From e4c1cc3e7765d25c4f7cedd0544405872ba37241 Mon Sep 17 00:00:00 2001
From: Rene Zbinden <rene.zbinden@postfinance.ch>
Date: Mon, 6 Mar 2017 22:25:50 +0100
Subject: [PATCH 1/3] add help task

Signed-off-by: Andrey Nering <andrey.nering@gmail.com>
---
 README.md | 31 +++++++++++++++++++++++++++++++
 task.go   | 29 +++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/README.md b/README.md
index db63cf6a..dce10a8f 100644
--- a/README.md
+++ b/README.md
@@ -268,6 +268,37 @@ printos:
     - echo 'Is SH? {{IsSH}}'
 ```
 
+### Help
+
+Running `task help` lists all tasks with a description. The following taskfile:
+
+```yml
+build:
+  desc: Build the go binary.
+  cmds:
+    - go build -v -i main.go
+
+test:
+  desc: Run all the go tests.
+  cmds:
+    - go test -race ./...
+
+js:
+  cmds:
+    - npm run buildjs
+
+css:
+  cmds:
+    - npm run buildcss
+```
+
+would print the following output:
+
+```bash
+build   Build the go binary.
+test    Run all the go tests.
+```
+
 ## Alternatives
 
 Similar software:
diff --git a/task.go b/task.go
index f0df8923..74282988 100644
--- a/task.go
+++ b/task.go
@@ -4,8 +4,10 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"sort"
 	"strings"
 	"sync"
+	"text/tabwriter"
 
 	"github.com/go-task/task/execext"
 
@@ -30,6 +32,7 @@ var (
 type Task struct {
 	Cmds      []string
 	Deps      []string
+	Desc      string
 	Sources   []string
 	Generates []string
 	Dir       string
@@ -73,6 +76,11 @@ func RunTask(name string) error {
 
 	t, ok := Tasks[name]
 	if !ok {
+		tasks := tasksWithDesc()
+		if len(tasks) > 0 {
+			help(tasks)
+			return nil
+		}
 		return &taskNotFoundError{name}
 	}
 
@@ -202,3 +210,24 @@ func (t *Task) runCommand(i int) error {
 	}
 	return nil
 }
+
+func help(tasks []string) {
+	w := new(tabwriter.Writer)
+	// Format in tab-separated columns with a tab stop of 8.
+	w.Init(os.Stdout, 0, 8, 0, '\t', 0)
+	for _, task := range tasks {
+		fmt.Fprintln(w, fmt.Sprintf("%s\t%s", task, Tasks[task].Desc))
+	}
+	w.Flush()
+}
+
+func tasksWithDesc() []string {
+	tasks := []string{}
+	for name, task := range Tasks {
+		if len(task.Desc) > 0 {
+			tasks = append(tasks, name)
+		}
+	}
+	sort.Strings(tasks)
+	return tasks
+}

From 2054a1bc34dd17af9e237af84b11311bfe0df7f3 Mon Sep 17 00:00:00 2001
From: Andrey Nering <andrey.nering@gmail.com>
Date: Sun, 19 Mar 2017 15:18:18 -0300
Subject: [PATCH 2/3] Minor improvements for tasks description

---
 help.go | 33 +++++++++++++++++++++++++++++++++
 task.go | 38 ++++++++++----------------------------
 2 files changed, 43 insertions(+), 28 deletions(-)
 create mode 100644 help.go

diff --git a/help.go b/help.go
new file mode 100644
index 00000000..3f085dbc
--- /dev/null
+++ b/help.go
@@ -0,0 +1,33 @@
+package task
+
+import (
+	"fmt"
+	"os"
+	"sort"
+	"text/tabwriter"
+)
+
+func printExistingTasksHelp() {
+	tasks := tasksWithDesc()
+	if len(tasks) == 0 {
+		return
+	}
+	fmt.Println("Available tasks for this project:")
+
+	// Format in tab-separated columns with a tab stop of 8.
+	w := tabwriter.NewWriter(os.Stdout, 0, 8, 0, '\t', 0)
+	for _, task := range tasks {
+		fmt.Fprintln(w, fmt.Sprintf("- %s:\t%s", task, Tasks[task].Desc))
+	}
+	w.Flush()
+}
+
+func tasksWithDesc() (tasks []string) {
+	for name, task := range Tasks {
+		if task.Desc != "" {
+			tasks = append(tasks, name)
+		}
+	}
+	sort.Strings(tasks)
+	return
+}
diff --git a/task.go b/task.go
index 74282988..984a5531 100644
--- a/task.go
+++ b/task.go
@@ -4,10 +4,8 @@ import (
 	"fmt"
 	"log"
 	"os"
-	"sort"
 	"strings"
 	"sync"
-	"text/tabwriter"
 
 	"github.com/go-task/task/execext"
 
@@ -57,6 +55,16 @@ func Run() {
 		log.Fatal(err)
 	}
 
+	// check if given tasks exist
+	for _, a := range args {
+		if _, ok := Tasks[a]; !ok {
+			var err error = &taskNotFoundError{taskName: a}
+			fmt.Println(err)
+			printExistingTasksHelp()
+			return
+		}
+	}
+
 	for _, a := range args {
 		if err = RunTask(a); err != nil {
 			log.Fatal(err)
@@ -76,11 +84,6 @@ func RunTask(name string) error {
 
 	t, ok := Tasks[name]
 	if !ok {
-		tasks := tasksWithDesc()
-		if len(tasks) > 0 {
-			help(tasks)
-			return nil
-		}
 		return &taskNotFoundError{name}
 	}
 
@@ -210,24 +213,3 @@ func (t *Task) runCommand(i int) error {
 	}
 	return nil
 }
-
-func help(tasks []string) {
-	w := new(tabwriter.Writer)
-	// Format in tab-separated columns with a tab stop of 8.
-	w.Init(os.Stdout, 0, 8, 0, '\t', 0)
-	for _, task := range tasks {
-		fmt.Fprintln(w, fmt.Sprintf("%s\t%s", task, Tasks[task].Desc))
-	}
-	w.Flush()
-}
-
-func tasksWithDesc() []string {
-	tasks := []string{}
-	for name, task := range Tasks {
-		if len(task.Desc) > 0 {
-			tasks = append(tasks, name)
-		}
-	}
-	sort.Strings(tasks)
-	return tasks
-}

From 1cabfc636fca6bac1ceb41fd6c2a4c5551579044 Mon Sep 17 00:00:00 2001
From: Andrey Nering <andrey.nering@gmail.com>
Date: Sun, 19 Mar 2017 15:18:59 -0300
Subject: [PATCH 3/3] Add descs to Taskfile

---
 Taskfile.yml | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Taskfile.yml b/Taskfile.yml
index 70c45244..816f138a 100644
--- a/Taskfile.yml
+++ b/Taskfile.yml
@@ -1,20 +1,24 @@
 # compiles current source code and make "task" executable available on
 # $GOPATH/bin/task{.exe}
 install:
+  desc: Installs Task
   cmds:
     - go install -v ./...
 
 lint:
+  desc: Runs golint
   cmds:
     - golint .
     - golint ./cmd/task
 
 test:
+  desc: Runs test suite
   deps: [install]
   cmds:
     - go test -v
 
 # https://github.com/goreleaser/goreleaser
 release:
+  desc: Release Task
   cmds:
     - goreleaser