Use man content for `help <cmd>' and '<cmd> --help'

Call 'go generate ./commands' to create string entries from .ronns which
the cobra command can then use (added to the build scripts)

.gitignore

@@ -23,3 +23,4 @@ repos
 docker/*.key
 
 src
+commands/mancontent_gen.go

commands/commands.go

@@ -16,6 +16,9 @@ import (
 	"github.com/github/git-lfs/vendor/_nuts/github.com/spf13/cobra"
 )
 
+// Populate man pages
+//go:generate go run ../docs/man/mangen.go
+
 var (
 	Debugging    = false
 	ErrorBuffer  = &bytes.Buffer{}
@@ -29,6 +32,7 @@ var (
 			cmd.Usage()
 		},
 	}
+	ManPages = make(map[string]string, 20)
 )
 
 // Error prints a formatted message to Stderr.  It also gets printed to the
@@ -218,6 +222,28 @@ func determineIncludeExcludePaths(includeArg, excludeArg string) (include, exclu
 	return includePaths, excludePaths
 }
 
+// help is used for 'git-lfs help <command>'
+func help(cmd *cobra.Command, args []string) {
+	if txt, ok := ManPages[cmd.Use]; ok {
+		fmt.Fprintf(os.Stderr, txt)
+	} else {
+		fmt.Fprintf(os.Stderr, "Sorry, no help text found\n")
+	}
+}
+
+// usage is used for 'git-lfs <command> --help' or wen invoked manually
+func usage(cmd *cobra.Command) error {
+	if txt, ok := ManPages[cmd.Use]; ok {
+		fmt.Fprintf(os.Stderr, txt)
+	} else {
+		fmt.Fprintf(os.Stderr, "Sorry, no usage text found\n")
+	}
+	return nil
+}
+
 func init() {
 	log.SetOutput(ErrorWriter)
+	// Set up help/usage funcs based on manpage text
+	RootCmd.SetHelpFunc(help)
+	RootCmd.SetUsageFunc(usage)
 }

docs/man/mangen.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+// Reads all .ronn files & and converts them to string literals
+// triggered by "go generate" comment
+// Literals are inserted into a map using an init function, this means
+// that there are no compilation errors if 'go generate' hasn't been run, just
+// blank man files.
+func main() {
+	fmt.Fprintf(os.Stderr, "Converting man pages into code...\n")
+	mandir := "../docs/man"
+	fs, err := ioutil.ReadDir(mandir)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to open man dir: %v\n", err)
+		os.Exit(2)
+	}
+	out, err := os.Create("../commands/mancontent_gen.go")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to create go file: %v\n", err)
+		os.Exit(2)
+	}
+	out.WriteString("package commands\n\nfunc init() {\n")
+	out.WriteString("// THIS FILE IS GENERATED, DO NOT EDIT\n")
+	out.WriteString("// Use 'go generate ./commands' to update\n")
+	r := regexp.MustCompile(`git-lfs(?:-([A-Za-z\-]+))?.\d.ronn`)
+	count := 0
+	for _, f := range fs {
+		if match := r.FindStringSubmatch(f.Name()); match != nil {
+			fmt.Fprintf(os.Stderr, "%v\n", f.Name())
+			cmd := match[1]
+			if len(cmd) == 0 {
+				// This is git-lfs.1.ronn
+				cmd = "git-lfs"
+			}
+			out.WriteString("ManPages[\"" + cmd + "\"] = `")
+			contentf, err := os.Open(filepath.Join(mandir, f.Name()))
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "Failed to open %v: %v\n", f.Name(), err)
+				os.Exit(2)
+			}
+			// Process the ronn to make it nicer as help text
+			scanner := bufio.NewScanner(contentf)
+			for scanner.Scan() {
+				line := strings.TrimSpace(scanner.Text())
+				// Remove backticks since it won't format & that's delimiting the string
+				line = strings.Replace(line, "`", "", -1)
+				// Maybe more e.g. ## ?
+				out.WriteString(line + "\n")
+			}
+			out.WriteString("`\n")
+			contentf.Close()
+			count++
+		}
+	}
+	out.WriteString("}\n")
+	fmt.Fprintf(os.Stderr, "Successfully processed %d man pages.\n", count)
+
+}

script/build.go

@@ -38,6 +38,11 @@ func mainBuild() {
 
 	fmt.Printf("Using %s\n", runtime.Version())
 
+	genOut, err := exec.Command("go", "generate", "./commands").CombinedOutput()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "go generate failed:\n%v", genOut)
+		os.Exit(1)
+	}
 	cmd, _ := exec.Command("git", "rev-parse", "--short", "HEAD").Output()
 
 	if len(cmd) > 0 {