add support for git bisect

pkg/commands/git_commands/bisect.go

@@ -0,0 +1,164 @@
+package git_commands
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+type BisectCommands struct {
+	*GitCommon
+}
+
+func NewBisectCommands(gitCommon *GitCommon) *BisectCommands {
+	return &BisectCommands{
+		GitCommon: gitCommon,
+	}
+}
+
+// This command is pretty cheap to run so we're not storing the result anywhere.
+// But if it becomes problematic we can chang that.
+func (self *BisectCommands) GetInfo() *BisectInfo {
+	var err error
+	info := &BisectInfo{started: false, log: self.Log, newTerm: "bad", oldTerm: "good"}
+	// we return nil if we're not in a git bisect session.
+	// we know we're in a session by the presence of a .git/BISECT_START file
+
+	bisectStartPath := filepath.Join(self.dotGitDir, "BISECT_START")
+	exists, err := self.os.FileExists(bisectStartPath)
+	if err != nil {
+		self.Log.Infof("error getting git bisect info: %s", err.Error())
+		return info
+	}
+
+	if !exists {
+		return info
+	}
+
+	startContent, err := os.ReadFile(bisectStartPath)
+	if err != nil {
+		self.Log.Infof("error getting git bisect info: %s", err.Error())
+		return info
+	}
+
+	info.started = true
+	info.start = strings.TrimSpace(string(startContent))
+
+	termsContent, err := os.ReadFile(filepath.Join(self.dotGitDir, "BISECT_TERMS"))
+	if err != nil {
+		// old git versions won't have this file so we default to bad/good
+	} else {
+		splitContent := strings.Split(string(termsContent), "\n")
+		info.newTerm = splitContent[0]
+		info.oldTerm = splitContent[1]
+	}
+
+	bisectRefsDir := filepath.Join(self.dotGitDir, "refs", "bisect")
+	files, err := os.ReadDir(bisectRefsDir)
+	if err != nil {
+		self.Log.Infof("error getting git bisect info: %s", err.Error())
+		return info
+	}
+
+	info.statusMap = make(map[string]BisectStatus)
+	for _, file := range files {
+		status := BisectStatusSkipped
+		name := file.Name()
+		path := filepath.Join(bisectRefsDir, name)
+
+		fileContent, err := os.ReadFile(path)
+		if err != nil {
+			self.Log.Infof("error getting git bisect info: %s", err.Error())
+			return info
+		}
+
+		sha := strings.TrimSpace(string(fileContent))
+
+		if name == info.newTerm {
+			status = BisectStatusNew
+		} else if strings.HasPrefix(name, info.oldTerm+"-") {
+			status = BisectStatusOld
+		} else if strings.HasPrefix(name, "skipped-") {
+			status = BisectStatusSkipped
+		}
+
+		info.statusMap[sha] = status
+	}
+
+	currentContent, err := os.ReadFile(filepath.Join(self.dotGitDir, "BISECT_EXPECTED_REV"))
+	if err != nil {
+		self.Log.Infof("error getting git bisect info: %s", err.Error())
+		return info
+	}
+	currentSha := strings.TrimSpace(string(currentContent))
+	info.current = currentSha
+
+	return info
+}
+
+func (self *BisectCommands) Reset() error {
+	return self.cmd.New("git bisect reset").StreamOutput().Run()
+}
+
+func (self *BisectCommands) Mark(ref string, term string) error {
+	return self.cmd.New(
+		fmt.Sprintf("git bisect %s %s", term, ref),
+	).
+		IgnoreEmptyError().
+		StreamOutput().
+		Run()
+}
+
+func (self *BisectCommands) Skip(ref string) error {
+	return self.Mark(ref, "skip")
+}
+
+func (self *BisectCommands) Start() error {
+	return self.cmd.New("git bisect start").StreamOutput().Run()
+}
+
+// tells us whether we've found our problem commit(s). We return a string slice of
+// commit sha's if we're done, and that slice may have more that one item if
+// skipped commits are involved.
+func (self *BisectCommands) IsDone() (bool, []string, error) {
+	info := self.GetInfo()
+	if !info.Bisecting() {
+		return false, nil, nil
+	}
+
+	newSha := info.GetNewSha()
+	if newSha == "" {
+		return false, nil, nil
+	}
+
+	// if we start from the new commit and reach the a good commit without
+	// coming across any unprocessed commits, then we're done
+	done := false
+	candidates := []string{}
+
+	err := self.cmd.New(fmt.Sprintf("git rev-list %s", newSha)).RunAndProcessLines(func(line string) (bool, error) {
+		sha := strings.TrimSpace(line)
+
+		if status, ok := info.statusMap[sha]; ok {
+			switch status {
+			case BisectStatusSkipped, BisectStatusNew:
+				candidates = append(candidates, sha)
+				return false, nil
+			case BisectStatusOld:
+				done = true
+				return true, nil
+			}
+		} else {
+			return true, nil
+		}
+
+		// should never land here
+		return true, nil
+	})
+	if err != nil {
+		return false, nil, err
+	}
+
+	return done, candidates, nil
+}

pkg/commands/git_commands/bisect_info.go

@@ -0,0 +1,103 @@
+package git_commands
+
+import "github.com/sirupsen/logrus"
+
+// although the typical terms in a git bisect are 'bad' and 'good', they're more
+// generally known as 'new' and 'old'. Semi-recently git allowed the user to define
+// their own terms e.g. when you want to used 'fixed', 'unfixed' in the event
+// that you're looking for a commit that fixed a bug.
+
+// Git bisect only keeps track of a single 'bad' commit. Once you pick a commit
+// that's older than the current bad one, it forgets about the previous one. On
+// the other hand, it does keep track of all the good and skipped commits.
+
+type BisectInfo struct {
+	log *logrus.Entry
+
+	// tells us whether all our git bisect files are there meaning we're in bisect mode.
+	// Doesn't necessarily mean that we've actually picked a good/bad commit yet.
+	started bool
+
+	// this is the ref you started the commit from
+	start string // this will always be defined
+
+	// these will be defined if we've started
+	newTerm string // 'bad' by default
+	oldTerm string // 'good' by default
+
+	// map of commit sha's to their status
+	statusMap map[string]BisectStatus
+
+	// the sha of the commit that's under test
+	current string
+}
+
+type BisectStatus int
+
+const (
+	BisectStatusOld BisectStatus = iota
+	BisectStatusNew
+	BisectStatusSkipped
+)
+
+// null object pattern
+func NewNullBisectInfo() *BisectInfo {
+	return &BisectInfo{started: false}
+}
+
+func (self *BisectInfo) GetNewSha() string {
+	for sha, status := range self.statusMap {
+		if status == BisectStatusNew {
+			return sha
+		}
+	}
+
+	return ""
+}
+
+func (self *BisectInfo) GetCurrentSha() string {
+	return self.current
+}
+
+func (self *BisectInfo) StartSha() string {
+	return self.start
+}
+
+func (self *BisectInfo) Status(commitSha string) (BisectStatus, bool) {
+	status, ok := self.statusMap[commitSha]
+	return status, ok
+}
+
+func (self *BisectInfo) NewTerm() string {
+	return self.newTerm
+}
+
+func (self *BisectInfo) OldTerm() string {
+	return self.oldTerm
+}
+
+// this is for when we have called `git bisect start`. It does not
+// mean that we have actually started narrowing things down or selecting good/bad commits
+func (self *BisectInfo) Started() bool {
+	return self.started
+}
+
+// this is where we have both a good and bad revision and we're actually
+// starting to narrow things down
+func (self *BisectInfo) Bisecting() bool {
+	if !self.Started() {
+		return false
+	}
+
+	if self.GetNewSha() == "" {
+		return false
+	}
+
+	for _, status := range self.statusMap {
+		if status == BisectStatusOld {
+			return true
+		}
+	}
+
+	return false
+}

pkg/commands/git_commands/commit.go

@@ -75,7 +75,19 @@ func (self *CommitCommands) GetCommitMessage(commitSha string) (string, error) {
 }
 
 func (self *CommitCommands) GetCommitMessageFirstLine(sha string) (string, error) {
-	return self.cmd.New(fmt.Sprintf("git show --no-patch --pretty=format:%%s %s", sha)).DontLog().RunWithOutput()
+	return self.GetCommitMessagesFirstLine([]string{sha})
+}
+
+func (self *CommitCommands) GetCommitMessagesFirstLine(shas []string) (string, error) {
+	return self.cmd.New(
+		fmt.Sprintf("git show --no-patch --pretty=format:%%s %s", strings.Join(shas, " ")),
+	).DontLog().RunWithOutput()
+}
+
+func (self *CommitCommands) GetCommitsOneline(shas []string) (string, error) {
+	return self.cmd.New(
+		fmt.Sprintf("git show --no-patch --oneline %s", strings.Join(shas, " ")),
+	).DontLog().RunWithOutput()
 }
 
 // AmendHead amends HEAD with whatever is staged in your working tree