Bold questions

internal/git/git.go

@@ -1,9 +1,12 @@
 package git
 
 import (
+	"errors"
 	"fmt"
+	"os"
 	"os/exec"
 	"path/filepath"
+	"strconv"
 	"strings"
 )
 
@@ -75,12 +78,194 @@ func RemoveWorktree(repo, path, branch string) error {
 	return err
 }
 
+type Unmerged struct {
+	Commits     int
+	Files       int
+	Insertions  int
+	Deletions   int
+	Uncommitted int
+}
+
+type ConflictError struct {
+	Files []string
+}
+
+func (e *ConflictError) Error() string {
+	return "merge conflicts in " + strings.Join(e.Files, ", ")
+}
+
+func UnmergedChanges(worktree, target string) (Unmerged, error) {
+	u := Unmerged{}
+
+	count, err := run(worktree, "rev-list", "--count", target+"..HEAD")
+	if err != nil {
+		return u, err
+	}
+	u.Commits, err = strconv.Atoi(count)
+	if err != nil {
+		return u, err
+	}
+
+	status, err := run(worktree, "status", "--porcelain", "--untracked-files=all")
+	if err != nil {
+		return u, err
+	}
+	if status != "" {
+		u.Uncommitted = len(strings.Split(status, "\n"))
+	}
+
+	tree, err := Snapshot(worktree)
+	if err != nil {
+		return u, err
+	}
+	base, err := run(worktree, "merge-base", target, "HEAD")
+	if err != nil {
+		return u, err
+	}
+	numstat, err := run(worktree, "diff", "--numstat", base, tree)
+	if err != nil {
+		return u, err
+	}
+	for _, line := range strings.Split(numstat, "\n") {
+		if line == "" {
+			continue
+		}
+		fields := strings.SplitN(line, "\t", 3)
+		u.Files++
+		adds, err := strconv.Atoi(fields[0])
+		if err != nil {
+			continue
+		}
+		dels, err := strconv.Atoi(fields[1])
+		if err != nil {
+			continue
+		}
+		u.Insertions += adds
+		u.Deletions += dels
+	}
+
+	return u, nil
+}
+
+func SquashMerge(repo, worktree, target, message string, env []string) (string, error) {
+	checkedOut, err := run(repo, "symbolic-ref", "--short", "HEAD")
+	if err != nil {
+		return "", err
+	}
+	if checkedOut != target {
+		return "", fmt.Errorf("%s has %s checked out, not %s", repo, checkedOut, target)
+	}
+
+	tree, err := Snapshot(worktree)
+	if err != nil {
+		return "", err
+	}
+	base, err := run(worktree, "merge-base", target, "HEAD")
+	if err != nil {
+		return "", err
+	}
+	head, err := run(repo, "rev-parse", target)
+	if err != nil {
+		return "", err
+	}
+
+	out, stderr, code, err := runCode(repo, nil, "merge-tree", "--write-tree", "--name-only", "--merge-base="+base, head, tree)
+	if err != nil {
+		return "", err
+	}
+	lines := strings.Split(out, "\n")
+	if code == 1 {
+		conflict := &ConflictError{}
+		for _, l := range lines[1:] {
+			if l == "" {
+				break
+			}
+			conflict.Files = append(conflict.Files, l)
+		}
+		return "", conflict
+	}
+	if code != 0 {
+		return "", fmt.Errorf("git merge-tree exited %d: %s", code, stderr)
+	}
+
+	headTree, err := run(repo, "rev-parse", head+"^{tree}")
+	if err != nil {
+		return "", err
+	}
+	if lines[0] == headTree {
+		return "", nil
+	}
+
+	commit, err := runEnv(repo, env, "commit-tree", lines[0], "-p", head, "-m", message)
+	if err != nil {
+		return "", err
+	}
+
+	_, err = run(repo, "merge", "--ff-only", commit)
+	if err != nil {
+		return "", err
+	}
+	return commit, nil
+}
+
+func Head(dir string) (string, error) {
+	return run(dir, "rev-parse", "HEAD")
+}
+
+func CommitAll(dir, message, name, email string) (string, error) {
+	status, err := run(dir, "status", "--porcelain", "--untracked-files=all")
+	if err != nil {
+		return "", err
+	}
+	if status == "" {
+		return "", nil
+	}
+
+	env := []string{
+		"GIT_AUTHOR_NAME=" + name,
+		"GIT_AUTHOR_EMAIL=" + email,
+		"GIT_COMMITTER_NAME=" + name,
+		"GIT_COMMITTER_EMAIL=" + email,
+	}
+	_, err = runEnv(dir, env, "add", "--all")
+	if err != nil {
+		return "", err
+	}
+	_, err = runEnv(dir, env, "commit", "--quiet", "--message", message)
+	if err != nil {
+		return "", err
+	}
+	return Head(dir)
+}
+
 func run(dir string, args ...string) (string, error) {
+	return runEnv(dir, nil, args...)
+}
+
+func runEnv(dir string, env []string, args ...string) (string, error) {
+	out, stderr, code, err := runCode(dir, env, args...)
+	if err != nil {
+		return "", err
+	}
+	if code != 0 {
+		return "", fmt.Errorf("git %s: exit status %d: %s", strings.Join(args, " "), code, stderr)
+	}
+	return out, nil
+}
+
+func runCode(dir string, env []string, args ...string) (string, string, int, error) {
 	cmd := exec.Command("git", args...)
 	cmd.Dir = dir
-	out, err := cmd.CombinedOutput()
-	if err != nil {
-		return "", fmt.Errorf("git %s: %w: %s", strings.Join(args, " "), err, strings.TrimSpace(string(out)))
+	cmd.Env = append(os.Environ(), env...)
+	stderr := &strings.Builder{}
+	cmd.Stderr = stderr
+	out, err := cmd.Output()
+	exit := &exec.ExitError{}
+	if errors.As(err, &exit) {
+		return strings.TrimSpace(string(out)), strings.TrimSpace(stderr.String()), exit.ExitCode(), nil
 	}
-	return strings.TrimSpace(string(out)), nil
+	if err != nil {
+		return "", "", 0, fmt.Errorf("git %s: %w", strings.Join(args, " "), err)
+	}
+	return strings.TrimSpace(string(out)), strings.TrimSpace(stderr.String()), 0, nil
 }