrentBranchName sets the current branch name for dry-run mode
+func SetCurrentBranchName(branchName string) {
+	currentBranchName = branchName
+}

src/git/branch.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"strings"
 
+	"github.com/Originate/git-town/src/dryrun"
 	"github.com/Originate/git-town/src/exit"
 	"github.com/Originate/git-town/src/util"
 )
@@ -47,6 +48,9 @@ func EnsureIsPerennialBranch(branchName, errorMessage string) {
 
 // GetCurrentBranchName returns the name of the currently checked out branch
 func GetCurrentBranchName() string {
+	if dryrun.IsActive() {
+		return dryrun.GetCurrentBranchName()
+	}
 	if IsRebaseInProgress() {
 		return getCurrentBranchNameDuringRebase()
 	}

src/script/script.go

@@ -7,13 +7,27 @@ import (
 	"runtime"
 	"strings"
 
+	"github.com/Originate/git-town/src/dryrun"
 	"github.com/Originate/git-town/src/exit"
 	"github.com/Originate/git-town/src/git"
 	"github.com/Originate/git-town/src/util"
 
 	"github.com/fatih/color"
 )
 
+var dryRunMessage = `
+In dry run mode. No commands will be run. When run in normal mode, the command
+output will appear beneath the command. Some commands will only be run if
+necessary. For example: 'git push' will run if and only if there are local
+commits not on the remote.
+`
+
+// ActivateDryRun causes all commands to not be run
+func ActivateDryRun() {
+	color.New(color.FgBlue).Print(dryRunMessage)
+	dryrun.Activate(git.GetCurrentBranchName())
+}
+
 // OpenBrowser opens the default browser with the given URL.
 func OpenBrowser(url string) {
 	command := util.GetOpenBrowserCommand()
@@ -43,6 +57,12 @@ func PrintCommand(cmd ...string) {
 // RunCommand executes the given command-line operation.
 func RunCommand(cmd ...string) error {
 	PrintCommand(cmd...)
+	if dryrun.IsActive() {
+		if len(cmd) == 3 && cmd[0] == "git" && cmd[1] == "checkout" {
+			dryrun.SetCurrentBranchName(cmd[2])
+		}
+		return nil
+	}
 	// Windows commands run inside CMD
 	// because opening browsers is done via "start"
 	if runtime.GOOS == "windows" {

src/steps/push_branch_step.go

@@ -1,6 +1,7 @@
 package steps
 
 import (
+	"github.com/Originate/git-town/src/dryrun"
 	"github.com/Originate/git-town/src/git"
 	"github.com/Originate/git-town/src/script"
 )
@@ -24,7 +25,7 @@ func (step *PushBranchStep) CreateUndoStepBeforeRun() Step {
 
 // Run executes this step.
 func (step *PushBranchStep) Run() error {
-	if !git.ShouldBranchBePushed(step.BranchName) {
+	if !git.ShouldBranchBePushed(step.BranchName) && !dryrun.IsActive() {
 		return nil
 	}
 	if step.Force {