Implement dcmd package and use it to simplify cmd/dehub's implementation significantly

---
type: change
message: Implement dcmd package and use it to simplify cmd/dehub's implementation
  significantly
change_hash: AFNRl+3KopuAHWBIbfr9NzWuNMH+CV5kEMZt+1zEji3q
credentials:
- type: pgp_signature
  pub_key_id: 95C46FA6A41148AC
  body: 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
  account: mediocregopher

ROADMAP.md

@@ -26,7 +26,8 @@ set, only a sequence of milestones and the requirements to hit them.
 * Polish commands
     - New flag system, some kind of interactivity support (e.g. user doesn't
       specify required argument, give them a prompt on the CLI to input it
-      rather than an error. This can be built into the flag system.
+      rather than an error). This is partially done, in that a new flag system
+      has been started. Needs further work.
 
     - Review flags, probably make some of them into positional arguments,
       document everything better.

cmd/dehub/cmd_commit.go

@@ -0,0 +1,85 @@
+package main
+
+import (
+	"context"
+	"dehub"
+	"errors"
+	"fmt"
+
+	"dehub/cmd/dehub/dcmd"
+)
+
+func cmdCommit(ctx context.Context, cmd *dcmd.Cmd) {
+	flag := cmd.FlagSet()
+	msg := flag.String("msg", "", "Commit message")
+	accountID := flag.String("account-id", "", "Account to sign commit as")
+	cmd.Run(func() (context.Context, error) {
+		repo := ctxRepo(ctx)
+
+		// Don't bother checking any of the parameters, especially commit
+		// message, if there's no staged changes,
+		hasStaged, err := repo.HasStagedChanges()
+		if err != nil {
+			return nil, fmt.Errorf("error determining if any changes have been staged: %w", err)
+		} else if !hasStaged {
+			return nil, errors.New("no changes have been staged for commit")
+		}
+
+		if *accountID == "" {
+			return nil, errors.New("-account-id is required")
+		}
+
+		if *msg == "" {
+			var err error
+			if *msg, err = tmpFileMsg(); err != nil {
+				return nil, fmt.Errorf("error collecting commit message from user: %w", err)
+
+			} else if *msg == "" {
+				return nil, errors.New("empty commit message, not doing anything")
+			}
+		}
+
+		cfg, err := repo.LoadConfig()
+		if err != nil {
+			return nil, err
+		}
+
+		var account dehub.Account
+		var ok bool
+		for _, account = range cfg.Accounts {
+			if account.ID == *accountID {
+				ok = true
+				break
+			}
+		}
+		if !ok {
+			return nil, fmt.Errorf("account ID %q not found in config", *accountID)
+		} else if l := len(account.Signifiers); l == 0 || l > 1 {
+			return nil, fmt.Errorf("account %q has %d signifiers, only one is supported right now", *accountID, l)
+		}
+
+		sig := account.Signifiers[0]
+		sigInt, err := sig.Interface(*accountID)
+		if err != nil {
+			return nil, fmt.Errorf("could not cast %+v to SignifierInterface: %w", sig, err)
+		}
+
+		commit, err := repo.NewCommitChange(*msg)
+		if err != nil {
+			return nil, fmt.Errorf("could not construct change commit: %w", err)
+		}
+
+		commit, err = repo.AccreditCommit(commit, sigInt)
+		if err != nil {
+			return nil, fmt.Errorf("could not accredit commit: %w", err)
+		}
+
+		hash, err := repo.Commit(commit, *accountID)
+		if err != nil {
+			return nil, fmt.Errorf("could not commit change commit: %w", err)
+		}
+
+		fmt.Printf("changes committed to HEAD as %s\n", hash)
+		return nil, nil
+	})
+}

cmd/dehub/cmd_hook.go

@@ -0,0 +1,103 @@
+package main
+
+import (
+	"bufio"
+	"context"
+	"dehub/cmd/dehub/dcmd"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+func cmdHook(ctx context.Context, cmd *dcmd.Cmd) {
+	flag := cmd.FlagSet()
+	preRcv := flag.Bool("pre-receive", false, "Use dehub as a server-side pre-receive hook")
+
+	cmd.Run(func() (context.Context, error) {
+
+		if !*preRcv {
+			return nil, errors.New("must set the hook type")
+		}
+
+		repo := ctxRepo(ctx)
+
+		br := bufio.NewReader(os.Stdin)
+		for {
+			line, err := br.ReadString('\n')
+			if errors.Is(err, io.EOF) {
+				return nil, nil
+			} else if err != nil {
+				return nil, fmt.Errorf("error reading next line from stdin: %w", err)
+			}
+			fmt.Printf("Processing line %q\n", strings.TrimSpace(line))
+
+			lineParts := strings.Fields(line)
+			if len(lineParts) < 3 {
+				return nil, fmt.Errorf("malformed pre-receive hook stdin line %q", line)
+			}
+
+			branchName := plumbing.ReferenceName(lineParts[2])
+
+			// the zeroRevision gets sent on the very first push
+			const zeroRevision plumbing.Revision = "0000000000000000000000000000000000000000"
+
+			fromRev := plumbing.Revision(lineParts[0])
+			var fromHash *plumbing.Hash
+			if fromRev != zeroRevision {
+				fromHash, err = repo.GitRepo.ResolveRevision(fromRev)
+				if err != nil {
+					return nil, fmt.Errorf("unable to resolve revision %q: %w", fromRev, err)
+				}
+			}
+
+			toRev := plumbing.Revision(lineParts[1])
+			toHash, err := repo.GitRepo.ResolveRevision(toRev)
+			if err != nil {
+				return nil, fmt.Errorf("unable to resolve revision %q: %w", toRev, err)
+			}
+
+			toCommit, err := repo.GitRepo.CommitObject(*toHash)
+			if err != nil {
+				return nil, fmt.Errorf("unable to find commit %q: %w", *toHash, err)
+			}
+
+			var hashesToCheck []plumbing.Hash
+			var found bool
+			for currCommit := toCommit; ; {
+				hashesToCheck = append(hashesToCheck, currCommit.Hash)
+				if currCommit.NumParents() == 0 {
+					break
+				} else if currCommit.NumParents() > 1 {
+					return nil, fmt.Errorf("commit %q has more than one parent: %+v",
+						currCommit.Hash, currCommit.ParentHashes)
+				}
+
+				parentCommit, err := currCommit.Parent(0)
+				if err != nil {
+					return nil, fmt.Errorf("unable to get parent of commit %q: %w", currCommit.Hash, err)
+				} else if fromHash != nil && parentCommit.Hash == *fromHash {
+					found = true
+					break
+				}
+				currCommit = parentCommit
+			}
+			if !found && fromHash != nil {
+				return nil, fmt.Errorf("unable to find commit %q as an ancestor of %q", *fromHash, *toHash)
+			}
+
+			for i := len(hashesToCheck) - 1; i >= 0; i-- {
+				hash := hashesToCheck[i]
+				fmt.Printf("Verifying change commit %q\n", hash)
+				if err := repo.VerifyCommit(branchName, hash); err != nil {
+					return nil, fmt.Errorf("could not verify change commit %q: %w", hash, err)
+				}
+			}
+			fmt.Println("All pushed commits have been verified, well done.")
+			return nil, nil
+		}
+	})
+}

cmd/dehub/cmd_verify.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"context"
+	"dehub/cmd/dehub/dcmd"
+	"fmt"
+
+	"gopkg.in/src-d/go-git.v4/plumbing"
+)
+
+func cmdVerify(ctx context.Context, cmd *dcmd.Cmd) {
+	flag := cmd.FlagSet()
+	rev := flag.String("rev", "HEAD", "Revision of commit to verify")
+	branch := flag.String("branch", "", "Branch that the revision is on. If not given then the currently checked out branch is assumed")
+
+	cmd.Run(func() (context.Context, error) {
+		repo := ctxRepo(ctx)
+
+		h, err := repo.GitRepo.ResolveRevision(plumbing.Revision(*rev))
+		if err != nil {
+			return nil, fmt.Errorf("could not resolve revision %q: %w", *rev, err)
+		}
+
+		var branchName plumbing.ReferenceName
+		if *branch == "" {
+			if branchName, err = repo.CheckedOutBranch(); err != nil {
+				return nil, fmt.Errorf("could not determined currently checked out branch: %w", err)
+			}
+		} else {
+			branchName = plumbing.NewBranchReferenceName(*branch)
+		}
+
+		if err := repo.VerifyCommit(branchName, *h); err != nil {
+			return nil, fmt.Errorf("could not verify commit at %q (%s): %w", *rev, *h, err)
+		}
+
+		fmt.Printf("commit at %q (%s) is good to go!\n", *rev, *h)
+		return nil, nil
+	})
+}

cmd/dehub/dcmd/dcmd.go

@@ -0,0 +1,170 @@
+// Package dcmd implements command and sub-command parsing and runtime
+// management. It wraps the stdlib flag package as well, to incorporate
+// configuration into the mix.
+package dcmd
+
+import (
+	"context"
+	"errors"
+	"flag"
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+)
+
+func exitErr(err error) {
+	fmt.Fprintf(os.Stderr, "exiting: %v\n", err)
+	os.Stderr.Sync()
+	os.Stdout.Sync()
+	os.Exit(1)
+}
+
+type subCmd struct {
+	name, descr string
+	run         func(context.Context, *Cmd)
+}
+
+// Cmd wraps a flag.FlagSet instance to provide extra functionality that dehub
+// wants, specifically around sub-command support.
+type Cmd struct {
+	flagSet *flag.FlagSet
+	binary  string // only gets set on root Cmd, during Run
+	subCmds []subCmd
+
+	// these fields get set by the parent Cmd, if this is a sub-command.
+	name   string
+	args   []string
+	parent *Cmd
+}
+
+// New initializes and returns an empty Cmd instance.
+func New() *Cmd {
+	return &Cmd{}
+}
+
+func (cmd *Cmd) getFlagSet() *flag.FlagSet {
+	if cmd.flagSet == nil {
+		cmd.flagSet = flag.NewFlagSet(cmd.name, flag.ContinueOnError)
+	}
+	return cmd.flagSet
+}
+
+// FlagSet returns a flag.Cmd instance on which parameter creation methods can
+// be called, e.g. String(...) or Int(...).
+func (cmd *Cmd) FlagSet() *flag.FlagSet {
+	return cmd.getFlagSet()
+}
+
+// SubCmd registers a sub-command of this Cmd.
+//
+// A new Cmd will be instantiated when this sub-command is picked on the
+// command-line during this Cmd's Run method. The Context returned from that Run
+// and the new Cmd will be passed into the callback given here. The sub-command
+// should then be performed in the same manner as this Cmd is performed
+// (including setting flags, adding sub-sub-commands, etc...)
+func (cmd *Cmd) SubCmd(name, descr string, run func(context.Context, *Cmd)) {
+	cmd.subCmds = append(cmd.subCmds, subCmd{
+		name:  name,
+		descr: descr,
+		run:   run,
+	})
+
+	// it's not the most efficient to do this here, but it is the easiest
+	sort.Slice(cmd.subCmds, func(i, j int) bool {
+		return cmd.subCmds[i].name < cmd.subCmds[j].name
+	})
+}
+
+func (cmd *Cmd) printUsageHead(subCmdTitle string) {
+	var title string
+	if cmd.parent == nil {
+		title = fmt.Sprintf("USAGE: %s [flags]", cmd.binary)
+	} else {
+		title = fmt.Sprintf("%s [%s flags]", cmd.name, cmd.name)
+	}
+
+	if subCmdTitle != "" {
+		title += " " + subCmdTitle
+	} else if len(cmd.subCmds) > 0 {
+		title += fmt.Sprint(" <sub-command> [sub-command flags]")
+	}
+
+	if cmd.parent == nil {
+		fmt.Printf("\n%s\n\n", title)
+		fmt.Print("### FLAGS ###\n\n")
+	} else {
+		cmd.parent.printUsageHead(title)
+		fmt.Printf("### %s FLAGS ###\n\n", strings.ToUpper(cmd.name))
+	}
+
+	cmd.getFlagSet().PrintDefaults()
+	fmt.Print("\n")
+}
+
+// Run performs the comand. It starts by parsing all flags in the Cmd's FlagSet,
+// and possibly exiting with a usage message if appropriate. It will then
+// perform the given body callback, and then perform any sub-commands (if
+// selected).
+//
+// The context returned from the callback will be passed into the callback
+// (given to SubCmd) of any sub-commands which are run, and so on.
+func (cmd *Cmd) Run(body func() (context.Context, error)) {
+	args := cmd.args
+	if cmd.parent == nil {
+		cmd.binary, args = os.Args[0], os.Args[1:]
+	}
+
+	fs := cmd.getFlagSet()
+	fs.Usage = func() {
+		cmd.printUsageHead("")
+		if len(cmd.subCmds) == 0 {
+			return
+		}
+
+		fmt.Printf("### SUB-COMMANDS ###\n\n")
+		for _, subCmd := range cmd.subCmds {
+			fmt.Printf("\t%s : %s\n", subCmd.name, subCmd.descr)
+		}
+		fmt.Println("")
+	}
+
+	if err := fs.Parse(args); err != nil {
+		exitErr(err)
+		return
+	}
+
+	ctx, err := body()
+	if err != nil {
+		exitErr(err)
+	}
+
+	// body has run, now do sub-command (if there is one)
+	subArgs := fs.Args()
+	if len(cmd.subCmds) == 0 {
+		return
+	} else if len(subArgs) == 0 && len(cmd.subCmds) > 0 {
+		fs.Usage()
+		exitErr(errors.New("no sub-command selected"))
+	}
+
+	// now find that sub-command
+	subCmdName, args := strings.ToLower(args[0]), args[1:]
+	var subCmd subCmd
+	var subCmdOk bool
+	for _, subCmd = range cmd.subCmds {
+		if subCmdOk = subCmd.name == subCmdName; subCmdOk {
+			break
+		}
+	}
+	if !subCmdOk {
+		fs.Usage()
+		exitErr(fmt.Errorf("unknown command %q", subCmdName))
+	}
+
+	subCmdCmd := New()
+	subCmdCmd.name = subCmd.name
+	subCmdCmd.args = subArgs[1:]
+	subCmdCmd.parent = cmd
+	subCmd.run(ctx, subCmdCmd)
+}

cmd/dehub/main.go

@@ -1,375 +1,43 @@
 package main
 
 import (
-	"bufio"
+	"context"
-	"bytes"
 	"dehub"
-	"errors"
+	"dehub/cmd/dehub/dcmd"
-	"flag"
 	"fmt"
-	"io"
-	"io/ioutil"
 	"os"
-	"os/exec"
-	"strings"
-
-	"gopkg.in/src-d/go-git.v4/plumbing"
 )
 
-func exitErr(err error) {
+type cmdCtxKey int
-	fmt.Fprintf(os.Stderr, "exiting: %v\n", err)
-	os.Stderr.Sync()
-	os.Stdout.Sync()
-	os.Exit(1)
-}
 
-func tmpFileMsg() (string, error) {
+const (
-	editor := os.Getenv("EDITOR")
+	cmdCtxKeyRepo cmdCtxKey = iota
-	if editor == "" {
+)
-		return "", errors.New("EDITOR not set, please set it or use -msg in order to create your commit message")
-	} else if _, err := os.Stat(editor); err != nil {
-		return "", fmt.Errorf("could not stat EDITOR %q: %w", editor, err)
-	}
 
-	tmpf, err := ioutil.TempFile("", "")
+func ctxRepo(ctx context.Context) *dehub.Repo {
-	if err != nil {
+	repo, ok := ctx.Value(cmdCtxKeyRepo).(*dehub.Repo)
-		return "", fmt.Errorf("could not open temp file: %w", err)
-	}
-	tmpfName := tmpf.Name()
-	defer os.Remove(tmpfName)
-
-	tmpBody := bytes.NewBufferString(`
-
-# Please enter the commit message for your changes. Lines starting
-# with '#' will be ignored, and an empty message aborts the commit.`)
-
-	_, err = io.Copy(tmpf, tmpBody)
-	tmpf.Close()
-	if err != nil {
-		return "", fmt.Errorf("could not write helper message to temp file %q: %w", tmpfName, err)
-	}
-
-	cmd := exec.Command(editor, tmpfName)
-	cmd.Stdin = os.Stdin
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-	if err := cmd.Run(); err != nil {
-		return "", fmt.Errorf("error running '%s %q': %w", editor, tmpfName, err)
-	}
-
-	body, err := ioutil.ReadFile(tmpfName)
-	if err != nil {
-		return "", fmt.Errorf("error retrieving message body from %q: %w", tmpfName, err)
-	}
-
-	bodyFiltered := new(bytes.Buffer)
-	bodyBR := bufio.NewReader(bytes.NewBuffer(body))
-	for {
-		line, err := bodyBR.ReadString('\n')
-		if errors.Is(err, io.EOF) {
-			break
-		} else if err != nil {
-			return "", fmt.Errorf("error reading from buffered body: %w", err)
-		}
-
-		if !strings.HasPrefix(strings.TrimSpace(line), "#") {
-			bodyFiltered.WriteString(line)
-		}
-	}
-
-	return strings.TrimSpace(bodyFiltered.String()), nil
-}
-
-type subCmdCtx struct {
-	repo func() *dehub.Repo
-	flag *flag.FlagSet
-	args []string
-}
-
-func (sctx subCmdCtx) flagParse() {
-	if err := sctx.flag.Parse(sctx.args); err != nil {
-		exitErr(err)
-	}
-}
-
-type subCmd struct {
-	name, descr string
-	body        func(sctx subCmdCtx) error
-}
-
-var subCmds = []subCmd{
-	{
-		name:  "commit",
-		descr: "commits staged changes to the head of the current branch",
-		body: func(sctx subCmdCtx) error {
-			msg := sctx.flag.String("msg", "", "Commit message")
-			accountID := sctx.flag.String("account-id", "", "Account to sign commit as")
-			sctx.flagParse()
-
-			// Don't bother checking any of the parameters, especially commit
-			// message, if there's no staged changes,
-			hasStaged, err := sctx.repo().HasStagedChanges()
-			if err != nil {
-				return fmt.Errorf("error determining if any changes have been staged: %w", err)
-			} else if !hasStaged {
-				return errors.New("no changes have been staged for commit")
-			}
-
-			if *accountID == "" {
-				flag.PrintDefaults()
-				return errors.New("-account-id is required")
-			}
-
-			if *msg == "" {
-				var err error
-				if *msg, err = tmpFileMsg(); err != nil {
-					return fmt.Errorf("error collecting commit message from user: %w", err)
-
-				} else if *msg == "" {
-					return errors.New("empty commit message, not doing anything")
-				}
-			}
-
-			cfg, err := sctx.repo().LoadConfig()
-			if err != nil {
-				return err
-			}
-
-			var account dehub.Account
-			var ok bool
-			for _, account = range cfg.Accounts {
-				if account.ID == *accountID {
-					ok = true
-					break
-				}
-			}
 	if !ok {
-				return fmt.Errorf("account ID %q not found in config", *accountID)
+		panic("repo not initialized on the command context")
-			} else if l := len(account.Signifiers); l == 0 || l > 1 {
-				return fmt.Errorf("account %q has %d signifiers, only one is supported right now", *accountID, l)
 	}
-
+	return repo
-			sig := account.Signifiers[0]
-			sigInt, err := sig.Interface(*accountID)
-			if err != nil {
-				return fmt.Errorf("could not cast %+v to SignifierInterface: %w", sig, err)
-			}
-
-			commit, err := sctx.repo().NewCommitChange(*msg)
-			if err != nil {
-				return fmt.Errorf("could not construct change commit: %w", err)
-			}
-
-			commit, err = sctx.repo().AccreditCommit(commit, sigInt)
-			if err != nil {
-				return fmt.Errorf("could not accredit commit: %w", err)
-			}
-
-			hash, err := sctx.repo().Commit(commit, *accountID)
-			if err != nil {
-				return fmt.Errorf("could not commit change commit: %w", err)
-			}
-
-			fmt.Printf("changes committed to HEAD as %s\n", hash)
-			return nil
-		},
-	},
-	{
-		name:  "verify",
-		descr: "verifies one or more commits as having the proper credentials",
-		body: func(sctx subCmdCtx) error {
-			rev := sctx.flag.String("rev", "HEAD", "Revision of commit to verify")
-			branch := sctx.flag.String("branch", "", "Branch that the revision is on. If not given then the currently checked out branch is assumed")
-			sctx.flagParse()
-
-			h, err := sctx.repo().GitRepo.ResolveRevision(plumbing.Revision(*rev))
-			if err != nil {
-				return fmt.Errorf("could not resolve revision %q: %w", *rev, err)
-			}
-
-			var branchName plumbing.ReferenceName
-			if *branch == "" {
-				if branchName, err = sctx.repo().CheckedOutBranch(); err != nil {
-					return fmt.Errorf("could not determined currently checked out branch: %w", err)
-				}
-			} else {
-				branchName = plumbing.NewBranchReferenceName(*branch)
-			}
-
-			if err := sctx.repo().VerifyCommit(branchName, *h); err != nil {
-				return fmt.Errorf("could not verify commit at %q (%s): %w", *rev, *h, err)
-			}
-
-			fmt.Printf("commit at %q (%s) is good to go!\n", *rev, *h)
-			return nil
-		},
-	},
-	{
-		name:  "hook",
-		descr: "use dehub as a git hook",
-		body: func(sctx subCmdCtx) error {
-			preRcv := sctx.flag.Bool("pre-receive", false, "Use dehub as a server-side pre-receive hook")
-			sctx.flagParse()
-
-			if !*preRcv {
-				flag.PrintDefaults()
-				return errors.New("must set the hook type")
-			}
-
-			br := bufio.NewReader(os.Stdin)
-			for {
-				line, err := br.ReadString('\n')
-				if errors.Is(err, io.EOF) {
-					return nil
-				} else if err != nil {
-					return fmt.Errorf("error reading next line from stdin: %w", err)
-				}
-				fmt.Printf("Processing line %q\n", strings.TrimSpace(line))
-
-				lineParts := strings.Fields(line)
-				if len(lineParts) < 3 {
-					return fmt.Errorf("malformed pre-receive hook stdin line %q", line)
-				}
-
-				branchName := plumbing.ReferenceName(lineParts[2])
-
-				// the zeroRevision gets sent on the very first push
-				const zeroRevision plumbing.Revision = "0000000000000000000000000000000000000000"
-
-				fromRev := plumbing.Revision(lineParts[0])
-				var fromHash *plumbing.Hash
-				if fromRev != zeroRevision {
-					fromHash, err = sctx.repo().GitRepo.ResolveRevision(fromRev)
-					if err != nil {
-						return fmt.Errorf("unable to resolve revision %q: %w", fromRev, err)
-					}
-				}
-
-				toRev := plumbing.Revision(lineParts[1])
-				toHash, err := sctx.repo().GitRepo.ResolveRevision(toRev)
-				if err != nil {
-					return fmt.Errorf("unable to resolve revision %q: %w", toRev, err)
-				}
-
-				toCommit, err := sctx.repo().GitRepo.CommitObject(*toHash)
-				if err != nil {
-					return fmt.Errorf("unable to find commit %q: %w", *toHash, err)
-				}
-
-				var hashesToCheck []plumbing.Hash
-				var found bool
-				for currCommit := toCommit; ; {
-					hashesToCheck = append(hashesToCheck, currCommit.Hash)
-					if currCommit.NumParents() == 0 {
-						break
-					} else if currCommit.NumParents() > 1 {
-						return fmt.Errorf("commit %q has more than one parent: %+v",
-							currCommit.Hash, currCommit.ParentHashes)
-					}
-
-					parentCommit, err := currCommit.Parent(0)
-					if err != nil {
-						return fmt.Errorf("unable to get parent of commit %q: %w", currCommit.Hash, err)
-					} else if fromHash != nil && parentCommit.Hash == *fromHash {
-						found = true
-						break
-					}
-					currCommit = parentCommit
-				}
-				if !found && fromHash != nil {
-					return fmt.Errorf("unable to find commit %q as an ancestor of %q", *fromHash, *toHash)
-				}
-
-				for i := len(hashesToCheck) - 1; i >= 0; i-- {
-					hash := hashesToCheck[i]
-					fmt.Printf("Verifying change commit %q\n", hash)
-					if err := sctx.repo().VerifyCommit(branchName, hash); err != nil {
-						return fmt.Errorf("could not verify change commit %q: %w", hash, err)
-					}
-				}
-				fmt.Println("All pushed commits have been verified, well done.")
-				return nil
-			}
-		},
-	},
 }
 
 func main() {
-	var pickedSubCmd bool
+	cmd := dcmd.New()
-	var subCmd subCmd
+	flag := cmd.FlagSet()
-	flagSet := flag.NewFlagSet("dehub", flag.ContinueOnError)
+	bare := flag.Bool("bare", false, "If set then dehub will expect to be working with a bare repo")
-	flagSet.Usage = func() {
-		cmd := "<command>"
-		if pickedSubCmd {
-			cmd = subCmd.name
-		}
-		fmt.Printf("USAGE: %s [global flags] %s [command flags]\n\n", os.Args[0], cmd)
 
-		if !pickedSubCmd {
+	cmd.SubCmd("commit", "commits staged changes to the head of the current branch", cmdCommit)
-			fmt.Println("COMMANDS")
+	cmd.SubCmd("verify", "verifies one or more commits as having the proper credentials", cmdVerify)
-			for _, subCmd := range subCmds {
+	cmd.SubCmd("hook", "use dehub as a git hook", cmdHook)
-				fmt.Printf("\t%s : %s\n", subCmd.name, subCmd.descr)
-			}
-			fmt.Println("")
-		}
 
-		fmt.Println("GLOBAL FLAGS")
+	cmd.Run(func() (context.Context, error) {
-		flagSet.PrintDefaults()
+		repo, err := dehub.OpenRepo(".", dehub.OpenBare(*bare))
-		fmt.Println("")
-	}
-
-	bare := flagSet.Bool("bare", false, "If set then dehub will expect to be working with a bare repo")
-	if err := flagSet.Parse(os.Args[1:]); err != nil {
-		exitErr(err)
-		return
-	}
-
-	args := flagSet.Args()
-	if len(args) < 1 {
-		flagSet.Usage()
-		exitErr(errors.New("no command selected"))
-	}
-
-	subCmdName, args := strings.ToLower(args[0]), args[1:]
-	for _, subCmd = range subCmds {
-		if pickedSubCmd = subCmd.name == subCmdName; pickedSubCmd {
-			break
-		}
-	}
-
-	if !pickedSubCmd {
-		flagSet.Usage()
-		exitErr(fmt.Errorf("unknown command %q", subCmdName))
-	}
-
-	subFlagSet := flag.NewFlagSet(subCmd.name, flag.ExitOnError)
-	subFlagSet.Usage = func() {
-		flagSet.Usage()
-		fmt.Println("COMMAND FLAGS")
-		subFlagSet.PrintDefaults()
-		fmt.Println("")
-	}
-
-	var r *dehub.Repo
-	repoFn := func() *dehub.Repo {
-		if r != nil {
-			return r
-		}
-		var err error
-		if r, err = dehub.OpenRepo(".", dehub.OpenBare(*bare)); err != nil {
-			wd, _ := os.Getwd()
-			err = fmt.Errorf("failed to OpenRepo at %q: %w", wd, err)
-			exitErr(err)
-		}
-		return r
-	}
-
-	err := subCmd.body(subCmdCtx{
-		repo: repoFn,
-		flag: subFlagSet,
-		args: args,
-	})
 		if err != nil {
-		exitErr(err)
+			wd, _ := os.Getwd()
+			return nil, fmt.Errorf("failed to OpenRepo at %q: %w", wd, err)
 		}
+
+		return context.WithValue(context.Background(), cmdCtxKeyRepo, repo), nil
+	})
 }

cmd/dehub/tmp_file.go

@@ -0,0 +1,70 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+func tmpFileMsg() (string, error) {
+	editor := os.Getenv("EDITOR")
+	if editor == "" {
+		return "", errors.New("EDITOR not set, please set it or use -msg in order to create your commit message")
+	} else if _, err := os.Stat(editor); err != nil {
+		return "", fmt.Errorf("could not stat EDITOR %q: %w", editor, err)
+	}
+
+	tmpf, err := ioutil.TempFile("", "")
+	if err != nil {
+		return "", fmt.Errorf("could not open temp file: %w", err)
+	}
+	tmpfName := tmpf.Name()
+	defer os.Remove(tmpfName)
+
+	tmpBody := bytes.NewBufferString(`
+
+# Please enter the commit message for your changes. Lines starting
+# with '#' will be ignored, and an empty message aborts the commit.`)
+
+	_, err = io.Copy(tmpf, tmpBody)
+	tmpf.Close()
+	if err != nil {
+		return "", fmt.Errorf("could not write helper message to temp file %q: %w", tmpfName, err)
+	}
+
+	cmd := exec.Command(editor, tmpfName)
+	cmd.Stdin = os.Stdin
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		return "", fmt.Errorf("error running '%s %q': %w", editor, tmpfName, err)
+	}
+
+	body, err := ioutil.ReadFile(tmpfName)
+	if err != nil {
+		return "", fmt.Errorf("error retrieving message body from %q: %w", tmpfName, err)
+	}
+
+	bodyFiltered := new(bytes.Buffer)
+	bodyBR := bufio.NewReader(bytes.NewBuffer(body))
+	for {
+		line, err := bodyBR.ReadString('\n')
+		if errors.Is(err, io.EOF) {
+			break
+		} else if err != nil {
+			return "", fmt.Errorf("error reading from buffered body: %w", err)
+		}
+
+		if !strings.HasPrefix(strings.TrimSpace(line), "#") {
+			bodyFiltered.WriteString(line)
+		}
+	}
+
+	return strings.TrimSpace(bodyFiltered.String()), nil
+}