git-codereview/reword.go - review - Git at Google

 // Copyright 2020 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package main

 import (
 	"bytes"
 	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strings"
 )

 func cmdReword(args []string) {
 	flags.Usage = func() {
 		fmt.Fprintf(stderr(), "Usage: %s reword %s [commit...]\n",
 			progName, globalFlags)
 		exit(2)
 	}
 	flags.Parse(args)
 	args = flags.Args()

 	// Check that we understand the structure
 	// before we let the user spend time editing messages.
 	b := CurrentBranch()
 	pending := b.Pending()
 	if len(pending) == 0 {
 		dief("reword: no commits pending")
 	}
 	if b.Name == "HEAD" {
 		dief("reword: no current branch")
 	}
 	var last *Commit
 	for i := len(pending) - 1; i >= 0; i-- {
 		c := pending[i]
 		if last != nil && !c.HasParent(last.Hash) {
 			dief("internal error: confused about pending commit graph: parent %.7s vs %.7s", last.Hash, c.Parents)
 		}
 		last = c
 	}

 	headState := func() (head, branch string) {
 		head = trim(cmdOutput("git", "rev-parse", "HEAD"))
 		for _, line := range nonBlankLines(cmdOutput("git", "branch", "-l")) {
 			if strings.HasPrefix(line, "* ") {
 				branch = trim(line[1:])
 				return head, branch
 			}
 		}
 		dief("internal error: cannot find current branch")
 		panic("unreachable")
 	}

 	head, branch := headState()
 	if head != last.Hash {
 		dief("internal error: confused about pending commit graph: HEAD vs parent: %.7s vs %.7s", head, last.Hash)
 	}
 	if branch != b.Name {
 		dief("internal error: confused about pending commit graph: branch name %s vs %s", branch, b.Name)
 	}

 	// Build list of commits to be reworded.
 	// Do first, in case there are typos on the command line.
 	var cs []*Commit
 	newMsg := make(map[*Commit]string)
 	if len(args) == 0 {
 		for _, c := range pending {
 			cs = append(cs, c)
 		}
 	} else {
 		for _, arg := range args {
 			c := b.CommitByRev("reword", arg)
 			cs = append(cs, c)
 		}
 	}
 	for _, c := range cs {
 		newMsg[c] = ""
 	}

 	// Invoke editor to reword all the messages message.
 	// Save the edits to REWORD_MSGS immediately after editor exit
 	// in case we for some reason cannot apply the changes - don't want
 	// to throw away the user's writing.
 	// But we don't use REWORD_MSGS as the actual editor file,
 	// because if there are multiple git rewords happening
 	// (perhaps the user has forgotten about one in another window),
 	// we don't want them to step on each other during editing.
 	var buf bytes.Buffer
 	saveFile := filepath.Join(gitPathDir(), "REWORD_MSGS")
 	saveBuf := func() {
 		if err := ioutil.WriteFile(saveFile, buf.Bytes(), 0666); err != nil {
 			dief("cannot save messages: %v", err)
 		}
 	}
 	saveBuf() // make sure it works before we let the user edit anything
 	printf("editing messages (new texts logged in %s in case of failure)", saveFile)
 	note := "edited messages saved in " + saveFile

 	if len(cs) == 1 {
 		c := cs[0]
 		edited := editor(c.Message)
 		if edited == "" {
 			dief("edited message is empty")
 		}
 		newMsg[c] = edited
 		fmt.Fprintf(&buf, "# %s\n\n%s\n\n", c.Subject, edited)
 		saveBuf()
 	} else {
 		// Edit all at once.
 		var ed bytes.Buffer
 		ed.WriteString(rewordProlog)
 		byHash := make(map[string]*Commit)
 		for _, c := range cs {
 			if strings.HasPrefix(c.Message, "# ") || strings.Contains(c.Message, "\n# ") {
 				// Will break our framing.
 				// Should be pretty rare since 'git commit' and 'git commit --amend'
 				// delete lines beginning with # after editing sessions.
 				dief("commit %.7s has a message line beginning with # - cannot reword with other commits", c.Hash)
 			}
 			hash := c.Hash[:7]
 			byHash[hash] = c
 			// Two blank lines before #, one after.
 			// Lots of space to make it easier to see the boundaries
 			// between commit messages.
 			fmt.Fprintf(&ed, "\n\n# %s %s\n\n%s\n", hash, c.Subject, c.Message)
 		}
 		edited := editor(ed.String())
 		if edited == "" {
 			dief("edited text is empty")
 		}

 		// Save buffer for user before going further.
 		buf.WriteString(edited)
 		saveBuf()

 		for i, text := range strings.Split("\n"+edited, "\n# ") {
 			if i == 0 {
 				continue
 			}
 			text = "# " + text // restore split separator

 			// Pull out # hash header line and body.
 			hdr, body, _ := cut(text, "\n")

 			// Cut blank lines at start and end of body but keep newline-terminated.
 			for body != "" {
 				line, rest, _ := cut(body, "\n")
 				if line != "" {
 					break
 				}
 				body = rest
 			}
 			body = strings.TrimRight(body, " \t\n")
 			if body != "" {
 				body += "\n"
 			}

 			// Look up hash.
 			f := strings.Fields(hdr)
 			if len(f) < 2 {
 				dief("edited text has # line with no commit hash\n%s", note)
 			}
 			c := byHash[f[1]]
 			if c == nil {
 				dief("cannot find commit for header: %s\n%s", strings.TrimSpace(hdr), note)
 			}
 			newMsg[c] = body
 		}
 	}

 	// Rebuild the commits the way git would,
 	// but without doing any git checkout that
 	// would affect the files in the working directory.
 	var newHash string
 	last = nil
 	for i := len(pending) - 1; i >= 0; i-- {
 		c := pending[i]
 		if (newMsg[c] == "" || newMsg[c] == c.Message) && newHash == "" {
 			// Have not started making changes yet. Leave exactly as is.
 			last = c
 			continue
 		}
 		// Rebuilding.
 		msg := newMsg[c]
 		if msg == "" {
 			msg = c.Message
 		}
 		if last != nil && newHash != "" && !c.HasParent(last.Hash) {
 			dief("internal error: confused about pending commit graph")
 		}
 		gitArgs := []string{"commit-tree", "-p"}
 		for _, p := range c.Parents {
 			if last != nil && newHash != "" && p == last.Hash {
 				p = newHash
 			}
 			gitArgs = append(gitArgs, p)
 		}
 		gitArgs = append(gitArgs, "-m", msg, c.Tree)
 		os.Setenv("GIT_AUTHOR_NAME", c.AuthorName)
 		os.Setenv("GIT_AUTHOR_EMAIL", c.AuthorEmail)
 		os.Setenv("GIT_AUTHOR_DATE", c.AuthorDate)
 		newHash = trim(cmdOutput("git", gitArgs...))
 		last = c
 	}
 	if newHash == "" {
 		// No messages changed.
 		return
 	}

 	// Attempt swap of HEAD but leave index and working copy alone.
 	// No obvious way to make it atomic, but check for races.
 	head, branch = headState()
 	if head != pending[0].Hash {
 		dief("cannot reword: commits changed underfoot\n%s", note)
 	}
 	if branch != b.Name {
 		dief("cannot reword: branch changed underfoot\n%s", note)
 	}
 	run("git", "reset", "--soft", newHash)
 }

 func cut(s, sep string) (before, after string, ok bool) {
 	i := strings.Index(s, sep)
 	if i < 0 {
 		return s, "", false
 	}
 	return s[:i], s[i+len(sep):], true
 }

 var rewordProlog = `Rewording multiple commit messages.
 The # lines separate the different commits and must be left unchanged.
 `
	// Copyright 2020 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package main

	import (
	"bytes"
	"fmt"
	"io/ioutil"
	"os"
	"path/filepath"
	"strings"
	)

	func cmdReword(args []string) {
	flags.Usage = func() {
	fmt.Fprintf(stderr(), "Usage: %s reword %s [commit...]\n",
	progName, globalFlags)
	exit(2)
	}
	flags.Parse(args)
	args = flags.Args()

	// Check that we understand the structure
	// before we let the user spend time editing messages.
	b := CurrentBranch()
	pending := b.Pending()
	if len(pending) == 0 {
	dief("reword: no commits pending")
	}
	if b.Name == "HEAD" {
	dief("reword: no current branch")
	}
	var last *Commit
	for i := len(pending) - 1; i >= 0; i-- {
	c := pending[i]
	if last != nil && !c.HasParent(last.Hash) {
	dief("internal error: confused about pending commit graph: parent %.7s vs %.7s", last.Hash, c.Parents)
	}
	last = c
	}

	headState := func() (head, branch string) {
	head = trim(cmdOutput("git", "rev-parse", "HEAD"))
	for _, line := range nonBlankLines(cmdOutput("git", "branch", "-l")) {
	if strings.HasPrefix(line, "* ") {
	branch = trim(line[1:])
	return head, branch
	}
	}
	dief("internal error: cannot find current branch")
	panic("unreachable")
	}

	head, branch := headState()
	if head != last.Hash {
	dief("internal error: confused about pending commit graph: HEAD vs parent: %.7s vs %.7s", head, last.Hash)
	}
	if branch != b.Name {
	dief("internal error: confused about pending commit graph: branch name %s vs %s", branch, b.Name)
	}

	// Build list of commits to be reworded.
	// Do first, in case there are typos on the command line.
	var cs []*Commit
	newMsg := make(map[*Commit]string)
	if len(args) == 0 {
	for _, c := range pending {
	cs = append(cs, c)
	}
	} else {
	for _, arg := range args {
	c := b.CommitByRev("reword", arg)
	cs = append(cs, c)
	}
	}
	for _, c := range cs {
	newMsg[c] = ""
	}

	// Invoke editor to reword all the messages message.
	// Save the edits to REWORD_MSGS immediately after editor exit
	// in case we for some reason cannot apply the changes - don't want
	// to throw away the user's writing.
	// But we don't use REWORD_MSGS as the actual editor file,
	// because if there are multiple git rewords happening
	// (perhaps the user has forgotten about one in another window),
	// we don't want them to step on each other during editing.
	var buf bytes.Buffer
	saveFile := filepath.Join(gitPathDir(), "REWORD_MSGS")
	saveBuf := func() {
	if err := ioutil.WriteFile(saveFile, buf.Bytes(), 0666); err != nil {
	dief("cannot save messages: %v", err)
	}
	}
	saveBuf() // make sure it works before we let the user edit anything
	printf("editing messages (new texts logged in %s in case of failure)", saveFile)
	note := "edited messages saved in " + saveFile

	if len(cs) == 1 {
	c := cs[0]
	edited := editor(c.Message)
	if edited == "" {
	dief("edited message is empty")
	}
	newMsg[c] = edited
	fmt.Fprintf(&buf, "# %s\n\n%s\n\n", c.Subject, edited)
	saveBuf()
	} else {
	// Edit all at once.
	var ed bytes.Buffer
	ed.WriteString(rewordProlog)
	byHash := make(map[string]*Commit)
	for _, c := range cs {
	if strings.HasPrefix(c.Message, "# ") \|\| strings.Contains(c.Message, "\n# ") {
	// Will break our framing.
	// Should be pretty rare since 'git commit' and 'git commit --amend'
	// delete lines beginning with # after editing sessions.
	dief("commit %.7s has a message line beginning with # - cannot reword with other commits", c.Hash)
	}
	hash := c.Hash[:7]
	byHash[hash] = c
	// Two blank lines before #, one after.
	// Lots of space to make it easier to see the boundaries
	// between commit messages.
	fmt.Fprintf(&ed, "\n\n# %s %s\n\n%s\n", hash, c.Subject, c.Message)
	}
	edited := editor(ed.String())
	if edited == "" {
	dief("edited text is empty")
	}

	// Save buffer for user before going further.
	buf.WriteString(edited)
	saveBuf()

	for i, text := range strings.Split("\n"+edited, "\n# ") {
	if i == 0 {
	continue
	}
	text = "# " + text // restore split separator

	// Pull out # hash header line and body.
	hdr, body, _ := cut(text, "\n")

	// Cut blank lines at start and end of body but keep newline-terminated.
	for body != "" {
	line, rest, _ := cut(body, "\n")
	if line != "" {
	break
	}
	body = rest
	}
	body = strings.TrimRight(body, " \t\n")
	if body != "" {
	body += "\n"
	}

	// Look up hash.
	f := strings.Fields(hdr)
	if len(f) < 2 {
	dief("edited text has # line with no commit hash\n%s", note)
	}
	c := byHash[f[1]]
	if c == nil {
	dief("cannot find commit for header: %s\n%s", strings.TrimSpace(hdr), note)
	}
	newMsg[c] = body
	}
	}

	// Rebuild the commits the way git would,
	// but without doing any git checkout that
	// would affect the files in the working directory.
	var newHash string
	last = nil
	for i := len(pending) - 1; i >= 0; i-- {
	c := pending[i]
	if (newMsg[c] == "" \|\| newMsg[c] == c.Message) && newHash == "" {
	// Have not started making changes yet. Leave exactly as is.
	last = c
	continue
	}
	// Rebuilding.
	msg := newMsg[c]
	if msg == "" {
	msg = c.Message
	}
	if last != nil && newHash != "" && !c.HasParent(last.Hash) {
	dief("internal error: confused about pending commit graph")
	}
	gitArgs := []string{"commit-tree", "-p"}
	for _, p := range c.Parents {
	if last != nil && newHash != "" && p == last.Hash {
	p = newHash
	}
	gitArgs = append(gitArgs, p)
	}
	gitArgs = append(gitArgs, "-m", msg, c.Tree)
	os.Setenv("GIT_AUTHOR_NAME", c.AuthorName)
	os.Setenv("GIT_AUTHOR_EMAIL", c.AuthorEmail)
	os.Setenv("GIT_AUTHOR_DATE", c.AuthorDate)
	newHash = trim(cmdOutput("git", gitArgs...))
	last = c
	}
	if newHash == "" {
	// No messages changed.
	return
	}

	// Attempt swap of HEAD but leave index and working copy alone.
	// No obvious way to make it atomic, but check for races.
	head, branch = headState()
	if head != pending[0].Hash {
	dief("cannot reword: commits changed underfoot\n%s", note)
	}
	if branch != b.Name {
	dief("cannot reword: branch changed underfoot\n%s", note)
	}
	run("git", "reset", "--soft", newHash)
	}

	func cut(s, sep string) (before, after string, ok bool) {
	i := strings.Index(s, sep)
	if i < 0 {
	return s, "", false
	}
	return s[:i], s[i+len(sep):], true
	}

	var rewordProlog = `Rewording multiple commit messages.
	The # lines separate the different commits and must be left unchanged.
	`