Re: [PATCH v2 2/4] commit-queue: LIFO or priority queue of commits

@@ -190,6 +190,7 @@
 /test-mktemp
 /test-parse-options
 /test-path-utils
+/test-prio-queue
 /test-regex
 /test-revision-walking
 /test-run-command

@@ -552,6 +552,7 @@ TEST_PROGRAMS_NEED_X += test-mergesort
 TEST_PROGRAMS_NEED_X += test-mktemp
 TEST_PROGRAMS_NEED_X += test-parse-options
 TEST_PROGRAMS_NEED_X += test-path-utils
+TEST_PROGRAMS_NEED_X += test-prio-queue
 TEST_PROGRAMS_NEED_X += test-regex
 TEST_PROGRAMS_NEED_X += test-revision-walking
 TEST_PROGRAMS_NEED_X += test-run-command

@@ -685,6 +686,7 @@ LIB_H += parse-options.h
 LIB_H += patch-ids.h
 LIB_H += pathspec.h
 LIB_H += pkt-line.h
+LIB_H += prio-queue.h
 LIB_H += progress.h
 LIB_H += prompt.h
 LIB_H += quote.h

@@ -824,6 +826,7 @@ LIB_OBJS += pathspec.o
 LIB_OBJS += pkt-line.o
 LIB_OBJS += preload-index.o
 LIB_OBJS += pretty.o
+LIB_OBJS += prio-queue.o
 LIB_OBJS += progress.o
 LIB_OBJS += prompt.o
 LIB_OBJS += quote.o

@@ -0,0 +1,71 @@
+#include "cache.h"
+#include "commit.h"
+#include "prio-queue.h"
+
+void clear_prio_queue(struct prio_queue *queue)
+{
+	free(queue->array);
+	queue->nr = 0;
+	queue->alloc = 0;
+	queue->array = NULL;
+}
+
+void prio_queue_put(struct prio_queue *queue, void *thing)
+{
+	prio_queue_compare_fn compare = queue->compare;
+	int ix, parent;
+
+	/* Append at the end */
+	ALLOC_GROW(queue->array, queue->nr + 1, queue->alloc);
+	queue->array[queue->nr++] = thing;
+	if (!compare)
+		return; /* LIFO */
+
+	/* Bubble up the new one */
+	for (ix = queue->nr - 1; ix; ix = parent) {
+		parent = (ix - 1) / 2;
+		if (compare(queue->array[parent], queue->array[ix],
+			    queue->cb_data) <= 0)
+			break;
+
+		thing = queue->array[parent];
+		queue->array[parent] = queue->array[ix];
+		queue->array[ix] = thing;
+	}
+}
+
+void *prio_queue_get(struct prio_queue *queue)
+{
+	void *result, *swap;
+	int ix, child;
+	prio_queue_compare_fn compare = queue->compare;
+
+	if (!queue->nr)
+		return NULL;
+	if (!compare)
+		return queue->array[--queue->nr]; /* LIFO */
+
+	result = queue->array[0];
+	if (!--queue->nr)
+		return result;
+
+	queue->array[0] = queue->array[queue->nr];
+
+	/* Push down the one at the root */
+	for (ix = 0; ix * 2 + 1 < queue->nr; ix = child) {
+		child = ix * 2 + 1; /* left */
+		if ((child + 1 < queue->nr) &&
+		    (compare(queue->array[child], queue->array[child + 1],
+			     queue->cb_data) >= 0))
+			child++; /* use right child */
+
+		if (compare(queue->array[ix], queue->array[child],
+			    queue->cb_data) <= 0)
+			break;
+
+		swap = queue->array[child];
+		queue->array[child] = queue->array[ix];
+		queue->array[ix] = swap;
+	}
+	return result;
+}

@@ -0,0 +1,45 @@
+#ifndef PRIO_QUEUE_H
+#define PRIO_QUEUE_H
+
+/*
+ * A priority queue implementation, primarily for keeping track of
+ * commits in the 'date-order' so that we process them from new to old
+ * as they are discovered, but can be used to hold any pointer to
+ * struct.  The caller is responsible for supplying a function to
+ * compare two "things".
+ *
+ * Alternatively, this data structure can also be used as a LIFO stack
+ * by specifying NULL as the comparison function.
+ */
+
+/*
+ * Compare two "things", one and two; the third parameter is cb_data
+ * in the prio_queue structure.  The result is returned as a sign of
+ * the return value, being the same as the sign of the result of
+ * subtracting "two" from "one" (i.e. negative if "one" sorts earlier
+ * than "two").
+ */
+typedef int (*prio_queue_compare_fn)(const void *one, const void *two, void *cb_data);
+
+struct prio_queue {
+	prio_queue_compare_fn compare;
+	void *cb_data;
+	int alloc, nr;
+	void **array;
+};
+
+/*
+ * Add the "thing" to the queue.
+ */
+extern void prio_queue_put(struct prio_queue *, void *thing);
+
+/*
+ * Extract the "thing" that compares the smallest out of the queue,
+ * or NULL.  If compare function is NULL, the queue acts as a LIFO
+ * stack.
+ */
+extern void *prio_queue_get(struct prio_queue *);
+
+extern void clear_prio_queue(struct prio_queue *);
+
+#endif /* PRIO_QUEUE_H */

@@ -0,0 +1,50 @@
+#!/bin/sh
+
+test_description='basic tests for priority queue implementation'
+. ./test-lib.sh
+
+cat >expect <<'EOF'
+1
+2
+3
+4
+5
+5
+6
+7
+8
+9
+10
+EOF
+test_expect_success 'basic ordering' '
+	test-prio-queue 2 6 3 10 9 5 7 4 5 8 1 dump >actual &&
+	test_cmp expect actual
+'
+
+cat >expect <<'EOF'
+2
+3
+4
+1
+5
+6
+EOF
+test_expect_success 'mixed put and get' '
+	test-prio-queue 6 2 4 get 5 3 get get 1 dump >actual &&
+	test_cmp expect actual
+'
+
+cat >expect <<'EOF'
+1
+2
+NULL
+1
+2
+NULL
+EOF
+test_expect_success 'notice empty queue' '
+	test-prio-queue 1 2 get get get 1 2 get get get >actual &&
+	test_cmp expect actual
+'
+
+test_done

@@ -0,0 +1,39 @@
+#include "cache.h"
+#include "prio-queue.h"
+
+static int intcmp(const void *va, const void *vb, void *data)
+{
+	const int *a = va, *b = vb;
+	return *a - *b;
+}
+
+static void show(int *v)
+{
+	if (!v)
+		printf("NULL\n");
+	else
+		printf("%d\n", *v);
+	free(v);
+}
+
+int main(int argc, char **argv)
+{
+	struct prio_queue pq = { intcmp };
+
+	while (*++argv) {
+		if (!strcmp(*argv, "get"))
+			show(prio_queue_get(&pq));
+		else if (!strcmp(*argv, "dump")) {
+			int *v;
+			while ((v = prio_queue_get(&pq)))
+			       show(v);
+		}
+		else {
+			int *v = malloc(sizeof(*v));
+			*v = atoi(*argv);
+			prio_queue_put(&pq, v);
+		}
+	}
+
+	return 0;
+}

@@ -205,7 +205,7 @@ static void log_show_early(struct rev_info *revs, struct commit_list *list)
 	int i = revs->early_output;
 	int show_header = 1;
 
-	sort_in_topological_order(&list, revs->lifo);
+	sort_in_topological_order(&list, revs->sort_order);
 	while (list && i) {
 		struct commit *commit = list->item;
 		switch (simplify_commit(revs, commit)) {

@@ -631,7 +631,7 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 	int num_rev, i, extra = 0;
 	int all_heads = 0, all_remotes = 0;
 	int all_mask, all_revs;
-	int lifo = 1;
+	enum rev_sort_order sort_order = REV_SORT_IN_GRAPH_ORDER;
 	char head[128];
 	const char *head_p;
 	int head_len;

@@ -666,15 +666,17 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 			    N_("show possible merge bases")),
 		OPT_BOOLEAN(0, "independent", &independent,
 			    N_("show refs unreachable from any other ref")),
-		OPT_BOOLEAN(0, "topo-order", &lifo,
-			    N_("show commits in topological order")),
+		OPT_SET_INT(0, "topo-order", &sort_order,
+			    N_("show commits in topological order"),
+			    REV_SORT_IN_GRAPH_ORDER),
 		OPT_BOOLEAN(0, "topics", &topics,
 			    N_("show only commits not on the first branch")),
 		OPT_SET_INT(0, "sparse", &dense,
 			    N_("show merges reachable from only one tip"), 0),
-		OPT_SET_INT(0, "date-order", &lifo,
+		OPT_SET_INT(0, "date-order", &sort_order,
 			    N_("show commits where no parent comes before its "
-			       "children"), 0),
+			       "children"),
+			    REV_SORT_BY_COMMIT_DATE),
 		{ OPTION_CALLBACK, 'g', "reflog", &reflog_base, N_("<n>[,<base>]"),
 			    N_("show <n> most recent ref-log entries starting at "
 			       "base"),

@@ -901,7 +903,7 @@ int cmd_show_branch(int ac, const char **av, const char *prefix)
 		exit(0);
 
 	/* Sort topologically */
-	sort_in_topological_order(&seen, lifo);
+	sort_in_topological_order(&seen, sort_order);
 
 	/* Give names to commits */
 	if (!sha1_name && !no_name)

@@ -512,7 +512,7 @@ define_commit_slab(indegree_slab, int);
 /*
  * Performs an in-place topological sort on the list supplied.
  */
-void sort_in_topological_order(struct commit_list ** list, int lifo)
+void sort_in_topological_order(struct commit_list ** list, enum rev_sort_order sort_order)
 {
 	struct commit_list *next, *orig = *list;
 	struct commit_list *work, **insert;

@@ -561,7 +561,7 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
 	}
 
 	/* process the list in topological order */
-	if (!lifo)
+	if (sort_order != REV_SORT_IN_GRAPH_ORDER)
 		commit_list_sort_by_date(&work);
 
 	pptr = list;

@@ -588,10 +588,14 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
 			 * guaranteeing topological order.
 			 */
 			if (--(*pi) == 1) {
-				if (!lifo)
+				switch (sort_order) {
+				case REV_SORT_BY_COMMIT_DATE:
 					commit_list_insert_by_date(parent, &work);
-				else
+					break;
+				default: /* REV_SORT_IN_GRAPH_ORDER */
 					commit_list_insert(parent, &work);
+					break;
+				}
 			}
 		}
 		/*

@@ -139,15 +139,23 @@ struct commit *pop_commit(struct commit_list **stack);
 void clear_commit_marks(struct commit *commit, unsigned int mark);
 void clear_commit_marks_for_object_array(struct object_array *a, unsigned mark);
 
+
+enum rev_sort_order {
+	REV_SORT_IN_GRAPH_ORDER = 0,
+	REV_SORT_BY_COMMIT_DATE
+};
+
 /*
  * Performs an in-place topological sort of list supplied.
  *
  *   invariant of resulting list is:
  *      a reachable from b => ord(b) < ord(a)
- *   in addition, when lifo == 0, commits on parallel tracks are
- *   sorted in the dates order.
+ *   sort_order further specifies:
+ *   REV_SORT_IN_GRAPH_ORDER: try to show a commit on a single-parent
+ *                            chain together.
+ *   REV_SORT_BY_COMMIT_DATE: show eligible commits in committer-date order.
  */
-void sort_in_topological_order(struct commit_list ** list, int lifo);
+void sort_in_topological_order(struct commit_list **, enum rev_sort_order);
 
 struct commit_graft {
 	unsigned char sha1[20];

@@ -1038,7 +1038,7 @@ void init_revisions(struct rev_info *revs, const char *prefix)
 	DIFF_OPT_SET(&revs->pruning, QUICK);
 	revs->pruning.add_remove = file_add_remove;
 	revs->pruning.change = file_change;
-	revs->lifo = 1;
+	revs->sort_order = REV_SORT_IN_GRAPH_ORDER;
 	revs->dense = 1;
 	revs->prefix = prefix;
 	revs->max_age = -1;

@@ -1373,7 +1373,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	} else if (!strcmp(arg, "--merge")) {
 		revs->show_merge = 1;
 	} else if (!strcmp(arg, "--topo-order")) {
-		revs->lifo = 1;
+		revs->sort_order = REV_SORT_IN_GRAPH_ORDER;
 		revs->topo_order = 1;
 	} else if (!strcmp(arg, "--simplify-merges")) {
 		revs->simplify_merges = 1;

@@ -1391,7 +1391,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 		revs->prune = 1;
 		load_ref_decorations(DECORATE_SHORT_REFS);
 	} else if (!strcmp(arg, "--date-order")) {
-		revs->lifo = 0;
+		revs->sort_order = REV_SORT_BY_COMMIT_DATE;
 		revs->topo_order = 1;
 	} else if (!prefixcmp(arg, "--early-output")) {
 		int count = 100;

@@ -2165,7 +2165,7 @@ int prepare_revision_walk(struct rev_info *revs)
 		if (limit_list(revs) < 0)
 			return -1;
 	if (revs->topo_order)
-		sort_in_topological_order(&revs->commits, revs->lifo);
+		sort_in_topological_order(&revs->commits, revs->sort_order);
 	if (revs->simplify_merges)
 		simplify_merges(revs);
 	if (revs->children.name)

@@ -2480,7 +2480,7 @@ static void create_boundary_commit_list(struct rev_info *revs)
 	 * If revs->topo_order is set, sort the boundary commits
 	 * in topological order
 	 */
-	sort_in_topological_order(&revs->commits, revs->lifo);
+	sort_in_topological_order(&revs->commits, revs->sort_order);
 }
 
 static struct commit *get_revision_internal(struct rev_info *revs)

@@ -4,6 +4,7 @@
 #include "parse-options.h"
 #include "grep.h"
 #include "notes.h"
+#include "commit.h"
 
 #define SEEN		(1u<<0)
 #define UNINTERESTING   (1u<<1)

@@ -60,6 +61,10 @@ struct rev_info {
 	const char *prefix;
 	const char *def;
 	struct pathspec prune_data;
+
+	/* topo-sort */
+	enum rev_sort_order sort_order;
+
 	unsigned int	early_output:1,
 			ignore_missing:1;
 

@@ -70,7 +75,6 @@ struct rev_info {
 			show_all:1,
 			remove_empty_trees:1,
 			simplify_history:1,
-			lifo:1,
 			topo_order:1,
 			simplify_merges:1,
 			simplify_by_decoration:1,

@@ -9,6 +9,7 @@
 #include "gpg-interface.h"
 #include "mergesort.h"
 #include "commit-slab.h"
+#include "prio-queue.h"
 
 static struct commit_extra_header *read_commit_extra_header_lines(const char *buf, size_t len, const char **);
 

@@ -509,21 +510,42 @@ struct commit *pop_commit(struct commit_list **stack)
 /* count number of children that have not been emitted */
 define_commit_slab(indegree_slab, int);
 
+static int compare_commits_by_commit_date(const void *a_, const void *b_, void *unused)
+{
+	const struct commit *a = a_, *b = b_;
+	/* newer commits with larger date first */
+	if (a->date < b->date)
+		return 1;
+	else if (a->date > b->date)
+		return -1;
+	return 0;
+}
+
 /*
  * Performs an in-place topological sort on the list supplied.
  */
-void sort_in_topological_order(struct commit_list ** list, enum rev_sort_order sort_order)
+void sort_in_topological_order(struct commit_list **list, enum rev_sort_order sort_order)
 {
 	struct commit_list *next, *orig = *list;
-	struct commit_list *work, **insert;
 	struct commit_list **pptr;
 	struct indegree_slab indegree;
+	struct prio_queue queue;
+	struct commit *commit;
 
 	if (!orig)
 		return;
 	*list = NULL;
 
 	init_indegree_slab(&indegree);
+	memset(&queue, '\0', sizeof(queue));
+	switch (sort_order) {
+	default: /* REV_SORT_IN_GRAPH_ORDER */
+		queue.compare = NULL;
+		break;
+	case REV_SORT_BY_COMMIT_DATE:
+		queue.compare = compare_commits_by_commit_date;
+		break;
+	}
 
 	/* Mark them and clear the indegree */
 	for (next = orig; next; next = next->next) {

@@ -533,7 +555,7 @@ void sort_in_topological_order(struct commit_list ** list, enum rev_sort_order s
 
 	/* update the indegree */
 	for (next = orig; next; next = next->next) {
-		struct commit_list * parents = next->item->parents;
+		struct commit_list *parents = next->item->parents;
 		while (parents) {
 			struct commit *parent = parents->item;
 			int *pi = indegree_slab_at(&indegree, parent);

@@ -551,30 +573,28 @@ void sort_in_topological_order(struct commit_list ** list, enum rev_sort_order s
 	 *
 	 * the tips serve as a starting set for the work queue.
 	 */
-	work = NULL;
-	insert = &work;
 	for (next = orig; next; next = next->next) {
 		struct commit *commit = next->item;
 
 		if (*(indegree_slab_at(&indegree, commit)) == 1)
-			insert = &commit_list_insert(commit, insert)->next;
+			prio_queue_put(&queue, commit);
 	}
 
-	/* process the list in topological order */
-	if (sort_order != REV_SORT_IN_GRAPH_ORDER)
-		commit_list_sort_by_date(&work);
+	/*
+	 * This is unfortunate; the initial tips need to be shown
+	 * in the order given from the revision traversal machinery.
+	 */
+	if (sort_order == REV_SORT_IN_GRAPH_ORDER)
+		prio_queue_reverse(&queue);
+
+	/* We no longer need the commit list */
+	free_commit_list(orig);
 
 	pptr = list;
 	*list = NULL;
-	while (work) {
-		struct commit *commit;
-		struct commit_list *parents, *work_item;
-
-		work_item = work;
-		work = work_item->next;
-		work_item->next = NULL;
+	while ((commit = prio_queue_get(&queue)) != NULL) {
+		struct commit_list *parents;
 
-		commit = work_item->item;
 		for (parents = commit->parents; parents ; parents = parents->next) {
 			struct commit *parent = parents->item;
 			int *pi = indegree_slab_at(&indegree, parent);

@@ -587,27 +607,20 @@ void sort_in_topological_order(struct commit_list ** list, enum rev_sort_order s
 			 * when all their children have been emitted thereby
 			 * guaranteeing topological order.
 			 */
-			if (--(*pi) == 1) {
-				switch (sort_order) {
-				case REV_SORT_BY_COMMIT_DATE:
-					commit_list_insert_by_date(parent, &work);
-					break;
-				default: /* REV_SORT_IN_GRAPH_ORDER */
-					commit_list_insert(parent, &work);
-					break;
-				}
-			}
+			if (--(*pi) == 1)
+				prio_queue_put(&queue, parent);
 		}
 		/*
-		 * work_item is a commit all of whose children
-		 * have already been emitted. we can emit it now.
+		 * all children of commit have already been
+		 * emitted. we can emit it now.
 		 */
 		*(indegree_slab_at(&indegree, commit)) = 0;
-		*pptr = work_item;
-		pptr = &work_item->next;
+
+		pptr = &commit_list_insert(commit, pptr)->next;
 	}
 
 	clear_indegree_slab(&indegree);
+	clear_prio_queue(&queue);
 }
 
 /* merge-base stuff */

@@ -2,6 +2,19 @@
 #include "commit.h"
 #include "prio-queue.h"
 
+void prio_queue_reverse(struct prio_queue *queue)
+{
+	int i, j;
+
+	if (queue->compare != NULL)
+		die("BUG: prio_queue_reverse() on non-LIFO queue");
+	for (i = 0; i <= (j = (queue->nr - 1) - i); i++) {
+		struct commit *swap = queue->array[i];
+		queue->array[i] = queue->array[j];
+		queue->array[j] = swap;
+	}
+}
+
 void clear_prio_queue(struct prio_queue *queue)
 {
 	free(queue->array);

@@ -42,4 +42,7 @@ extern void *prio_queue_get(struct prio_queue *);
 
 extern void clear_prio_queue(struct prio_queue *);
 
+/* Reverse the LIFO elements */
+extern void prio_queue_reverse(struct prio_queue *);
+
 #endif /* PRIO_QUEUE_H */

@@ -617,6 +617,10 @@ By default, the commits are shown in reverse chronological order.
 	Show no parents before all of its children are shown, but
 	otherwise show commits in the commit timestamp order.
 
+--author-date-order::
+	Show no parents before all of its children are shown, but
+	otherwise show commits in the author timestamp order.
+
 --topo-order::
 	Show no parents before all of its children are shown, and
 	avoid showing commits on multiple lines of history

@@ -510,6 +510,68 @@ struct commit *pop_commit(struct commit_list **stack)
 /* count number of children that have not been emitted */
 define_commit_slab(indegree_slab, int);
 
+/* record author-date for each commit object */
+define_commit_slab(author_date_slab, unsigned long);
+
+static void record_author_date(struct author_date_slab *author_date,
+			       struct commit *commit)
+{
+	const char *buf, *line_end;
+	char *buffer = NULL;
+	struct ident_split ident;
+	char *date_end;
+	unsigned long date;
+
+	if (!commit->buffer) {
+		unsigned long size;
+		enum object_type type;
+		buffer = read_sha1_file(commit->object.sha1, &type, &size);
+		if (!buffer)
+			return;
+	}
+
+	for (buf = commit->buffer ? commit->buffer : buffer;
+	     buf;
+	     buf = line_end + 1) {
+		line_end = strchrnul(buf, '\n');
+		if (prefixcmp(buf, "author ")) {
+			if (!line_end[0] || line_end[1] == '\n')
+				return; /* end of header */
+			continue;
+		}
+		if (split_ident_line(&ident,
+				     buf + strlen("author "),
+				     line_end - (buf + strlen("author "))) ||
+		    !ident.date_begin || !ident.date_end)
+			goto fail_exit; /* malformed "author" line */
+		break;
+	}
+
+	date = strtoul(ident.date_begin, &date_end, 10);
+	if (date_end != ident.date_end)
+		goto fail_exit; /* malformed date */
+	*(author_date_slab_at(author_date, commit)) = date;
+
+fail_exit:
+	free(buffer);
+}
+
+static int compare_commits_by_author_date(const void *a_, const void *b_,
+					  void *cb_data)
+{
+	const struct commit *a = a_, *b = b_;
+	struct author_date_slab *author_date = cb_data;
+	unsigned long a_date = *(author_date_slab_at(author_date, a));
+	unsigned long b_date = *(author_date_slab_at(author_date, b));
+
+	/* newer commits with larger date first */
+	if (a_date < b_date)
+		return 1;
+	else if (a_date > b_date)
+		return -1;
+	return 0;
+}
+
 static int compare_commits_by_commit_date(const void *a_, const void *b_, void *unused)
 {
 	const struct commit *a = a_, *b = b_;

@@ -531,6 +593,7 @@ void sort_in_topological_order(struct commit_list **list, enum rev_sort_order so
 	struct indegree_slab indegree;
 	struct prio_queue queue;
 	struct commit *commit;
+	struct author_date_slab author_date;
 
 	if (!orig)
 		return;

@@ -538,6 +601,7 @@ void sort_in_topological_order(struct commit_list **list, enum rev_sort_order so
 
 	init_indegree_slab(&indegree);
 	memset(&queue, '\0', sizeof(queue));
+
 	switch (sort_order) {
 	default: /* REV_SORT_IN_GRAPH_ORDER */
 		queue.compare = NULL;

@@ -545,12 +609,20 @@ void sort_in_topological_order(struct commit_list **list, enum rev_sort_order so
 	case REV_SORT_BY_COMMIT_DATE:
 		queue.compare = compare_commits_by_commit_date;
 		break;
+	case REV_SORT_BY_AUTHOR_DATE:
+		init_author_date_slab(&author_date);
+		queue.compare = compare_commits_by_author_date;
+		queue.cb_data = &author_date;
+		break;
 	}
 
 	/* Mark them and clear the indegree */
 	for (next = orig; next; next = next->next) {
 		struct commit *commit = next->item;
 		*(indegree_slab_at(&indegree, commit)) = 1;
+		/* also record the author dates, if needed */
+		if (sort_order == REV_SORT_BY_AUTHOR_DATE)
+			record_author_date(&author_date, commit);
 	}
 
 	/* update the indegree */

@@ -621,6 +693,8 @@ void sort_in_topological_order(struct commit_list **list, enum rev_sort_order so
 
 	clear_indegree_slab(&indegree);
 	clear_prio_queue(&queue);
+	if (sort_order == REV_SORT_BY_AUTHOR_DATE)
+		clear_author_date_slab(&author_date);
 }
 
 /* merge-base stuff */

@@ -142,7 +142,8 @@ void clear_commit_marks_for_object_array(struct object_array *a, unsigned mark);
 
 enum rev_sort_order {
 	REV_SORT_IN_GRAPH_ORDER = 0,
-	REV_SORT_BY_COMMIT_DATE
+	REV_SORT_BY_COMMIT_DATE,
+	REV_SORT_BY_AUTHOR_DATE
 };
 
 /*

@@ -1393,6 +1393,9 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	} else if (!strcmp(arg, "--date-order")) {
 		revs->sort_order = REV_SORT_BY_COMMIT_DATE;
 		revs->topo_order = 1;
+	} else if (!strcmp(arg, "--author-date-order")) {
+		revs->sort_order = REV_SORT_BY_AUTHOR_DATE;
+		revs->topo_order = 1;
 	} else if (!prefixcmp(arg, "--early-output")) {
 		int count = 100;
 		switch (arg[14]) {