Merge branch 'jc/topo-author-date-sort'

"git log" learned the "--author-date-order" option, with which the
output is topologically sorted and commits in parallel histories
are shown intermixed together based on the author timestamp.

* jc/topo-author-date-sort:
  t6003: add --author-date-order test
  topology tests: teach a helper to set author dates as well
  t6003: add --date-order test
  topology tests: teach a helper to take abbreviated timestamps
  t/lib-t6000: style fixes
  log: --author-date-order
  sort-in-topological-order: use prio-queue
  prio-queue: priority queue of pointers to structs
  toposort: rename "lifo" field

1 files changed, 118 insertions, 27 deletions

diff --git a/commit.c b/commit.c
index a1096a2b5a..521e49c309 100644
--- a/commit.c
+++ b/commit.c
@@ -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 **);
 
@@ -518,31 +519,124 @@ 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_;
+	/* 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, 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;
 	struct commit_list **pptr;
 	struct indegree_slab indegree;
+	struct prio_queue queue;
+	struct commit *commit;
+	struct author_date_slab author_date;
 
 	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;
+	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 */
 	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);
@@ -560,30 +654,28 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
 	 *
 	 * 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 (!lifo)
-		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);
@@ -596,23 +688,22 @@ void sort_in_topological_order(struct commit_list ** list, int lifo)
 			 * when all their children have been emitted thereby
 			 * guaranteeing topological order.
 			 */
-			if (--(*pi) == 1) {
-				if (!lifo)
-					commit_list_insert_by_date(parent, &work);
-				else
-					commit_list_insert(parent, &work);
-			}
+			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);
+	if (sort_order == REV_SORT_BY_AUTHOR_DATE)
+		clear_author_date_slab(&author_date);
 }
 
 /* merge-base stuff */