feat: git retime 支持重排提交日期，新增 install.sh

- 新增 --start-date：按原顺序从指定日期起重排提交日期，默认每天一个
- 新增 --per-day 控制每天提交数、--day-gap 控制日期间隔；两者需配合
  --start-date 使用，否则报错提示
- 不给 --start-date 时保持原行为（保留原日期，只改时分秒）
- 预览在重排模式下显示完整的新日期时间，并说明日期规则
- install.sh：补 shebang 与可执行权限，构建后安装到 /usr/local/bin
- 文档：README.git.md 增加「重排日期」小节与选项表

internal/executor/executor.go

@@ -116,10 +116,10 @@ func (p Plan) Run(ctx context.Context, opts Options) error {
 			return fmt.Errorf("未注册的内置动作 %q", variant.Builtin)
 		}
 		return fn(ctx, BuiltinRequest{
-			Args:   p.ExtraArgs,
-			Stdin:  opts.Stdin,
-			Stdout: opts.Stdout,
-			Stderr: opts.Stderr,
+			Args:      p.ExtraArgs,
+			Stdin:     opts.Stdin,
+			Stdout:    opts.Stdout,
+			Stderr:    opts.Stderr,
 			Info:      p.Result.Info,
 			Plan:      p,
 			Confirmed: opts.Confirmed,

internal/executor/gitretime.go

@@ -32,6 +32,13 @@ type retimeOptions struct {
 	// spacing found on the remote branch. A zero (or out-of-range) entry falls
 	// back to a random gap.
 	Gaps []time.Duration
+
+	// StartDate, when set, re-dates the commits instead of keeping their
+	// original days: the selected commits are laid out in order starting at
+	// StartDate, stepping DayGap days per day and PerDay commits per day.
+	StartDate time.Time
+	DayGap    int // days between consecutive commit days, at least 1
+	PerDay    int // commits placed on one day, 0 means "unlimited" (one day only)
 }
 
 // defaultRetimeOptions matches the command's documented behaviour: commits land
@@ -59,33 +66,60 @@ func planRetime(commits []gitCommit, opts retimeOptions) []retime {
 	window := opts.WindowEnd - opts.WindowStart
 	out := make([]retime, 0, len(commits))
 
+	// When a start date is given, days are assigned rather than inherited.
+	redate := !opts.StartDate.IsZero()
+	if redate && opts.DayGap < 1 {
+		opts.DayGap = 1
+	}
+
 	// Group by calendar day, preserving order.
 	var dayCommits []gitCommit
-	currentDay := time.Time{}
+	var day time.Time
 	flush := func() {
 		if len(dayCommits) == 0 {
 			return
 		}
-		out = append(out, planDay(dayCommits, opts, window)...)
+		out = append(out, planDay(day, dayCommits, opts, window)...)
 		dayCommits = nil
 	}
 
 	for _, c := range commits {
-		day := c.Date()
-		if !currentDay.IsZero() && !day.Equal(currentDay) {
+		if redate {
+			// Start a new day whenever the current one is full.
+			if len(dayCommits) == 0 {
+				if !day.IsZero() {
+					day = day.AddDate(0, 0, opts.DayGap)
+				} else {
+					day = midnightOf(opts.StartDate)
+				}
+			}
+			if opts.PerDay > 0 && len(dayCommits) >= opts.PerDay {
+				flush()
+				day = day.AddDate(0, 0, opts.DayGap)
+			}
+			dayCommits = append(dayCommits, c)
+			continue
+		}
+
+		original := c.Date()
+		if !day.IsZero() && !original.Equal(day) {
 			flush()
 		}
-		currentDay = day
+		day = original
 		dayCommits = append(dayCommits, c)
 	}
 	flush()
 	return out
 }
 
+// midnightOf returns the start of the calendar day of t, in t's location.
+func midnightOf(t time.Time) time.Time {
+	return time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location())
+}
+
 // planDay spreads one day's commits across the window.
-func planDay(commits []gitCommit, opts retimeOptions, window time.Duration) []retime {
+func planDay(day time.Time, commits []gitCommit, opts retimeOptions, window time.Duration) []retime {
 	out := make([]retime, 0, len(commits))
-	day := commits[0].Date()
 
 	offsets, squeezed := spreadWithin(day, len(commits), opts, window)
 

internal/executor/gitretime_cmd.go

@@ -25,6 +25,12 @@ type gitRetimeOptions struct {
 	Branch     string
 	NoPush     bool
 	MatchEmote bool // --interval match-remote
+
+	// Redating: when StartDate is set, the selected commits are re-dated in
+	// order starting there instead of keeping their original days.
+	StartDate time.Time
+	DayGap    int
+	PerDay    int
 }
 
 // runGitRetime rewrites the timestamps of commits in [From, To] so they land
@@ -110,8 +116,18 @@ func writeRetimePreview(req BuiltinRequest, plan retimePlan, opts gitRetimeOptio
 	fmt.Fprintf(w, "改写:   %d 个提交（分支 %s，远程 %s）\n", len(plan.Commits), plan.Branch, plan.Remote)
 	fmt.Fprintf(w, "强推:   %s\n", pushSummary(plan, opts))
 	fmt.Fprintf(w, "目标:   %s\n", target)
-	fmt.Fprintf(w, "窗口:   %s-%s（保留原日期）\n\n",
-		clockOf(opts.Window), clockOf(opts.WindowEnd))
+	dateRule := "保留原日期"
+	if !opts.StartDate.IsZero() {
+		dateRule = "从 " + opts.StartDate.Format("2006-01-02") + " 起重排"
+		if opts.PerDay > 0 {
+			dateRule += fmt.Sprintf("，每天 %d 个", opts.PerDay)
+		}
+		if opts.DayGap > 1 {
+			dateRule += fmt.Sprintf("，间隔 %d 天", opts.DayGap)
+		}
+	}
+	fmt.Fprintf(w, "窗口:   %s-%s（%s）\n\n",
+		clockOf(opts.Window), clockOf(opts.WindowEnd), dateRule)
 
 	rows := [][]string{{"提交", "原时间", "新时间", "主题"}}
 	for _, item := range plan.Commits {
@@ -122,13 +138,21 @@ func writeRetimePreview(req BuiltinRequest, plan retimePlan, opts gitRetimeOptio
 		rows = append(rows, []string{
 			item.Short,
 			item.OldAuthor.Format("2006-01-02 15:04:05"),
-			item.NewTime.Format("15:04:05") + mark,
+			newTimeCell(item, opts) + mark,
 			item.Subject,
 		})
 	}
 	writeDisplayColumns(w, rows)
 }
 
+// newTimeCell shows the new time, with its date when dates are reassigned.
+func newTimeCell(item retime, opts gitRetimeOptions) string {
+	if opts.StartDate.IsZero() {
+		return item.NewTime.Format("15:04:05")
+	}
+	return item.NewTime.Format("2006-01-02 15:04:05")
+}
+
 // pushSummary states whether the branch will be force pushed.
 func pushSummary(plan retimePlan, opts gitRetimeOptions) string {
 	if opts.NoPush {
@@ -193,6 +217,9 @@ func collectRetimePlan(ctx context.Context, runner gitRunner, opts gitRetimeOpti
 		MaxGap:      opts.MaxGap,
 		FirstGapMax: 20 * time.Minute,
 		Rand:        newRetimeRand(opts.Seed),
+		StartDate:   opts.StartDate,
+		DayGap:      opts.DayGap,
+		PerDay:      opts.PerDay,
 	}
 	_ = opts.MatchEmote
 	return buildPlan(selected, plannerOpts, branch, remote), nil
@@ -353,6 +380,34 @@ func parseGitRetimeArgs(args []string, now time.Time) (gitRetimeOptions, bool, e
 			opts.Branch = v
 		case "--no-push":
 			opts.NoPush = true
+		case "--start-date":
+			v, err := takeValue()
+			if err != nil {
+				return opts, false, err
+			}
+			if opts.StartDate, err = parseDate(v); err != nil {
+				return opts, false, err
+			}
+		case "--day-gap":
+			v, err := takeValue()
+			if err != nil {
+				return opts, false, err
+			}
+			n, err := strconv.Atoi(v)
+			if err != nil || n < 1 {
+				return opts, false, fmt.Errorf("--day-gap 需要大于 0 的整数（天数），收到 %q", v)
+			}
+			opts.DayGap = n
+		case "--per-day":
+			v, err := takeValue()
+			if err != nil {
+				return opts, false, err
+			}
+			n, err := strconv.Atoi(v)
+			if err != nil || n < 1 {
+				return opts, false, fmt.Errorf("--per-day 需要大于 0 的整数（每天提交数），收到 %q", v)
+			}
+			opts.PerDay = n
 		default:
 			return opts, false, fmt.Errorf("未知选项 %q", arg)
 		}
@@ -382,6 +437,17 @@ func parseGitRetimeArgs(args []string, now time.Time) (gitRetimeOptions, bool, e
 	if opts.MaxGap <= opts.MinGap {
 		return opts, false, fmt.Errorf("间隔上限必须大于下限")
 	}
+	// --day-gap / --per-day only make sense together with --start-date.
+	if opts.StartDate.IsZero() {
+		if opts.DayGap > 0 || opts.PerDay > 0 {
+			return opts, false, fmt.Errorf("--day-gap 与 --per-day 需要配合 --start-date 使用" +
+				"（不给 --start-date 时保留每个提交的原日期）")
+		}
+		opts.DayGap = 1
+	} else if opts.DayGap < 1 {
+		// Re-dating defaults to consecutive days.
+		opts.DayGap = 1
+	}
 	return opts, confirmed, nil
 }
 

internal/executor/gitretime_cmd_test.go

@@ -423,3 +423,47 @@ func fixtureResp(args ...string) gitResponse {
 	}
 	return r
 }
+
+func TestParseGitRetimeArgsRedate(t *testing.T) {
+	opts, _, err := parseGitRetimeArgs([]string{
+		"2026-10-01", "2026-10-15",
+		"--start-date", "2026-11-01",
+		"--per-day", "2",
+		"--day-gap", "3",
+	}, time.Now())
+	if err != nil {
+		t.Fatalf("parse: %v", err)
+	}
+	if opts.StartDate.Format("2006-01-02") != "2026-11-01" || opts.PerDay != 2 || opts.DayGap != 3 {
+		t.Fatalf("opts = %+v", opts)
+	}
+}
+
+func TestParseGitRetimeArgsRedateValidation(t *testing.T) {
+	tests := []struct {
+		args []string
+		want string
+	}{
+		{[]string{"2026-10-01", "2026-10-02", "--per-day", "2"}, "需要配合 --start-date"},
+		{[]string{"2026-10-01", "2026-10-02", "--day-gap", "2"}, "需要配合 --start-date"},
+		{[]string{"2026-10-01", "2026-10-02", "--start-date", "2026/11/01"}, "YYYY-MM-DD"},
+		{[]string{"2026-10-01", "2026-10-02", "--start-date", "2026-11-01", "--per-day", "0"}, "大于 0"},
+		{[]string{"2026-10-01", "2026-10-02", "--start-date", "2026-11-01", "--day-gap", "x"}, "大于 0"},
+	}
+	for _, tc := range tests {
+		_, _, err := parseGitRetimeArgs(tc.args, time.Now())
+		if err == nil || !strings.Contains(err.Error(), tc.want) {
+			t.Errorf("args %v: err = %v, want %q", tc.args, err, tc.want)
+		}
+	}
+}
+
+func TestParseGitRetimeArgsDefaultDayGap(t *testing.T) {
+	opts, _, err := parseGitRetimeArgs([]string{"2026-10-01", "2026-10-02", "--start-date", "2026-11-01"}, time.Now())
+	if err != nil {
+		t.Fatalf("parse: %v", err)
+	}
+	if opts.DayGap != 1 {
+		t.Errorf("DayGap = %d, want the default 1", opts.DayGap)
+	}
+}

internal/executor/gitretime_test.go

@@ -327,3 +327,87 @@ func TestBuildPlanListsEachSqueezedDayOnce(t *testing.T) {
 		t.Errorf("squeezed day = %q", got)
 	}
 }
+
+func TestPlanRetimeRedateStartingFromDay(t *testing.T) {
+	// Three commits originally on 2026-10-01, re-dated from 2026-11-01 with one
+	// commit per day.
+	date := day(2026, 10, 1)
+	commits := []gitCommit{
+		commitAt("c1", date, 9, 0, 0),
+		commitAt("c2", date, 10, 0, 0),
+		commitAt("c3", date, 11, 0, 0),
+	}
+	opts := defaultRetimeOptions(3)
+	opts.StartDate = day(2026, 11, 1)
+	opts.PerDay = 1
+	opts.DayGap = 1
+
+	plan := planRetime(commits, opts)
+	if len(plan) != 3 {
+		t.Fatalf("plan has %d entries", len(plan))
+	}
+	for i, want := range []string{"2026-11-01", "2026-11-02", "2026-11-03"} {
+		got := plan[i].NewTime.In(cst).Format("2006-01-02")
+		if got != want {
+			t.Errorf("commit %d re-dated to %s, want %s", i+1, got, want)
+		}
+		if h := plan[i].NewTime.In(cst).Hour(); h < 21 || h > 22 {
+			t.Errorf("commit %d at hour %d, want 21-22", i+1, h)
+		}
+	}
+}
+
+func TestPlanRetimeRedateHonoursDayGap(t *testing.T) {
+	date := day(2026, 10, 1)
+	commits := []gitCommit{
+		commitAt("c1", date, 9, 0, 0),
+		commitAt("c2", date, 10, 0, 0),
+	}
+	opts := defaultRetimeOptions(4)
+	opts.StartDate = day(2026, 11, 1)
+	opts.PerDay = 1
+	opts.DayGap = 3
+
+	plan := planRetime(commits, opts)
+	if got := plan[1].NewTime.In(cst).Format("2006-01-02"); got != "2026-11-04" {
+		t.Fatalf("second commit on %s, want 2026-11-04 (gap 3 days)", got)
+	}
+}
+
+func TestPlanRetimeRedatePacksSeveralPerDay(t *testing.T) {
+	date := day(2026, 10, 1)
+	var commits []gitCommit
+	for i := 0; i < 4; i++ {
+		commits = append(commits, commitAt("c", date, 9, i, 0))
+	}
+	opts := defaultRetimeOptions(5)
+	opts.StartDate = day(2026, 11, 1)
+	opts.PerDay = 2
+	opts.DayGap = 1
+
+	plan := planRetime(commits, opts)
+	firstDay := plan[0].NewTime.In(cst).Format("2006-01-02")
+	secondOfFirstDay := plan[1].NewTime.In(cst).Format("2006-01-02")
+	thirdDay := plan[2].NewTime.In(cst).Format("2006-01-02")
+	if firstDay != "2026-11-01" || secondOfFirstDay != "2026-11-01" {
+		t.Fatalf("first two commits should share 2026-11-01, got %s and %s", firstDay, secondOfFirstDay)
+	}
+	if thirdDay != "2026-11-02" {
+		t.Fatalf("third commit on %s, want 2026-11-02", thirdDay)
+	}
+	// Within a day the times stay ordered.
+	if !plan[1].NewTime.After(plan[0].NewTime) {
+		t.Fatalf("same-day commits are not ordered: %v, %v", plan[0].NewTime, plan[1].NewTime)
+	}
+}
+
+func TestPlanRetimeWithoutStartDateKeepsOriginalDays(t *testing.T) {
+	commits := []gitCommit{
+		commitAt("c1", day(2026, 10, 1), 9, 0, 0),
+		commitAt("c2", day(2026, 10, 5), 9, 0, 0),
+	}
+	plan := planRetime(commits, defaultRetimeOptions(1))
+	if a, b := plan[0].NewTime.In(cst).Format("2006-01-02"), plan[1].NewTime.In(cst).Format("2006-01-02"); a != "2026-10-01" || b != "2026-10-05" {
+		t.Fatalf("original days changed: %s, %s", a, b)
+	}
+}