Merge branch 'lt/rev-list' into next

* lt/rev-list:
  setup_revisions(): handle -n<n> and -<n> internally.
  git-log (internal): more options.
  git-log (internal): add approxidate.
  Rip out merge-order and make "git log <paths>..." work again.
  Tie it all together: "git log"
  Introduce trivial new pager.c helper infrastructure
  git-rev-list libification: rev-list walking
  Splitting rev-list into revisions lib, end of beginning.
  rev-list split: minimum fixup.
  First cut at libifying revlist generation

14 files changed, 954 insertions, 1886 deletions

diff --git a/Documentation/git-rev-list.txt b/Documentation/git-rev-list.txt
index 27f18e2c50..8255ae1bce 100644
--- a/Documentation/git-rev-list.txt
+++ b/Documentation/git-rev-list.txt
@@ -16,7 +16,7 @@ SYNOPSIS
 	     [ \--no-merges ]
 	     [ \--remove-empty ]
 	     [ \--all ]
-	     [ [ \--merge-order [ \--show-breaks ] ] | [ \--topo-order ] ]
+	     [ \--topo-order ]
 	     [ \--parents ]
 	     [ [\--objects | \--objects-edge] [ \--unpacked ] ]
 	     [ \--pretty | \--header ]
@@ -102,57 +102,10 @@ OPTIONS
 	topological order (i.e. descendant commits are shown
 	before their parents).
 
---merge-order::
-	When specified the commit history is decomposed into a unique
-	sequence of minimal, non-linear epochs and maximal, linear epochs.
-	Non-linear epochs are then linearised by sorting them into merge
-	order, which is described below.
-+
-Maximal, linear epochs correspond to periods of sequential development.
-Minimal, non-linear epochs correspond to periods of divergent development
-followed by a converging merge. The theory of epochs is described in more
-detail at
-link:http://blackcubes.dyndns.org/epoch/[http://blackcubes.dyndns.org/epoch/].
-+
-The merge order for a non-linear epoch is defined as a linearisation for which
-the following invariants are true:
-+
-    1. if a commit P is reachable from commit N, commit P sorts after commit N
-       in the linearised list.
-    2. if Pi and Pj are any two parents of a merge M (with i < j), then any
-       commit N, such that N is reachable from Pj but not reachable from Pi,
-       sorts before all commits reachable from Pi.
-+
-Invariant 1 states that later commits appear before earlier commits they are
-derived from.
-+
-Invariant 2 states that commits unique to "later" parents in a merge, appear
-before all commits from "earlier" parents of a merge.
-
---show-breaks::
-	Each item of the list is output with a 2-character prefix consisting
-	of one of: (|), (^), (=) followed by a space.
-+
-Commits marked with (=) represent the boundaries of minimal, non-linear epochs
-and correspond either to the start of a period of divergent development or to
-the end of such a period.
-+
-Commits marked with (|) are direct parents of commits immediately preceding
-the marked commit in the list.
-+
-Commits marked with (^) are not parents of the immediately preceding commit.
-These "breaks" represent necessary discontinuities implied by trying to
-represent an arbitrary DAG in a linear form.
-+
-`--show-breaks` is only valid if `--merge-order` is also specified.
-
-
 Author
 ------
 Written by Linus Torvalds <torvalds@osdl.org>
 
-Original *--merge-order* logic by Jon Seymour <jon.seymour@gmail.com>
-
 Documentation
 --------------
 Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>.
diff --git a/INSTALL b/INSTALL
index 433449fd8e..63af8eccf3 100644
--- a/INSTALL
+++ b/INSTALL
@@ -40,9 +40,7 @@ Issues of note:
 
 	  If you don't have openssl, you can use one of the SHA1 libraries
 	  that come with git (git includes the one from Mozilla, and has
-	  its own PowerPC-optimized one too - see the Makefile), and you
-	  can avoid the bignum support by excising git-rev-list support
-	  for "--merge-order" (by hand).
+	  its own PowerPC and ARM optimized ones too - see the Makefile).
 
 	- "libcurl" and "curl" executable.  git-http-fetch and
 	  git-fetch use them.  If you do not use http
diff --git a/Makefile b/Makefile
index a5eb0c4beb..a1ec04e3a0 100644
--- a/Makefile
+++ b/Makefile
@@ -6,8 +6,8 @@ all:
 # on non-x86 architectures (e.g. PowerPC), while the OpenSSL version (default
 # choice) has very fast version optimized for i586.
 #
-# Define NO_OPENSSL environment variable if you do not have OpenSSL. You will
-# miss out git-rev-list --merge-order. This also implies MOZILLA_SHA1.
+# Define NO_OPENSSL environment variable if you do not have OpenSSL.
+# This also implies MOZILLA_SHA1.
 #
 # Define NO_CURL if you do not have curl installed.  git-http-pull and
 # git-http-push are not built, and you cannot use http:// and https://
@@ -191,8 +191,8 @@ LIB_FILE=libgit.a
 
 LIB_H = \
 	blob.h cache.h commit.h count-delta.h csum-file.h delta.h \
-	diff.h epoch.h object.h pack.h pkt-line.h quote.h refs.h \
-	run-command.h strbuf.h tag.h tree.h git-compat-util.h
+	diff.h object.h pack.h pkt-line.h quote.h refs.h \
+	run-command.h strbuf.h tag.h tree.h git-compat-util.h revision.h
 
 DIFF_OBJS = \
 	diff.o diffcore-break.o diffcore-order.o diffcore-pathspec.o \
@@ -206,7 +206,7 @@ LIB_OBJS = \
 	quote.o read-cache.o refs.o run-command.o \
 	server-info.o setup.o sha1_file.o sha1_name.o strbuf.o \
 	tag.o tree.o usage.o config.o environment.o ctype.o copy.o \
-	fetch-clone.o \
+	fetch-clone.o revision.o pager.o \
 	$(DIFF_OBJS)
 
 LIBS = $(LIB_FILE)
@@ -329,7 +329,6 @@ ifndef NO_CURL
 endif
 
 ifndef NO_OPENSSL
-	LIB_OBJS += epoch.o
 	OPENSSL_LIBSSL = -lssl
 	ifdef OPENSSLDIR
 		# Again this may be problematic -- gcc does not always want -R.
@@ -455,7 +454,7 @@ strip: $(PROGRAMS) git$X
 
 git$X: git.c $(LIB_FILE)
 	$(CC) -DGIT_VERSION='"$(GIT_VERSION)"' \
-		$(CFLAGS) $(COMPAT_CFLAGS) -o $@ $(filter %.c,$^) $(LIB_FILE)
+		$(ALL_CFLAGS) -o $@ $(filter %.c,$^) $(LIB_FILE) $(LIBS)
 
 $(patsubst %.sh,%,$(SCRIPT_SH)) : % : %.sh
 	rm -f $@
diff --git a/cache.h b/cache.h
index 0d3b244ddd..8dc1de16e4 100644
--- a/cache.h
+++ b/cache.h
@@ -354,4 +354,7 @@ extern int copy_fd(int ifd, int ofd);
 extern int receive_unpack_pack(int fd[2], const char *me, int quiet);
 extern int receive_keep_pack(int fd[2], const char *me, int quiet);
 
+/* pager.c */
+extern void setup_pager(void);
+
 #endif /* CACHE_H */
diff --git a/epoch.c b/epoch.c
deleted file mode 100644
index 3a767486da..0000000000
--- a/epoch.c
+++ /dev/null
@@ -1,639 +0,0 @@
-/*
- * Copyright (c) 2005, Jon Seymour
- *
- * For more information about epoch theory on which this module is based,
- * refer to http://blackcubes.dyndns.org/epoch/. That web page defines
- * terms such as "epoch" and "minimal, non-linear epoch" and provides rationales
- * for some of the algorithms used here.
- *
- */
-#include <stdlib.h>
-
-/* Provides arbitrary precision integers required to accurately represent
- * fractional mass: */
-#include <openssl/bn.h>
-
-#include "cache.h"
-#include "commit.h"
-#include "epoch.h"
-
-struct fraction {
-	BIGNUM numerator;
-	BIGNUM denominator;
-};
-
-#define HAS_EXACTLY_ONE_PARENT(n) ((n)->parents && !(n)->parents->next)
-
-static BN_CTX *context = NULL;
-static struct fraction *one = NULL;
-static struct fraction *zero = NULL;
-
-static BN_CTX *get_BN_CTX(void)
-{
-	if (!context) {
-		context = BN_CTX_new();
-	}
-	return context;
-}
-
-static struct fraction *new_zero(void)
-{
-	struct fraction *result = xmalloc(sizeof(*result));
-	BN_init(&result->numerator);
-	BN_init(&result->denominator);
-	BN_zero(&result->numerator);
-	BN_one(&result->denominator);
-	return result;
-}
-
-static void clear_fraction(struct fraction *fraction)
-{
-	BN_clear(&fraction->numerator);
-	BN_clear(&fraction->denominator);
-}
-
-static struct fraction *divide(struct fraction *result, struct fraction *fraction, int divisor)
-{
-	BIGNUM bn_divisor;
-
-	BN_init(&bn_divisor);
-	BN_set_word(&bn_divisor, divisor);
-
-	BN_copy(&result->numerator, &fraction->numerator);
-	BN_mul(&result->denominator, &fraction->denominator, &bn_divisor, get_BN_CTX());
-
-	BN_clear(&bn_divisor);
-	return result;
-}
-
-static struct fraction *init_fraction(struct fraction *fraction)
-{
-	BN_init(&fraction->numerator);
-	BN_init(&fraction->denominator);
-	BN_zero(&fraction->numerator);
-	BN_one(&fraction->denominator);
-	return fraction;
-}
-
-static struct fraction *get_one(void)
-{
-	if (!one) {
-		one = new_zero();
-		BN_one(&one->numerator);
-	}
-	return one;
-}
-
-static struct fraction *get_zero(void)
-{
-	if (!zero) {
-		zero = new_zero();
-	}
-	return zero;
-}
-
-static struct fraction *copy(struct fraction *to, struct fraction *from)
-{
-	BN_copy(&to->numerator, &from->numerator);
-	BN_copy(&to->denominator, &from->denominator);
-	return to;
-}
-
-static struct fraction *add(struct fraction *result, struct fraction *left, struct fraction *right)
-{
-	BIGNUM a, b, gcd;
-
-	BN_init(&a);
-	BN_init(&b);
-	BN_init(&gcd);
-
-	BN_mul(&a, &left->numerator, &right->denominator, get_BN_CTX());
-	BN_mul(&b, &left->denominator, &right->numerator, get_BN_CTX());
-	BN_mul(&result->denominator, &left->denominator, &right->denominator, get_BN_CTX());
-	BN_add(&result->numerator, &a, &b);
-
-	BN_gcd(&gcd, &result->denominator, &result->numerator, get_BN_CTX());
-	BN_div(&result->denominator, NULL, &result->denominator, &gcd, get_BN_CTX());
-	BN_div(&result->numerator, NULL, &result->numerator, &gcd, get_BN_CTX());
-
-	BN_clear(&a);
-	BN_clear(&b);
-	BN_clear(&gcd);
-
-	return result;
-}
-
-static int compare(struct fraction *left, struct fraction *right)
-{
-	BIGNUM a, b;
-	int result;
-
-	BN_init(&a);
-	BN_init(&b);
-
-	BN_mul(&a, &left->numerator, &right->denominator, get_BN_CTX());
-	BN_mul(&b, &left->denominator, &right->numerator, get_BN_CTX());
-
-	result = BN_cmp(&a, &b);
-
-	BN_clear(&a);
-	BN_clear(&b);
-
-	return result;
-}
-
-struct mass_counter {
-	struct fraction seen;
-	struct fraction pending;
-};
-
-static struct mass_counter *new_mass_counter(struct commit *commit, struct fraction *pending)
-{
-	struct mass_counter *mass_counter = xmalloc(sizeof(*mass_counter));
-	memset(mass_counter, 0, sizeof(*mass_counter));
-
-	init_fraction(&mass_counter->seen);
-	init_fraction(&mass_counter->pending);
-
-	copy(&mass_counter->pending, pending);
-	copy(&mass_counter->seen, get_zero());
-
-	if (commit->object.util) {
-		die("multiple attempts to initialize mass counter for %s",
-		    sha1_to_hex(commit->object.sha1));
-	}
-
-	commit->object.util = mass_counter;
-
-	return mass_counter;
-}
-
-static void free_mass_counter(struct mass_counter *counter)
-{
-	clear_fraction(&counter->seen);
-	clear_fraction(&counter->pending);
-	free(counter);
-}
-
-/*
- * Finds the base commit of a list of commits.
- *
- * One property of the commit being searched for is that every commit reachable
- * from the base commit is reachable from the commits in the starting list only
- * via paths that include the base commit.
- *
- * This algorithm uses a conservation of mass approach to find the base commit.
- *
- * We start by injecting one unit of mass into the graph at each
- * of the commits in the starting list. Injecting mass into a commit
- * is achieved by adding to its pending mass counter and, if it is not already
- * enqueued, enqueuing the commit in a list of pending commits, in latest
- * commit date first order.
- *
- * The algorithm then proceeds to visit each commit in the pending queue.
- * Upon each visit, the pending mass is added to the mass already seen for that
- * commit and then divided into N equal portions, where N is the number of
- * parents of the commit being visited. The divided portions are then injected
- * into each of the parents.
- *
- * The algorithm continues until we discover a commit which has seen all the
- * mass originally injected or until we run out of things to do.
- *
- * If we find a commit that has seen all the original mass, we have found
- * the common base of all the commits in the starting list.
- *
- * The algorithm does _not_ depend on accurate timestamps for correct operation.
- * However, reasonably sane (e.g. non-random) timestamps are required in order
- * to prevent an exponential performance characteristic. The occasional
- * timestamp inaccuracy will not dramatically affect performance but may
- * result in more nodes being processed than strictly necessary.
- *
- * This procedure sets *boundary to the address of the base commit. It returns
- * non-zero if, and only if, there was a problem parsing one of the
- * commits discovered during the traversal.
- */
-static int find_base_for_list(struct commit_list *list, struct commit **boundary)
-{
-	int ret = 0;
-	struct commit_list *cleaner = NULL;
-	struct commit_list *pending = NULL;
-	struct fraction injected;
-	init_fraction(&injected);
-	*boundary = NULL;
-
-	for (; list; list = list->next) {
-		struct commit *item = list->item;
-
-		if (!item->object.util) {
-			new_mass_counter(list->item, get_one());
-			add(&injected, &injected, get_one());
-
-			commit_list_insert(list->item, &cleaner);
-			commit_list_insert(list->item, &pending);
-		}
-	}
-
-	while (!*boundary && pending && !ret) {
-		struct commit *latest = pop_commit(&pending);
-		struct mass_counter *latest_node = (struct mass_counter *) latest->object.util;
-		int num_parents;
-
-		if ((ret = parse_commit(latest)))
-			continue;
-		add(&latest_node->seen, &latest_node->seen, &latest_node->pending);
-
-		num_parents = count_parents(latest);
-		if (num_parents) {
-			struct fraction distribution;
-			struct commit_list *parents;
-
-			divide(init_fraction(&distribution), &latest_node->pending, num_parents);
-
-			for (parents = latest->parents; parents; parents = parents->next) {
-				struct commit *parent = parents->item;
-				struct mass_counter *parent_node = (struct mass_counter *) parent->object.util;
-
-				if (!parent_node) {
-					parent_node = new_mass_counter(parent, &distribution);
-					insert_by_date(parent, &pending);
-					commit_list_insert(parent, &cleaner);
-				} else {
-					if (!compare(&parent_node->pending, get_zero()))
-						insert_by_date(parent, &pending);
-					add(&parent_node->pending, &parent_node->pending, &distribution);
-				}
-			}
-
-			clear_fraction(&distribution);
-		}
-
-		if (!compare(&latest_node->seen, &injected))
-			*boundary = latest;
-		copy(&latest_node->pending, get_zero());
-	}
-
-	while (cleaner) {
-		struct commit *next = pop_commit(&cleaner);
-		free_mass_counter((struct mass_counter *) next->object.util);
-		next->object.util = NULL;
-	}
-
-	if (pending)
-		free_commit_list(pending);
-
-	clear_fraction(&injected);
-	return ret;
-}
-
-
-/*
- * Finds the base of an minimal, non-linear epoch, headed at head, by
- * applying the find_base_for_list to a list consisting of the parents
- */
-static int find_base(struct commit *head, struct commit **boundary)
-{
-	int ret = 0;
-	struct commit_list *pending = NULL;
-	struct commit_list *next;
-
-	for (next = head->parents; next; next = next->next) {
-		commit_list_insert(next->item, &pending);
-	}
-	ret = find_base_for_list(pending, boundary);
-	free_commit_list(pending);
-
-	return ret;
-}
-
-/*
- * This procedure traverses to the boundary of the first epoch in the epoch
- * sequence of the epoch headed at head_of_epoch. This is either the end of
- * the maximal linear epoch or the base of a minimal non-linear epoch.
- *
- * The queue of pending nodes is sorted in reverse date order and each node
- * is currently in the queue at most once.
- */
-static int find_next_epoch_boundary(struct commit *head_of_epoch, struct commit **boundary)
-{
-	int ret;
-	struct commit *item = head_of_epoch;
-
-	ret = parse_commit(item);
-	if (ret)
-		return ret;
-
-	if (HAS_EXACTLY_ONE_PARENT(item)) {
-		/*
-		 * We are at the start of a maximimal linear epoch.
-		 * Traverse to the end.
-		 */
-		while (HAS_EXACTLY_ONE_PARENT(item) && !ret) {
-			item = item->parents->item;
-			ret = parse_commit(item);
-		}
-		*boundary = item;
-
-	} else {
-		/*
-		 * Otherwise, we are at the start of a minimal, non-linear
-		 * epoch - find the common base of all parents.
-		 */
-		ret = find_base(item, boundary);
-	}
-
-	return ret;
-}
-
-/*
- * Returns non-zero if parent is known to be a parent of child.
- */
-static int is_parent_of(struct commit *parent, struct commit *child)
-{
-	struct commit_list *parents;
-	for (parents = child->parents; parents; parents = parents->next) {
-		if (!memcmp(parent->object.sha1, parents->item->object.sha1,
-		            sizeof(parents->item->object.sha1)))
-			return 1;
-	}
-	return 0;
-}
-
-/*
- * Pushes an item onto the merge order stack. If the top of the stack is
- * marked as being a possible "break", we check to see whether it actually
- * is a break.
- */
-static void push_onto_merge_order_stack(struct commit_list **stack, struct commit *item)
-{
-	struct commit_list *top = *stack;
-	if (top && (top->item->object.flags & DISCONTINUITY)) {
-		if (is_parent_of(top->item, item)) {
-			top->item->object.flags &= ~DISCONTINUITY;
-		}
-	}
-	commit_list_insert(item, stack);
-}
-
-/*
- * Marks all interesting, visited commits reachable from this commit
- * as uninteresting. We stop recursing when we reach the epoch boundary,
- * an unvisited node or a node that has already been marking uninteresting.
- *
- * This doesn't actually mark all ancestors between the start node and the
- * epoch boundary uninteresting, but does ensure that they will eventually
- * be marked uninteresting when the main sort_first_epoch() traversal
- * eventually reaches them.
- */
-static void mark_ancestors_uninteresting(struct commit *commit)
-{
-	unsigned int flags = commit->object.flags;
-	int visited = flags & VISITED;
-	int boundary = flags & BOUNDARY;
-	int uninteresting = flags & UNINTERESTING;
-	struct commit_list *next;
-
-	commit->object.flags |= UNINTERESTING;
-
-	/*
-	 * We only need to recurse if
-	 *      we are not on the boundary and
-	 *      we have not already been marked uninteresting and
-	 *      we have already been visited.
-	 *
-	 * The main sort_first_epoch traverse will mark unreachable
-	 * all uninteresting, unvisited parents as they are visited
-	 * so there is no need to duplicate that traversal here.
-	 *
-	 * Similarly, if we are already marked uninteresting
-	 * then either all ancestors have already been marked
-	 * uninteresting or will be once the sort_first_epoch
-	 * traverse reaches them.
-	 */
-
-	if (uninteresting || boundary || !visited)
-		return;
-
-	for (next = commit->parents; next; next = next->next)
-		mark_ancestors_uninteresting(next->item);
-}
-
-/*
- * Sorts the nodes of the first epoch of the epoch sequence of the epoch headed at head
- * into merge order.
- */
-static void sort_first_epoch(struct commit *head, struct commit_list **stack)
-{
-	struct commit_list *parents;
-
-	head->object.flags |= VISITED;
-
-	/*
-	 * TODO: By sorting the parents in a different order, we can alter the
-	 * merge order to show contemporaneous changes in parallel branches
-	 * occurring after "local" changes. This is useful for a developer
-	 * when a developer wants to see all changes that were incorporated
-	 * into the same merge as her own changes occur after her own
-	 * changes.
-	 */
-
-	for (parents = head->parents; parents; parents = parents->next) {
-		struct commit *parent = parents->item;
-
-		if (head->object.flags & UNINTERESTING) {
-			/*
-			 * Propagates the uninteresting bit to all parents.
-			 * if we have already visited this parent, then
-			 * the uninteresting bit will be propagated to each
-			 * reachable commit that is still not marked
-			 * uninteresting and won't otherwise be reached.
-			 */
-			mark_ancestors_uninteresting(parent);
-		}
-
-		if (!(parent->object.flags & VISITED)) {
-			if (parent->object.flags & BOUNDARY) {
-				if (*stack) {
-					die("something else is on the stack - %s",
-					    sha1_to_hex((*stack)->item->object.sha1));
-				}
-				push_onto_merge_order_stack(stack, parent);
-				parent->object.flags |= VISITED;
-
-			} else {
-				sort_first_epoch(parent, stack);
-				if (parents) {
-					/*
-					 * This indicates a possible
-					 * discontinuity it may not be be
-					 * actual discontinuity if the head
-					 * of parent N happens to be the tail
-					 * of parent N+1.
-					 *
-					 * The next push onto the stack will
-					 * resolve the question.
-					 */
-					(*stack)->item->object.flags |= DISCONTINUITY;
-				}
-			}
-		}
-	}
-
-	push_onto_merge_order_stack(stack, head);
-}
-
-/*
- * Emit the contents of the stack.
- *
- * The stack is freed and replaced by NULL.
- *
- * Sets the return value to STOP if no further output should be generated.
- */
-static int emit_stack(struct commit_list **stack, emitter_func emitter, int include_last)
-{
-	unsigned int seen = 0;
-	int action = CONTINUE;
-
-	while (*stack && (action != STOP)) {
-		struct commit *next = pop_commit(stack);
-		seen |= next->object.flags;
-		if (*stack || include_last) {
-			if (!*stack) 
-				next->object.flags |= BOUNDARY;
-			action = emitter(next);
-		}
-	}
-
-	if (*stack) {
-		free_commit_list(*stack);
-		*stack = NULL;
-	}
-
-	return (action == STOP || (seen & UNINTERESTING)) ? STOP : CONTINUE;
-}
-
-/*
- * Sorts an arbitrary epoch into merge order by sorting each epoch
- * of its epoch sequence into order.
- *
- * Note: this algorithm currently leaves traces of its execution in the
- * object flags of nodes it discovers. This should probably be fixed.
- */
-static int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitter)
-{
-	struct commit *next = head_of_epoch;
-	int ret = 0;
-	int action = CONTINUE;
-
-	ret = parse_commit(head_of_epoch);
-
-	next->object.flags |= BOUNDARY;
-
-	while (next && next->parents && !ret && (action != STOP)) {
-		struct commit *base = NULL;
-
-		ret = find_next_epoch_boundary(next, &base);
-		if (ret)
-			return ret;
-		next->object.flags |= BOUNDARY;
-		if (base)
-			base->object.flags |= BOUNDARY;
-
-		if (HAS_EXACTLY_ONE_PARENT(next)) {
-			while (HAS_EXACTLY_ONE_PARENT(next)
-			       && (action != STOP)
-			       && !ret) {
-				if (next->object.flags & UNINTERESTING) {
-					action = STOP;
-				} else {
-					action = emitter(next);
-				}
-				if (action != STOP) {
-					next = next->parents->item;
-					ret = parse_commit(next);
-				}
-			}
-
-		} else {
-			struct commit_list *stack = NULL;
-			sort_first_epoch(next, &stack);
-			action = emit_stack(&stack, emitter, (base == NULL));
-			next = base;
-		}
-	}
-
-	if (next && (action != STOP) && !ret) {
-		emitter(next);
-	}
-
-	return ret;
-}
-
-/*
- * Sorts the nodes reachable from a starting list in merge order, we
- * first find the base for the starting list and then sort all nodes
- * in this subgraph using the sort_first_epoch algorithm. Once we have
- * reached the base we can continue sorting using sort_in_merge_order.
- */
-int sort_list_in_merge_order(struct commit_list *list, emitter_func emitter)
-{
-	struct commit_list *stack = NULL;
-	struct commit *base;
-	int ret = 0;
-	int action = CONTINUE;
-	struct commit_list *reversed = NULL;
-
-	for (; list; list = list->next)
-		commit_list_insert(list->item, &reversed);
-
-	if (!reversed)
-		return ret;
-	else if (!reversed->next) {
-		/*
-		 * If there is only one element in the list, we can sort it
-		 * using sort_in_merge_order.
-		 */
-		base = reversed->item;
-	} else {
-		/*
-		 * Otherwise, we search for the base of the list.
-		 */
-		ret = find_base_for_list(reversed, &base);
-		if (ret)
-			return ret;
-		if (base)
-			base->object.flags |= BOUNDARY;
-
-		while (reversed) {
-			struct commit * next = pop_commit(&reversed);
-
-			if (!(next->object.flags & VISITED) && next!=base) {
-				sort_first_epoch(next, &stack);
-				if (reversed) {
-					/*
-					 * If we have more commits 
-					 * to push, then the first
-					 * push for the next parent may 
-					 * (or may * not) represent a 
-					 * discontinuity with respect
-					 * to the parent currently on 
-					 * the top of the stack.
-					 *
-					 * Mark it for checking here, 
-					 * and check it with the next 
-					 * push. See sort_first_epoch()
-					 * for more details.
-					 */
-					stack->item->object.flags |= DISCONTINUITY;
-				}
-			}
-		}
-
-		action = emit_stack(&stack, emitter, (base==NULL));
-	}
-
-	if (base && (action != STOP)) {
-		ret = sort_in_merge_order(base, emitter);
-	}
-
-	return ret;
-}
diff --git a/epoch.h b/epoch.h
deleted file mode 100644
index 7493d5a241..0000000000
--- a/epoch.h
+++ /dev/null
@@ -1,21 +0,0 @@
-#ifndef EPOCH_H
-#define EPOCH_H
-
-
-// return codes for emitter_func
-#define STOP     0
-#define CONTINUE 1
-#define DO       2
-typedef int (*emitter_func) (struct commit *); 
-
-int sort_list_in_merge_order(struct commit_list *list, emitter_func emitter);
-
-/* Low bits are used by rev-list */
-#define UNINTERESTING   (1u<<10)
-#define BOUNDARY        (1u<<11)
-#define VISITED         (1u<<12)
-#define DISCONTINUITY   (1u<<13)
-#define LAST_EPOCH_FLAG (1u<<14)
-
-
-#endif	/* EPOCH_H */
diff --git a/git-archimport.perl b/git-archimport.perl
index 6792624d46..740bc1fd52 100755
--- a/git-archimport.perl
+++ b/git-archimport.perl
@@ -928,7 +928,7 @@ sub find_parents {
 
 	# now walk up to the mergepoint collecting what patches we have
 	my $branchtip = git_rev_parse($ps->{branch});
-	my @ancestors = `git-rev-list --merge-order $branchtip ^$mergebase`;
+	my @ancestors = `git-rev-list --topo-order $branchtip ^$mergebase`;
 	my %have; # collected merges this branch has
 	foreach my $merge (@{$ps->{merges}}) {
 	    $have{$merge} = 1;
@@ -951,7 +951,7 @@ sub find_parents {
 	# see what the remote branch has - these are the merges we 
 	# will want to have in a consecutive series from the mergebase
 	my $otherbranchtip = git_rev_parse($branch);
-	my @needraw = `git-rev-list --merge-order $otherbranchtip ^$mergebase`;
+	my @needraw = `git-rev-list --topo-order $otherbranchtip ^$mergebase`;
 	my @need;
 	foreach my $needps (@needraw) { 	# get the psets
 	    $needps = commitid2pset($needps);
diff --git a/git.c b/git.c
index 993cd0d490..a547dbd913 100644
--- a/git.c
+++ b/git.c
@@ -12,6 +12,10 @@
 #include "git-compat-util.h"
 #include "exec_cmd.h"
 
+#include "cache.h"
+#include "commit.h"
+#include "revision.h"
+
 #ifndef PATH_MAX
 # define PATH_MAX 4096
 #endif
@@ -245,6 +249,80 @@ static int cmd_help(int argc, char **argv, char **envp)
 	return 0;
 }
 
+#define LOGSIZE (65536)
+
+static int cmd_log(int argc, char **argv, char **envp)
+{
+	struct rev_info rev;
+	struct commit *commit;
+	char *buf = xmalloc(LOGSIZE);
+	static enum cmit_fmt commit_format = CMIT_FMT_DEFAULT;
+	int abbrev = DEFAULT_ABBREV;
+	int show_parents = 0;
+	const char *commit_prefix = "commit ";
+
+	argc = setup_revisions(argc, argv, &rev, "HEAD");
+	while (1 < argc) {
+		char *arg = argv[1];
+		if (!strncmp(arg, "--pretty", 8)) {
+			commit_format = get_commit_format(arg + 8);
+			if (commit_format == CMIT_FMT_ONELINE)
+				commit_prefix = "";
+		}
+		else if (!strcmp(arg, "--parents")) {
+			show_parents = 1;
+		}
+		else if (!strcmp(arg, "--no-abbrev")) {
+			abbrev = 0;
+		}
+		else if (!strncmp(arg, "--abbrev=", 9)) {
+			abbrev = strtoul(arg + 9, NULL, 10);
+			if (abbrev && abbrev < MINIMUM_ABBREV)
+				abbrev = MINIMUM_ABBREV;
+			else if (40 < abbrev)
+				abbrev = 40;
+		}
+		else
+			die("unrecognized argument: %s", arg);
+		argc--; argv++;
+	}
+
+	prepare_revision_walk(&rev);
+	setup_pager();
+	while ((commit = get_revision(&rev)) != NULL) {
+		printf("%s%s", commit_prefix,
+		       sha1_to_hex(commit->object.sha1));
+		if (show_parents) {
+			struct commit_list *parents = commit->parents;
+			while (parents) {
+				struct object *o = &(parents->item->object);
+				parents = parents->next;
+				if (o->flags & TMP_MARK)
+					continue;
+				printf(" %s", sha1_to_hex(o->sha1));
+				o->flags |= TMP_MARK;
+			}
+			/* TMP_MARK is a general purpose flag that can
+			 * be used locally, but the user should clean
+			 * things up after it is done with them.
+			 */
+			for (parents = commit->parents;
+			     parents;
+			     parents = parents->next)
+				parents->item->object.flags &= ~TMP_MARK;
+		}
+		if (commit_format == CMIT_FMT_ONELINE)
+			putchar(' ');
+		else
+			putchar('\n');
+		pretty_print_commit(commit_format, commit, ~0, buf,
+				    LOGSIZE, abbrev);
+		printf("%s\n", buf);
+	}
+	free(buf);
+	return 0;
+}
+
 #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
 
 static void handle_internal_command(int argc, char **argv, char **envp)
@@ -256,6 +334,7 @@ static void handle_internal_command(int argc, char **argv, char **envp)
 	} commands[] = {
 		{ "version", cmd_version },
 		{ "help", cmd_help },
+		{ "log", cmd_log },
 	};
 	int i;
 
diff --git a/pager.c b/pager.c
new file mode 100644
index 0000000000..1364e15d23
--- /dev/null
+++ b/pager.c
@@ -0,0 +1,48 @@
+#include "cache.h"
+
+/*
+ * This is split up from the rest of git so that we might do
+ * something different on Windows, for example.
+ */
+
+static void run_pager(void)
+{
+	const char *prog = getenv("PAGER");
+	if (!prog)
+		prog = "less";
+	setenv("LESS", "-S", 0);
+	execlp(prog, prog, NULL);
+}
+
+void setup_pager(void)
+{
+	pid_t pid;
+	int fd[2];
+
+	if (!isatty(1))
+		return;
+	if (pipe(fd) < 0)
+		return;
+	pid = fork();
+	if (pid < 0) {
+		close(fd[0]);
+		close(fd[1]);
+		return;
+	}
+
+	/* return in the child */
+	if (!pid) {
+		dup2(fd[1], 1);
+		close(fd[0]);
+		close(fd[1]);
+		return;
+	}
+
+	/* The original process turns into the PAGER */
+	dup2(fd[0], 0);
+	close(fd[0]);
+	close(fd[1]);
+
+	run_pager();
+	exit(255);
+}
diff --git a/rev-list.c b/rev-list.c
index 67d2a483fc..8e4d83efba 100644
--- a/rev-list.c
+++ b/rev-list.c
@@ -4,15 +4,12 @@
 #include "commit.h"
 #include "tree.h"
 #include "blob.h"
-#include "epoch.h"
 #include "diff.h"
+#include "revision.h"
 
-#define SEEN		(1u << 0)
-#define INTERESTING	(1u << 1)
-#define COUNTED		(1u << 2)
-#define SHOWN		(1u << 3)
-#define TREECHANGE	(1u << 4)
-#define TMP_MARK	(1u << 5) /* for isolated cases; clean after use */
+/* bits #0-4 in revision.h */
+
+#define COUNTED		(1u<<5)
 
 static const char rev_list_usage[] =
 "git-rev-list [OPTION] <commit-id>... [ -- paths... ]\n"
@@ -25,7 +22,6 @@ static const char rev_list_usage[] =
 "    --remove-empty\n"
 "    --all\n"
 "  ordering output:\n"
-"    --merge-order [ --show-breaks ]\n"
 "    --topo-order\n"
 "    --date-order\n"
 "  formatting output:\n"
@@ -38,72 +34,18 @@ static const char rev_list_usage[] =
 "    --bisect"
 ;
 
-static int dense = 1;
-static int unpacked = 0;
+struct rev_info revs;
+
 static int bisect_list = 0;
-static int tag_objects = 0;
-static int tree_objects = 0;
-static int blob_objects = 0;
-static int edge_hint = 0;
 static int verbose_header = 0;
 static int abbrev = DEFAULT_ABBREV;
 static int show_parents = 0;
 static int hdr_termination = 0;
 static const char *commit_prefix = "";
-static unsigned long max_age = -1;
-static unsigned long min_age = -1;
-static int max_count = -1;
 static enum cmit_fmt commit_format = CMIT_FMT_RAW;
-static int merge_order = 0;
-static int show_breaks = 0;
-static int stop_traversal = 0;
-static int topo_order = 0;
-static int lifo = 1;
-static int no_merges = 0;
-static const char **paths = NULL;
-static int remove_empty_trees = 0;
-
-struct name_path {
-	struct name_path *up;
-	int elem_len;
-	const char *elem;
-};
-
-static char *path_name(struct name_path *path, const char *name)
-{
-	struct name_path *p;
-	char *n, *m;
-	int nlen = strlen(name);
-	int len = nlen + 1;
-
-	for (p = path; p; p = p->up) {
-		if (p->elem_len)
-			len += p->elem_len + 1;
-	}
-	n = xmalloc(len);
-	m = n + len - (nlen + 1);
-	strcpy(m, name);
-	for (p = path; p; p = p->up) {
-		if (p->elem_len) {
-			m -= p->elem_len + 1;
-			memcpy(m, p->elem, p->elem_len);
-			m[p->elem_len] = '/';
-		}
-	}
-	return n;
-}
 
 static void show_commit(struct commit *commit)
 {
-	commit->object.flags |= SHOWN;
-	if (show_breaks) {
-		commit_prefix = "| ";
-		if (commit->object.flags & DISCONTINUITY) {
-			commit_prefix = "^ ";     
-		} else if (commit->object.flags & BOUNDARY) {
-			commit_prefix = "= ";
-		} 
-        }        		
 	printf("%s%s", commit_prefix, sha1_to_hex(commit->object.sha1));
 	if (show_parents) {
 		struct commit_list *parents = commit->parents;
@@ -137,86 +79,6 @@ static void show_commit(struct commit *commit)
 	fflush(stdout);
 }
 
-static int rewrite_one(struct commit **pp)
-{
-	for (;;) {
-		struct commit *p = *pp;
-		if (p->object.flags & (TREECHANGE | UNINTERESTING))
-			return 0;
-		if (!p->parents)
-			return -1;
-		*pp = p->parents->item;
-	}
-}
-
-static void rewrite_parents(struct commit *commit)
-{
-	struct commit_list **pp = &commit->parents;
-	while (*pp) {
-		struct commit_list *parent = *pp;
-		if (rewrite_one(&parent->item) < 0) {
-			*pp = parent->next;
-			continue;
-		}
-		pp = &parent->next;
-	}
-}
-
-static int filter_commit(struct commit * commit)
-{
-	if (stop_traversal && (commit->object.flags & BOUNDARY))
-		return STOP;
-	if (commit->object.flags & (UNINTERESTING|SHOWN))
-		return CONTINUE;
-	if (min_age != -1 && (commit->date > min_age))
-		return CONTINUE;
-	if (max_age != -1 && (commit->date < max_age)) {
-		stop_traversal=1;
-		return CONTINUE;
-	}
-	if (no_merges && (commit->parents && commit->parents->next))
-		return CONTINUE;
-	if (paths && dense) {
-		if (!(commit->object.flags & TREECHANGE))
-			return CONTINUE;
-		rewrite_parents(commit);
-	}
-	return DO;
-}
-
-static int process_commit(struct commit * commit)
-{
-	int action=filter_commit(commit);
-
-	if (action == STOP) {
-		return STOP;
-	}
-
-	if (action == CONTINUE) {
-		return CONTINUE;
-	}
-
-	if (max_count != -1 && !max_count--)
-		return STOP;
-
-	show_commit(commit);
-
-	return CONTINUE;
-}
-
-static struct object_list **add_object(struct object *obj,
-				       struct object_list **p,
-				       struct name_path *path,
-				       const char *name)
-{
-	struct object_list *entry = xmalloc(sizeof(*entry));
-	entry->item = obj;
-	entry->next = *p;
-	entry->name = path_name(path, name);
-	*p = entry;
-	return &entry->next;
-}
-
 static struct object_list **process_blob(struct blob *blob,
 					 struct object_list **p,
 					 struct name_path *path,
@@ -224,7 +86,7 @@ static struct object_list **process_blob(struct blob *blob,
 {
 	struct object *obj = &blob->object;
 
-	if (!blob_objects)
+	if (!revs.blob_objects)
 		return p;
 	if (obj->flags & (UNINTERESTING | SEEN))
 		return p;
@@ -241,7 +103,7 @@ static struct object_list **process_tree(struct tree *tree,
 	struct tree_entry_list *entry;
 	struct name_path me;
 
-	if (!tree_objects)
+	if (!revs.tree_objects)
 		return p;
 	if (obj->flags & (UNINTERESTING | SEEN))
 		return p;
@@ -266,19 +128,16 @@ static struct object_list **process_tree(struct tree *tree,
 	return p;
 }
 
-static struct object_list *pending_objects = NULL;
-
-static void show_commit_list(struct commit_list *list)
+static void show_commit_list(struct rev_info *revs)
 {
+	struct commit *commit;
 	struct object_list *objects = NULL, **p = &objects, *pending;
-	while (list) {
-		struct commit *commit = pop_most_recent_commit(&list, SEEN);
 
+	while ((commit = get_revision(revs)) != NULL) {
 		p = process_tree(commit->tree, p, NULL, "");
-		if (process_commit(commit) == STOP)
-			break;
+		show_commit(commit);
 	}
-	for (pending = pending_objects; pending; pending = pending->next) {
+	for (pending = revs->pending_objects; pending; pending = pending->next) {
 		struct object *obj = pending->item;
 		const char *name = pending->name;
 		if (obj->flags & (UNINTERESTING | SEEN))
@@ -314,88 +173,6 @@ static void show_commit_list(struct commit_list *list)
 	}
 }
 
-static void mark_blob_uninteresting(struct blob *blob)
-{
-	if (!blob_objects)
-		return;
-	if (blob->object.flags & UNINTERESTING)
-		return;
-	blob->object.flags |= UNINTERESTING;
-}
-
-static void mark_tree_uninteresting(struct tree *tree)
-{
-	struct object *obj = &tree->object;
-	struct tree_entry_list *entry;
-
-	if (!tree_objects)
-		return;
-	if (obj->flags & UNINTERESTING)
-		return;
-	obj->flags |= UNINTERESTING;
-	if (!has_sha1_file(obj->sha1))
-		return;
-	if (parse_tree(tree) < 0)
-		die("bad tree %s", sha1_to_hex(obj->sha1));
-	entry = tree->entries;
-	tree->entries = NULL;
-	while (entry) {
-		struct tree_entry_list *next = entry->next;
-		if (entry->directory)
-			mark_tree_uninteresting(entry->item.tree);
-		else
-			mark_blob_uninteresting(entry->item.blob);
-		free(entry);
-		entry = next;
-	}
-}
-
-static void mark_parents_uninteresting(struct commit *commit)
-{
-	struct commit_list *parents = commit->parents;
-
-	while (parents) {
-		struct commit *commit = parents->item;
-		commit->object.flags |= UNINTERESTING;
-
-		/*
-		 * Normally we haven't parsed the parent
-		 * yet, so we won't have a parent of a parent
-		 * here. However, it may turn out that we've
-		 * reached this commit some other way (where it
-		 * wasn't uninteresting), in which case we need
-		 * to mark its parents recursively too..
-		 */
-		if (commit->parents)
-			mark_parents_uninteresting(commit);
-
-		/*
-		 * A missing commit is ok iff its parent is marked 
-		 * uninteresting.
-		 *
-		 * We just mark such a thing parsed, so that when
-		 * it is popped next time around, we won't be trying
-		 * to parse it and get an error.
-		 */
-		if (!has_sha1_file(commit->object.sha1))
-			commit->object.parsed = 1;
-		parents = parents->next;
-	}
-}
-
-static int everybody_uninteresting(struct commit_list *orig)
-{
-	struct commit_list *list = orig;
-	while (list) {
-		struct commit *commit = list->item;
-		list = list->next;
-		if (commit->object.flags & UNINTERESTING)
-			continue;
-		return 0;
-	}
-	return 1;
-}
-
 /*
  * This is a truly stupid algorithm, but it's only
  * used for bisection, and we just don't care enough.
@@ -413,7 +190,7 @@ static int count_distance(struct commit_list *entry)
 
 		if (commit->object.flags & (UNINTERESTING | COUNTED))
 			break;
-		if (!paths || (commit->object.flags & TREECHANGE))
+		if (!revs.paths || (commit->object.flags & TREECHANGE))
 			nr++;
 		commit->object.flags |= COUNTED;
 		p = commit->parents;
@@ -447,7 +224,7 @@ static struct commit_list *find_bisection(struct commit_list *list)
 	nr = 0;
 	p = list;
 	while (p) {
-		if (!paths || (p->item->object.flags & TREECHANGE))
+		if (!revs.paths || (p->item->object.flags & TREECHANGE))
 			nr++;
 		p = p->next;
 	}
@@ -457,7 +234,7 @@ static struct commit_list *find_bisection(struct commit_list *list)
 	for (p = list; p; p = p->next) {
 		int distance;
 
-		if (paths && !(p->item->object.flags & TREECHANGE))
+		if (revs.paths && !(p->item->object.flags & TREECHANGE))
 			continue;
 
 		distance = count_distance(p);
@@ -483,7 +260,7 @@ static void mark_edge_parents_uninteresting(struct commit *commit)
 		if (!(parent->object.flags & UNINTERESTING))
 			continue;
 		mark_tree_uninteresting(parent->tree);
-		if (edge_hint && !(parent->object.flags & SHOWN)) {
+		if (revs.edge_hint && !(parent->object.flags & SHOWN)) {
 			parent->object.flags |= SHOWN;
 			printf("-%s\n", sha1_to_hex(parent->object.sha1));
 		}
@@ -503,356 +280,29 @@ static void mark_edges_uninteresting(struct commit_list *list)
 	}
 }
 
-#define TREE_SAME	0
-#define TREE_NEW	1
-#define TREE_DIFFERENT	2
-static int tree_difference = TREE_SAME;
-
-static void file_add_remove(struct diff_options *options,
-		    int addremove, unsigned mode,
-		    const unsigned char *sha1,
-		    const char *base, const char *path)
-{
-	int diff = TREE_DIFFERENT;
-
-	/*
-	 * Is it an add of a new file? It means that
-	 * the old tree didn't have it at all, so we
-	 * will turn "TREE_SAME" -> "TREE_NEW", but
-	 * leave any "TREE_DIFFERENT" alone (and if
-	 * it already was "TREE_NEW", we'll keep it
-	 * "TREE_NEW" of course).
-	 */
-	if (addremove == '+') {
-		diff = tree_difference;
-		if (diff != TREE_SAME)
-			return;
-		diff = TREE_NEW;
-	}
-	tree_difference = diff;
-}
-
-static void file_change(struct diff_options *options,
-		 unsigned old_mode, unsigned new_mode,
-		 const unsigned char *old_sha1,
-		 const unsigned char *new_sha1,
-		 const char *base, const char *path)
-{
-	tree_difference = TREE_DIFFERENT;
-}
-
-static struct diff_options diff_opt = {
-	.recursive = 1,
-	.add_remove = file_add_remove,
-	.change = file_change,
-};
-
-static int compare_tree(struct tree *t1, struct tree *t2)
-{
-	if (!t1)
-		return TREE_NEW;
-	if (!t2)
-		return TREE_DIFFERENT;
-	tree_difference = TREE_SAME;
-	if (diff_tree_sha1(t1->object.sha1, t2->object.sha1, "", &diff_opt) < 0)
-		return TREE_DIFFERENT;
-	return tree_difference;
-}
-
-static int same_tree_as_empty(struct tree *t1)
-{
-	int retval;
-	void *tree;
-	struct tree_desc empty, real;
-
-	if (!t1)
-		return 0;
-
-	tree = read_object_with_reference(t1->object.sha1, "tree", &real.size, NULL);
-	if (!tree)
-		return 0;
-	real.buf = tree;
-
-	empty.buf = "";
-	empty.size = 0;
-
-	tree_difference = 0;
-	retval = diff_tree(&empty, &real, "", &diff_opt);
-	free(tree);
-
-	return retval >= 0 && !tree_difference;
-}
-
-static void try_to_simplify_commit(struct commit *commit)
-{
-	struct commit_list **pp, *parent;
-
-	if (!commit->tree)
-		return;
-
-	if (!commit->parents) {
-		if (!same_tree_as_empty(commit->tree))
-			commit->object.flags |= TREECHANGE;
-		return;
-	}
-
-	pp = &commit->parents;
-	while ((parent = *pp) != NULL) {
-		struct commit *p = parent->item;
-
-		if (p->object.flags & UNINTERESTING) {
-			pp = &parent->next;
-			continue;
-		}
-
-		parse_commit(p);
-		switch (compare_tree(p->tree, commit->tree)) {
-		case TREE_SAME:
-			parent->next = NULL;
-			commit->parents = parent;
-			return;
-
-		case TREE_NEW:
-			if (remove_empty_trees && same_tree_as_empty(p->tree)) {
-				*pp = parent->next;
-				continue;
-			}
-		/* fallthrough */
-		case TREE_DIFFERENT:
-			pp = &parent->next;
-			continue;
-		}
-		die("bad tree compare for commit %s", sha1_to_hex(commit->object.sha1));
-	}
-	commit->object.flags |= TREECHANGE;
-}
-
-static void add_parents_to_list(struct commit *commit, struct commit_list **list)
-{
-	struct commit_list *parent = commit->parents;
-
-	/*
-	 * If the commit is uninteresting, don't try to
-	 * prune parents - we want the maximal uninteresting
-	 * set.
-	 *
-	 * Normally we haven't parsed the parent
-	 * yet, so we won't have a parent of a parent
-	 * here. However, it may turn out that we've
-	 * reached this commit some other way (where it
-	 * wasn't uninteresting), in which case we need
-	 * to mark its parents recursively too..
-	 */
-	if (commit->object.flags & UNINTERESTING) {
-		while (parent) {
-			struct commit *p = parent->item;
-			parent = parent->next;
-			parse_commit(p);
-			p->object.flags |= UNINTERESTING;
-			if (p->parents)
-				mark_parents_uninteresting(p);
-			if (p->object.flags & SEEN)
-				continue;
-			p->object.flags |= SEEN;
-			insert_by_date(p, list);
-		}
-		return;
-	}
-
-	/*
-	 * Ok, the commit wasn't uninteresting. Try to
-	 * simplify the commit history and find the parent
-	 * that has no differences in the path set if one exists.
-	 */
-	if (paths)
-		try_to_simplify_commit(commit);
-
-	parent = commit->parents;
-	while (parent) {
-		struct commit *p = parent->item;
-
-		parent = parent->next;
-
-		parse_commit(p);
-		if (p->object.flags & SEEN)
-			continue;
-		p->object.flags |= SEEN;
-		insert_by_date(p, list);
-	}
-}
-
-static struct commit_list *limit_list(struct commit_list *list)
-{
-	struct commit_list *newlist = NULL;
-	struct commit_list **p = &newlist;
-	while (list) {
-		struct commit_list *entry = list;
-		struct commit *commit = list->item;
-		struct object *obj = &commit->object;
-
-		list = list->next;
-		free(entry);
-
-		if (max_age != -1 && (commit->date < max_age))
-			obj->flags |= UNINTERESTING;
-		if (unpacked && has_sha1_pack(obj->sha1))
-			obj->flags |= UNINTERESTING;
-		add_parents_to_list(commit, &list);
-		if (obj->flags & UNINTERESTING) {
-			mark_parents_uninteresting(commit);
-			if (everybody_uninteresting(list))
-				break;
-			continue;
-		}
-		if (min_age != -1 && (commit->date > min_age))
-			continue;
-		p = &commit_list_insert(commit, p)->next;
-	}
-	if (tree_objects)
-		mark_edges_uninteresting(newlist);
-	if (bisect_list)
-		newlist = find_bisection(newlist);
-	return newlist;
-}
-
-static void add_pending_object(struct object *obj, const char *name)
-{
-	add_object(obj, &pending_objects, NULL, name);
-}
-
-static struct commit *get_commit_reference(const char *name, const unsigned char *sha1, unsigned int flags)
-{
-	struct object *object;
-
-	object = parse_object(sha1);
-	if (!object)
-		die("bad object %s", name);
-
-	/*
-	 * Tag object? Look what it points to..
-	 */
-	while (object->type == tag_type) {
-		struct tag *tag = (struct tag *) object;
-		object->flags |= flags;
-		if (tag_objects && !(object->flags & UNINTERESTING))
-			add_pending_object(object, tag->tag);
-		object = parse_object(tag->tagged->sha1);
-		if (!object)
-			die("bad object %s", sha1_to_hex(tag->tagged->sha1));
-	}
-
-	/*
-	 * Commit object? Just return it, we'll do all the complex
-	 * reachability crud.
-	 */
-	if (object->type == commit_type) {
-		struct commit *commit = (struct commit *)object;
-		object->flags |= flags;
-		if (parse_commit(commit) < 0)
-			die("unable to parse commit %s", name);
-		if (flags & UNINTERESTING)
-			mark_parents_uninteresting(commit);
-		return commit;
-	}
-
-	/*
-	 * Tree object? Either mark it uniniteresting, or add it
-	 * to the list of objects to look at later..
-	 */
-	if (object->type == tree_type) {
-		struct tree *tree = (struct tree *)object;
-		if (!tree_objects)
-			return NULL;
-		if (flags & UNINTERESTING) {
-			mark_tree_uninteresting(tree);
-			return NULL;
-		}
-		add_pending_object(object, "");
-		return NULL;
-	}
-
-	/*
-	 * Blob object? You know the drill by now..
-	 */
-	if (object->type == blob_type) {
-		struct blob *blob = (struct blob *)object;
-		if (!blob_objects)
-			return NULL;
-		if (flags & UNINTERESTING) {
-			mark_blob_uninteresting(blob);
-			return NULL;
-		}
-		add_pending_object(object, "");
-		return NULL;
-	}
-	die("%s is unknown object", name);
-}
-
-static void handle_one_commit(struct commit *com, struct commit_list **lst)
-{
-	if (!com || com->object.flags & SEEN)
-		return;
-	com->object.flags |= SEEN;
-	commit_list_insert(com, lst);
-}
-
-/* for_each_ref() callback does not allow user data -- Yuck. */
-static struct commit_list **global_lst;
-
-static int include_one_commit(const char *path, const unsigned char *sha1)
-{
-	struct commit *com = get_commit_reference(path, sha1, 0);
-	handle_one_commit(com, global_lst);
-	return 0;
-}
-
-static void handle_all(struct commit_list **lst)
-{
-	global_lst = lst;
-	for_each_ref(include_one_commit);
-	global_lst = NULL;
-}
-
 int main(int argc, const char **argv)
 {
-	const char *prefix = setup_git_directory();
-	struct commit_list *list = NULL;
-	int i, limited = 0;
+	struct commit_list *list;
+	int i;
+
+	argc = setup_revisions(argc, argv, &revs, NULL);
 
 	for (i = 1 ; i < argc; i++) {
-		int flags;
 		const char *arg = argv[i];
-		char *dotdot;
-		struct commit *commit;
-		unsigned char sha1[20];
 
 		/* accept -<digit>, like traditilnal "head" */
 		if ((*arg == '-') && isdigit(arg[1])) {
-			max_count = atoi(arg + 1);
+			revs.max_count = atoi(arg + 1);
 			continue;
 		}
 		if (!strcmp(arg, "-n")) {
 			if (++i >= argc)
 				die("-n requires an argument");
-			max_count = atoi(argv[i]);
+			revs.max_count = atoi(argv[i]);
 			continue;
 		}
 		if (!strncmp(arg,"-n",2)) {
-			max_count = atoi(arg + 2);
-			continue;
-		}
-		if (!strncmp(arg, "--max-count=", 12)) {
-			max_count = atoi(arg + 12);
-			continue;
-		}
-		if (!strncmp(arg, "--max-age=", 10)) {
-			max_age = atoi(arg + 10);
-			limited = 1;
-			continue;
-		}
-		if (!strncmp(arg, "--min-age=", 10)) {
-			min_age = atoi(arg + 10);
-			limited = 1;
+			revs.max_count = atoi(arg + 2);
 			continue;
 		}
 		if (!strcmp(arg, "--header")) {
@@ -881,10 +331,6 @@ int main(int argc, const char **argv)
 				commit_prefix = "commit ";
 			continue;
 		}
-		if (!strncmp(arg, "--no-merges", 11)) {
-			no_merges = 1;
-			continue;
-		}
 		if (!strcmp(arg, "--parents")) {
 			show_parents = 1;
 			continue;
@@ -893,140 +339,27 @@ int main(int argc, const char **argv)
 			bisect_list = 1;
 			continue;
 		}
-		if (!strcmp(arg, "--all")) {
-			handle_all(&list);
-			continue;
-		}
-		if (!strcmp(arg, "--objects")) {
-			tag_objects = 1;
-			tree_objects = 1;
-			blob_objects = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--objects-edge")) {
-			tag_objects = 1;
-			tree_objects = 1;
-			blob_objects = 1;
-			edge_hint = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--unpacked")) {
-			unpacked = 1;
-			limited = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--merge-order")) {
-		        merge_order = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--show-breaks")) {
-			show_breaks = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--topo-order")) {
-		        topo_order = 1;
-			lifo = 1;
-		        limited = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--date-order")) {
-		        topo_order = 1;
-			lifo = 0;
-		        limited = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--dense")) {
-			dense = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--sparse")) {
-			dense = 0;
-			continue;
-		}
-		if (!strcmp(arg, "--remove-empty")) {
-			remove_empty_trees = 1;
-			continue;
-		}
-		if (!strcmp(arg, "--")) {
-			i++;
-			break;
-		}
-
-		if (show_breaks && !merge_order)
-			usage(rev_list_usage);
+		usage(rev_list_usage);
 
-		flags = 0;
-		dotdot = strstr(arg, "..");
-		if (dotdot) {
-			unsigned char from_sha1[20];
-			char *next = dotdot + 2;
-			*dotdot = 0;
-			if (!*next)
-				next = "HEAD";
-			if (!get_sha1(arg, from_sha1) && !get_sha1(next, sha1)) {
-				struct commit *exclude;
-				struct commit *include;
-				
-				exclude = get_commit_reference(arg, from_sha1, UNINTERESTING);
-				include = get_commit_reference(next, sha1, 0);
-				if (!exclude || !include)
-					die("Invalid revision range %s..%s", arg, next);
-				limited = 1;
-				handle_one_commit(exclude, &list);
-				handle_one_commit(include, &list);
-				continue;
-			}
-			*dotdot = '.';
-		}
-		if (*arg == '^') {
-			flags = UNINTERESTING;
-			arg++;
-			limited = 1;
-		}
-		if (get_sha1(arg, sha1) < 0) {
-			struct stat st;
-			if (lstat(arg, &st) < 0)
-				die("'%s': %s", arg, strerror(errno));
-			break;
-		}
-		commit = get_commit_reference(arg, sha1, flags);
-		handle_one_commit(commit, &list);
 	}
 
+	list = revs.commits;
+
 	if (!list &&
-	    (!(tag_objects||tree_objects||blob_objects) && !pending_objects))
+	    (!(revs.tag_objects||revs.tree_objects||revs.blob_objects) && !revs.pending_objects))
 		usage(rev_list_usage);
 
-	paths = get_pathspec(prefix, argv + i);
-	if (paths) {
-		limited = 1;
-		diff_tree_setup_paths(paths);
-	}
+	prepare_revision_walk(&revs);
+	if (revs.tree_objects)
+		mark_edges_uninteresting(revs.commits);
+
+	if (bisect_list)
+		revs.commits = find_bisection(revs.commits);
 
 	save_commit_buffer = verbose_header;
 	track_object_refs = 0;
 
-	if (!merge_order) {		
-		sort_by_date(&list);
-		if (list && !limited && max_count == 1 &&
-		    !tag_objects && !tree_objects && !blob_objects) {
-			show_commit(list->item);
-			return 0;
-		}
-	        if (limited)
-			list = limit_list(list);
-		if (topo_order)
-			sort_in_topological_order(&list, lifo);
-		show_commit_list(list);
-	} else {
-#ifndef NO_OPENSSL
-		if (sort_list_in_merge_order(list, &process_commit)) {
-			die("merge order sort failed\n");
-		}
-#else
-		die("merge order sort unsupported, OpenSSL not linked");
-#endif
-	}
+	show_commit_list(&revs);
 
 	return 0;
 }
diff --git a/rev-parse.c b/rev-parse.c
index 610eacb35a..f90e999e60 100644
--- a/rev-parse.c
+++ b/rev-parse.c
@@ -39,14 +39,12 @@ static int is_rev_argument(const char *arg)
 		"--header",
 		"--max-age=",
 		"--max-count=",
-		"--merge-order",
 		"--min-age=",
 		"--no-merges",
 		"--objects",
 		"--objects-edge",
 		"--parents",
 		"--pretty",
-		"--show-breaks",
 		"--sparse",
 		"--topo-order",
 		"--date-order",
diff --git a/revision.c b/revision.c
new file mode 100644
index 0000000000..a3df810076
--- /dev/null
+++ b/revision.c
@@ -0,0 +1,722 @@
+#include "cache.h"
+#include "tag.h"
+#include "blob.h"
+#include "tree.h"
+#include "commit.h"
+#include "diff.h"
+#include "refs.h"
+#include "revision.h"
+
+static char *path_name(struct name_path *path, const char *name)
+{
+	struct name_path *p;
+	char *n, *m;
+	int nlen = strlen(name);
+	int len = nlen + 1;
+
+	for (p = path; p; p = p->up) {
+		if (p->elem_len)
+			len += p->elem_len + 1;
+	}
+	n = xmalloc(len);
+	m = n + len - (nlen + 1);
+	strcpy(m, name);
+	for (p = path; p; p = p->up) {
+		if (p->elem_len) {
+			m -= p->elem_len + 1;
+			memcpy(m, p->elem, p->elem_len);
+			m[p->elem_len] = '/';
+		}
+	}
+	return n;
+}
+
+struct object_list **add_object(struct object *obj,
+				       struct object_list **p,
+				       struct name_path *path,
+				       const char *name)
+{
+	struct object_list *entry = xmalloc(sizeof(*entry));
+	entry->item = obj;
+	entry->next = *p;
+	entry->name = path_name(path, name);
+	*p = entry;
+	return &entry->next;
+}
+
+static void mark_blob_uninteresting(struct blob *blob)
+{
+	if (blob->object.flags & UNINTERESTING)
+		return;
+	blob->object.flags |= UNINTERESTING;
+}
+
+void mark_tree_uninteresting(struct tree *tree)
+{
+	struct object *obj = &tree->object;
+	struct tree_entry_list *entry;
+
+	if (obj->flags & UNINTERESTING)
+		return;
+	obj->flags |= UNINTERESTING;
+	if (!has_sha1_file(obj->sha1))
+		return;
+	if (parse_tree(tree) < 0)
+		die("bad tree %s", sha1_to_hex(obj->sha1));
+	entry = tree->entries;
+	tree->entries = NULL;
+	while (entry) {
+		struct tree_entry_list *next = entry->next;
+		if (entry->directory)
+			mark_tree_uninteresting(entry->item.tree);
+		else
+			mark_blob_uninteresting(entry->item.blob);
+		free(entry);
+		entry = next;
+	}
+}
+
+void mark_parents_uninteresting(struct commit *commit)
+{
+	struct commit_list *parents = commit->parents;
+
+	while (parents) {
+		struct commit *commit = parents->item;
+		commit->object.flags |= UNINTERESTING;
+
+		/*
+		 * Normally we haven't parsed the parent
+		 * yet, so we won't have a parent of a parent
+		 * here. However, it may turn out that we've
+		 * reached this commit some other way (where it
+		 * wasn't uninteresting), in which case we need
+		 * to mark its parents recursively too..
+		 */
+		if (commit->parents)
+			mark_parents_uninteresting(commit);
+
+		/*
+		 * A missing commit is ok iff its parent is marked
+		 * uninteresting.
+		 *
+		 * We just mark such a thing parsed, so that when
+		 * it is popped next time around, we won't be trying
+		 * to parse it and get an error.
+		 */
+		if (!has_sha1_file(commit->object.sha1))
+			commit->object.parsed = 1;
+		parents = parents->next;
+	}
+}
+
+static void add_pending_object(struct rev_info *revs, struct object *obj, const char *name)
+{
+	add_object(obj, &revs->pending_objects, NULL, name);
+}
+
+static struct commit *get_commit_reference(struct rev_info *revs, const char *name, const unsigned char *sha1, unsigned int flags)
+{
+	struct object *object;
+
+	object = parse_object(sha1);
+	if (!object)
+		die("bad object %s", name);
+
+	/*
+	 * Tag object? Look what it points to..
+	 */
+	while (object->type == tag_type) {
+		struct tag *tag = (struct tag *) object;
+		object->flags |= flags;
+		if (revs->tag_objects && !(object->flags & UNINTERESTING))
+			add_pending_object(revs, object, tag->tag);
+		object = parse_object(tag->tagged->sha1);
+		if (!object)
+			die("bad object %s", sha1_to_hex(tag->tagged->sha1));
+	}
+
+	/*
+	 * Commit object? Just return it, we'll do all the complex
+	 * reachability crud.
+	 */
+	if (object->type == commit_type) {
+		struct commit *commit = (struct commit *)object;
+		object->flags |= flags;
+		if (parse_commit(commit) < 0)
+			die("unable to parse commit %s", name);
+		if (flags & UNINTERESTING) {
+			mark_parents_uninteresting(commit);
+			revs->limited = 1;
+		}
+		return commit;
+	}
+
+	/*
+	 * Tree object? Either mark it uniniteresting, or add it
+	 * to the list of objects to look at later..
+	 */
+	if (object->type == tree_type) {
+		struct tree *tree = (struct tree *)object;
+		if (!revs->tree_objects)
+			return NULL;
+		if (flags & UNINTERESTING) {
+			mark_tree_uninteresting(tree);
+			return NULL;
+		}
+		add_pending_object(revs, object, "");
+		return NULL;
+	}
+
+	/*
+	 * Blob object? You know the drill by now..
+	 */
+	if (object->type == blob_type) {
+		struct blob *blob = (struct blob *)object;
+		if (!revs->blob_objects)
+			return NULL;
+		if (flags & UNINTERESTING) {
+			mark_blob_uninteresting(blob);
+			return NULL;
+		}
+		add_pending_object(revs, object, "");
+		return NULL;
+	}
+	die("%s is unknown object", name);
+}
+
+static int everybody_uninteresting(struct commit_list *orig)
+{
+	struct commit_list *list = orig;
+	while (list) {
+		struct commit *commit = list->item;
+		list = list->next;
+		if (commit->object.flags & UNINTERESTING)
+			continue;
+		return 0;
+	}
+	return 1;
+}
+
+#define TREE_SAME	0
+#define TREE_NEW	1
+#define TREE_DIFFERENT	2
+static int tree_difference = TREE_SAME;
+
+static void file_add_remove(struct diff_options *options,
+		    int addremove, unsigned mode,
+		    const unsigned char *sha1,
+		    const char *base, const char *path)
+{
+	int diff = TREE_DIFFERENT;
+
+	/*
+	 * Is it an add of a new file? It means that
+	 * the old tree didn't have it at all, so we
+	 * will turn "TREE_SAME" -> "TREE_NEW", but
+	 * leave any "TREE_DIFFERENT" alone (and if
+	 * it already was "TREE_NEW", we'll keep it
+	 * "TREE_NEW" of course).
+	 */
+	if (addremove == '+') {
+		diff = tree_difference;
+		if (diff != TREE_SAME)
+			return;
+		diff = TREE_NEW;
+	}
+	tree_difference = diff;
+}
+
+static void file_change(struct diff_options *options,
+		 unsigned old_mode, unsigned new_mode,
+		 const unsigned char *old_sha1,
+		 const unsigned char *new_sha1,
+		 const char *base, const char *path)
+{
+	tree_difference = TREE_DIFFERENT;
+}
+
+static struct diff_options diff_opt = {
+	.recursive = 1,
+	.add_remove = file_add_remove,
+	.change = file_change,
+};
+
+static int compare_tree(struct tree *t1, struct tree *t2)
+{
+	if (!t1)
+		return TREE_NEW;
+	if (!t2)
+		return TREE_DIFFERENT;
+	tree_difference = TREE_SAME;
+	if (diff_tree_sha1(t1->object.sha1, t2->object.sha1, "", &diff_opt) < 0)
+		return TREE_DIFFERENT;
+	return tree_difference;
+}
+
+static int same_tree_as_empty(struct tree *t1)
+{
+	int retval;
+	void *tree;
+	struct tree_desc empty, real;
+
+	if (!t1)
+		return 0;
+
+	tree = read_object_with_reference(t1->object.sha1, "tree", &real.size, NULL);
+	if (!tree)
+		return 0;
+	real.buf = tree;
+
+	empty.buf = "";
+	empty.size = 0;
+
+	tree_difference = 0;
+	retval = diff_tree(&empty, &real, "", &diff_opt);
+	free(tree);
+
+	return retval >= 0 && !tree_difference;
+}
+
+static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
+{
+	struct commit_list **pp, *parent;
+
+	if (!commit->tree)
+		return;
+
+	if (!commit->parents) {
+		if (!same_tree_as_empty(commit->tree))
+			commit->object.flags |= TREECHANGE;
+		return;
+	}
+
+	pp = &commit->parents;
+	while ((parent = *pp) != NULL) {
+		struct commit *p = parent->item;
+
+		if (p->object.flags & UNINTERESTING) {
+			pp = &parent->next;
+			continue;
+		}
+
+		parse_commit(p);
+		switch (compare_tree(p->tree, commit->tree)) {
+		case TREE_SAME:
+			parent->next = NULL;
+			commit->parents = parent;
+			return;
+
+		case TREE_NEW:
+			if (revs->remove_empty_trees && same_tree_as_empty(p->tree)) {
+				*pp = parent->next;
+				continue;
+			}
+		/* fallthrough */
+		case TREE_DIFFERENT:
+			pp = &parent->next;
+			continue;
+		}
+		die("bad tree compare for commit %s", sha1_to_hex(commit->object.sha1));
+	}
+	commit->object.flags |= TREECHANGE;
+}
+
+static void add_parents_to_list(struct rev_info *revs, struct commit *commit, struct commit_list **list)
+{
+	struct commit_list *parent = commit->parents;
+
+	/*
+	 * If the commit is uninteresting, don't try to
+	 * prune parents - we want the maximal uninteresting
+	 * set.
+	 *
+	 * Normally we haven't parsed the parent
+	 * yet, so we won't have a parent of a parent
+	 * here. However, it may turn out that we've
+	 * reached this commit some other way (where it
+	 * wasn't uninteresting), in which case we need
+	 * to mark its parents recursively too..
+	 */
+	if (commit->object.flags & UNINTERESTING) {
+		while (parent) {
+			struct commit *p = parent->item;
+			parent = parent->next;
+			parse_commit(p);
+			p->object.flags |= UNINTERESTING;
+			if (p->parents)
+				mark_parents_uninteresting(p);
+			if (p->object.flags & SEEN)
+				continue;
+			p->object.flags |= SEEN;
+			insert_by_date(p, list);
+		}
+		return;
+	}
+
+	/*
+	 * Ok, the commit wasn't uninteresting. Try to
+	 * simplify the commit history and find the parent
+	 * that has no differences in the path set if one exists.
+	 */
+	if (revs->paths)
+		try_to_simplify_commit(revs, commit);
+
+	parent = commit->parents;
+	while (parent) {
+		struct commit *p = parent->item;
+
+		parent = parent->next;
+
+		parse_commit(p);
+		if (p->object.flags & SEEN)
+			continue;
+		p->object.flags |= SEEN;
+		insert_by_date(p, list);
+	}
+}
+
+static void limit_list(struct rev_info *revs)
+{
+	struct commit_list *list = revs->commits;
+	struct commit_list *newlist = NULL;
+	struct commit_list **p = &newlist;
+
+	if (revs->paths)
+		diff_tree_setup_paths(revs->paths);
+
+	while (list) {
+		struct commit_list *entry = list;
+		struct commit *commit = list->item;
+		struct object *obj = &commit->object;
+
+		list = list->next;
+		free(entry);
+
+		if (revs->max_age != -1 && (commit->date < revs->max_age))
+			obj->flags |= UNINTERESTING;
+		if (revs->unpacked && has_sha1_pack(obj->sha1))
+			obj->flags |= UNINTERESTING;
+		add_parents_to_list(revs, commit, &list);
+		if (obj->flags & UNINTERESTING) {
+			mark_parents_uninteresting(commit);
+			if (everybody_uninteresting(list))
+				break;
+			continue;
+		}
+		if (revs->min_age != -1 && (commit->date > revs->min_age))
+			continue;
+		p = &commit_list_insert(commit, p)->next;
+	}
+	revs->commits = newlist;
+}
+
+static void add_one_commit(struct commit *commit, struct rev_info *revs)
+{
+	if (!commit || (commit->object.flags & SEEN))
+		return;
+	commit->object.flags |= SEEN;
+	commit_list_insert(commit, &revs->commits);
+}
+
+static int all_flags;
+static struct rev_info *all_revs;
+
+static int handle_one_ref(const char *path, const unsigned char *sha1)
+{
+	struct commit *commit = get_commit_reference(all_revs, path, sha1, all_flags);
+	add_one_commit(commit, all_revs);
+	return 0;
+}
+
+static void handle_all(struct rev_info *revs, unsigned flags)
+{
+	all_revs = revs;
+	all_flags = flags;
+	for_each_ref(handle_one_ref);
+}
+
+/*
+ * Parse revision information, filling in the "rev_info" structure,
+ * and removing the used arguments from the argument list.
+ *
+ * Returns the number of arguments left that weren't recognized
+ * (which are also moved to the head of the argument list)
+ */
+int setup_revisions(int argc, const char **argv, struct rev_info *revs, const char *def)
+{
+	int i, flags, seen_dashdash;
+	const char **unrecognized = argv + 1;
+	int left = 1;
+
+	memset(revs, 0, sizeof(*revs));
+	revs->lifo = 1;
+	revs->dense = 1;
+	revs->prefix = setup_git_directory();
+	revs->max_age = -1;
+	revs->min_age = -1;
+	revs->max_count = -1;
+
+	/* First, search for "--" */
+	seen_dashdash = 0;
+	for (i = 1; i < argc; i++) {
+		const char *arg = argv[i];
+		if (strcmp(arg, "--"))
+			continue;
+		argv[i] = NULL;
+		argc = i;
+		revs->paths = get_pathspec(revs->prefix, argv + i + 1);
+		seen_dashdash = 1;
+		break;
+	}
+
+	flags = 0;
+	for (i = 1; i < argc; i++) {
+		struct commit *commit;
+		const char *arg = argv[i];
+		unsigned char sha1[20];
+		char *dotdot;
+		int local_flags;
+
+		if (*arg == '-') {
+			if (!strncmp(arg, "--max-count=", 12)) {
+				revs->max_count = atoi(arg + 12);
+				continue;
+			}
+			/* accept -<digit>, like traditilnal "head" */
+			if ((*arg == '-') && isdigit(arg[1])) {
+				revs->max_count = atoi(arg + 1);
+				continue;
+			}
+			if (!strcmp(arg, "-n")) {
+				if (argc <= i + 1)
+					die("-n requires an argument");
+				revs->max_count = atoi(argv[++i]);
+				continue;
+			}
+			if (!strncmp(arg,"-n",2)) {
+				revs->max_count = atoi(arg + 2);
+				continue;
+			}
+			if (!strncmp(arg, "--max-age=", 10)) {
+				revs->max_age = atoi(arg + 10);
+				revs->limited = 1;
+				continue;
+			}
+			if (!strncmp(arg, "--min-age=", 10)) {
+				revs->min_age = atoi(arg + 10);
+				revs->limited = 1;
+				continue;
+			}
+			if (!strncmp(arg, "--since=", 8)) {
+				revs->max_age = approxidate(arg + 8);
+				revs->limited = 1;
+				continue;
+			}
+			if (!strncmp(arg, "--after=", 8)) {
+				revs->max_age = approxidate(arg + 8);
+				revs->limited = 1;
+				continue;
+			}
+			if (!strncmp(arg, "--before=", 9)) {
+				revs->min_age = approxidate(arg + 9);
+				revs->limited = 1;
+				continue;
+			}
+			if (!strncmp(arg, "--until=", 8)) {
+				revs->min_age = approxidate(arg + 8);
+				revs->limited = 1;
+				continue;
+			}
+			if (!strcmp(arg, "--all")) {
+				handle_all(revs, flags);
+				continue;
+			}
+			if (!strcmp(arg, "--not")) {
+				flags ^= UNINTERESTING;
+				continue;
+			}
+			if (!strcmp(arg, "--default")) {
+				if (++i >= argc)
+					die("bad --default argument");
+				def = argv[i];
+				continue;
+			}
+			if (!strcmp(arg, "--topo-order")) {
+				revs->topo_order = 1;
+				revs->limited = 1;
+				continue;
+			}
+			if (!strcmp(arg, "--date-order")) {
+				revs->lifo = 0;
+				revs->topo_order = 1;
+				revs->limited = 1;
+				continue;
+			}
+			if (!strcmp(arg, "--dense")) {
+				revs->dense = 1;
+				continue;
+			}
+			if (!strcmp(arg, "--sparse")) {
+				revs->dense = 0;
+				continue;
+			}
+			if (!strcmp(arg, "--remove-empty")) {
+				revs->remove_empty_trees = 1;
+				continue;
+			}
+			if (!strncmp(arg, "--no-merges", 11)) {
+				revs->no_merges = 1;
+				continue;
+			}
+			if (!strcmp(arg, "--objects")) {
+				revs->tag_objects = 1;
+				revs->tree_objects = 1;
+				revs->blob_objects = 1;
+				continue;
+			}
+			if (!strcmp(arg, "--objects-edge")) {
+				revs->tag_objects = 1;
+				revs->tree_objects = 1;
+				revs->blob_objects = 1;
+				revs->edge_hint = 1;
+				continue;
+			}
+			if (!strcmp(arg, "--unpacked")) {
+				revs->unpacked = 1;
+				revs->limited = 1;
+				continue;
+			}
+			*unrecognized++ = arg;
+			left++;
+			continue;
+		}
+		dotdot = strstr(arg, "..");
+		if (dotdot) {
+			unsigned char from_sha1[20];
+			char *next = dotdot + 2;
+			*dotdot = 0;
+			if (!*next)
+				next = "HEAD";
+			if (!get_sha1(arg, from_sha1) && !get_sha1(next, sha1)) {
+				struct commit *exclude;
+				struct commit *include;
+
+				exclude = get_commit_reference(revs, arg, from_sha1, flags ^ UNINTERESTING);
+				include = get_commit_reference(revs, next, sha1, flags);
+				if (!exclude || !include)
+					die("Invalid revision range %s..%s", arg, next);
+				add_one_commit(exclude, revs);
+				add_one_commit(include, revs);
+				continue;
+			}
+			*dotdot = '.';
+		}
+		local_flags = 0;
+		if (*arg == '^') {
+			local_flags = UNINTERESTING;
+			arg++;
+		}
+		if (get_sha1(arg, sha1) < 0) {
+			struct stat st;
+			int j;
+
+			if (seen_dashdash || local_flags)
+				die("bad revision '%s'", arg);
+
+			/* If we didn't have a "--", all filenames must exist */
+			for (j = i; j < argc; j++) {
+				if (lstat(argv[j], &st) < 0)
+					die("'%s': %s", arg, strerror(errno));
+			}
+			revs->paths = get_pathspec(revs->prefix, argv + i);
+			break;
+		}
+		commit = get_commit_reference(revs, arg, sha1, flags ^ local_flags);
+		add_one_commit(commit, revs);
+	}
+	if (def && !revs->commits) {
+		unsigned char sha1[20];
+		struct commit *commit;
+		if (get_sha1(def, sha1) < 0)
+			die("bad default revision '%s'", def);
+		commit = get_commit_reference(revs, def, sha1, 0);
+		add_one_commit(commit, revs);
+	}
+	if (revs->paths)
+		revs->limited = 1;
+	return left;
+}
+
+void prepare_revision_walk(struct rev_info *revs)
+{
+	sort_by_date(&revs->commits);
+	if (revs->limited)
+		limit_list(revs);
+	if (revs->topo_order)
+		sort_in_topological_order(&revs->commits, revs->lifo);
+}
+
+static int rewrite_one(struct commit **pp)
+{
+	for (;;) {
+		struct commit *p = *pp;
+		if (p->object.flags & (TREECHANGE | UNINTERESTING))
+			return 0;
+		if (!p->parents)
+			return -1;
+		*pp = p->parents->item;
+	}
+}
+
+static void rewrite_parents(struct commit *commit)
+{
+	struct commit_list **pp = &commit->parents;
+	while (*pp) {
+		struct commit_list *parent = *pp;
+		if (rewrite_one(&parent->item) < 0) {
+			*pp = parent->next;
+			continue;
+		}
+		pp = &parent->next;
+	}
+}
+
+struct commit *get_revision(struct rev_info *revs)
+{
+	struct commit_list *list = revs->commits;
+	struct commit *commit;
+
+	if (!list)
+		return NULL;
+
+	/* Check the max_count ... */
+	commit = list->item;
+	switch (revs->max_count) {
+	case -1:
+		break;
+	case 0:
+		return NULL;
+	default:
+		revs->max_count--;
+	}
+
+	do {
+		commit = pop_most_recent_commit(&revs->commits, SEEN);
+		if (commit->object.flags & (UNINTERESTING|SHOWN))
+			continue;
+		if (revs->min_age != -1 && (commit->date > revs->min_age))
+			continue;
+		if (revs->max_age != -1 && (commit->date < revs->max_age))
+			return NULL;
+		if (revs->no_merges && commit->parents && commit->parents->next)
+			continue;
+		if (revs->paths && revs->dense) {
+			if (!(commit->object.flags & TREECHANGE))
+				continue;
+			rewrite_parents(commit);
+		}
+		commit->object.flags |= SHOWN;
+		return commit;
+	} while (revs->commits);
+	return NULL;
+}
diff --git a/revision.h b/revision.h
new file mode 100644
index 0000000000..31e8f61567
--- /dev/null
+++ b/revision.h
@@ -0,0 +1,57 @@
+#ifndef REVISION_H
+#define REVISION_H
+
+#define SEEN		(1u<<0)
+#define UNINTERESTING   (1u<<1)
+#define TREECHANGE	(1u<<2)
+#define SHOWN		(1u<<3)
+#define TMP_MARK	(1u<<4) /* for isolated cases; clean after use */
+
+struct rev_info {
+	/* Starting list */
+	struct commit_list *commits;
+	struct object_list *pending_objects;
+
+	/* Basic information */
+	const char *prefix;
+	const char **paths;
+
+	/* Traversal flags */
+	unsigned int	dense:1,
+			no_merges:1,
+			remove_empty_trees:1,
+			lifo:1,
+			topo_order:1,
+			tag_objects:1,
+			tree_objects:1,
+			blob_objects:1,
+			edge_hint:1,
+			limited:1,
+			unpacked:1;
+
+	/* special limits */
+	int max_count;
+	unsigned long max_age;
+	unsigned long min_age;
+};
+
+/* revision.c */
+extern int setup_revisions(int argc, const char **argv, struct rev_info *revs, const char *def);
+extern void prepare_revision_walk(struct rev_info *revs);
+extern struct commit *get_revision(struct rev_info *revs);
+
+extern void mark_parents_uninteresting(struct commit *commit);
+extern void mark_tree_uninteresting(struct tree *tree);
+
+struct name_path {
+	struct name_path *up;
+	int elem_len;
+	const char *elem;
+};
+
+extern struct object_list **add_object(struct object *obj,
+				       struct object_list **p,
+				       struct name_path *path,
+				       const char *name);
+
+#endif
diff --git a/t/t6001-rev-list-merge-order.sh b/t/t6001-rev-list-merge-order.sh
deleted file mode 100755
index 7724e8a8c5..0000000000
--- a/t/t6001-rev-list-merge-order.sh
+++ /dev/null
@@ -1,462 +0,0 @@
-#!/bin/sh
-#
-# Copyright (c) 2005 Jon Seymour
-#
-
-test_description='Tests git-rev-list --merge-order functionality'
-
-. ./test-lib.sh
-. ../t6000lib.sh # t6xxx specific functions
-
-# test-case specific test function
-check_adjacency()
-{
-    read previous
-    echo "= $previous"
-    while read next
-    do
-        if ! (git-cat-file commit $previous | grep "^parent $next" >/dev/null)
-        then
-            echo "^ $next"
-        else
-            echo "| $next"
-        fi
-        previous=$next
-    done
-}
-
-list_duplicates()
-{
-    "$@" | sort | uniq -d
-}
-
-grep_stderr()
-{
-    args=$1
-    shift 1
-    "$@" 2>&1 | grep "$args"
-}
-
-date >path0
-git-update-index --add path0
-save_tag tree git-write-tree
-on_committer_date "1971-08-16 00:00:00" hide_error save_tag root unique_commit root tree
-on_committer_date "1971-08-16 00:00:01" save_tag l0 unique_commit l0 tree -p root
-on_committer_date "1971-08-16 00:00:02" save_tag l1 unique_commit l1 tree -p l0
-on_committer_date "1971-08-16 00:00:03" save_tag l2 unique_commit l2 tree -p l1
-on_committer_date "1971-08-16 00:00:04" save_tag a0 unique_commit a0 tree -p l2
-on_committer_date "1971-08-16 00:00:05" save_tag a1 unique_commit a1 tree -p a0
-on_committer_date "1971-08-16 00:00:06" save_tag b1 unique_commit b1 tree -p a0
-on_committer_date "1971-08-16 00:00:07" save_tag c1 unique_commit c1 tree -p b1
-on_committer_date "1971-08-16 00:00:08" as_author foobar@example.com save_tag b2 unique_commit b2 tree -p b1
-on_committer_date "1971-08-16 00:00:09" save_tag b3 unique_commit b2 tree -p b2
-on_committer_date "1971-08-16 00:00:10" save_tag c2 unique_commit c2 tree -p c1 -p b2
-on_committer_date "1971-08-16 00:00:11" save_tag c3 unique_commit c3 tree -p c2
-on_committer_date "1971-08-16 00:00:12" save_tag a2 unique_commit a2 tree -p a1
-on_committer_date "1971-08-16 00:00:13" save_tag a3 unique_commit a3 tree -p a2
-on_committer_date "1971-08-16 00:00:14" save_tag b4 unique_commit b4 tree -p b3 -p a3
-on_committer_date "1971-08-16 00:00:15" save_tag a4 unique_commit a4 tree -p a3 -p b4 -p c3
-on_committer_date "1971-08-16 00:00:16" save_tag l3 unique_commit l3 tree -p a4
-on_committer_date "1971-08-16 00:00:17" save_tag l4 unique_commit l4 tree -p l3
-on_committer_date "1971-08-16 00:00:18" save_tag l5 unique_commit l5 tree -p l4
-on_committer_date "1971-08-16 00:00:19" save_tag m1 unique_commit m1 tree -p a4 -p c3
-on_committer_date "1971-08-16 00:00:20" save_tag m2 unique_commit m2 tree -p c3 -p a4
-on_committer_date "1971-08-16 00:00:21" hide_error save_tag alt_root unique_commit alt_root tree
-on_committer_date "1971-08-16 00:00:22" save_tag r0 unique_commit r0 tree -p alt_root
-on_committer_date "1971-08-16 00:00:23" save_tag r1 unique_commit r1 tree -p r0
-on_committer_date "1971-08-16 00:00:24" save_tag l5r1 unique_commit l5r1 tree -p l5 -p r1
-on_committer_date "1971-08-16 00:00:25" save_tag r1l5 unique_commit r1l5 tree -p r1 -p l5
-
-
-#
-# note: as of 20/6, it isn't possible to create duplicate parents, so this
-# can't be tested.
-#
-#on_committer_date "1971-08-16 00:00:20" save_tag m3 unique_commit m3 tree -p c3 -p a4 -p c3
-hide_error save_tag e1 as_author e@example.com unique_commit e1 tree
-save_tag e2 as_author e@example.com unique_commit e2 tree -p e1
-save_tag f1 as_author f@example.com unique_commit f1 tree -p e1
-save_tag e3 as_author e@example.com unique_commit e3 tree -p e2
-save_tag f2 as_author f@example.com unique_commit f2 tree -p f1
-save_tag e4 as_author e@example.com unique_commit e4 tree -p e3 -p f2
-save_tag e5 as_author e@example.com unique_commit e5 tree -p e4
-save_tag f3 as_author f@example.com unique_commit f3 tree -p f2
-save_tag f4 as_author f@example.com unique_commit f4 tree -p f3
-save_tag e6 as_author e@example.com unique_commit e6 tree -p e5 -p f4
-save_tag f5 as_author f@example.com unique_commit f5 tree -p f4
-save_tag f6 as_author f@example.com unique_commit f6 tree -p f5 -p e6
-save_tag e7 as_author e@example.com unique_commit e7 tree -p e6
-save_tag e8 as_author e@example.com unique_commit e8 tree -p e7
-save_tag e9 as_author e@example.com unique_commit e9 tree -p e8
-save_tag f7 as_author f@example.com unique_commit f7 tree -p f6
-save_tag f8 as_author f@example.com unique_commit f8 tree -p f7
-save_tag f9 as_author f@example.com unique_commit f9 tree -p f8
-save_tag e10 as_author e@example.com unique_commit e1 tree -p e9 -p f8
-
-hide_error save_tag g0 unique_commit g0 tree
-save_tag g1 unique_commit g1 tree -p g0
-save_tag h1 unique_commit g2 tree -p g0
-save_tag g2 unique_commit g3 tree -p g1 -p h1
-save_tag h2 unique_commit g4 tree -p g2
-save_tag g3 unique_commit g5 tree -p g2
-save_tag g4 unique_commit g6 tree -p g3 -p h2
-
-git-update-ref HEAD $(tag l5)
-
-test_output_expect_success 'rev-list has correct number of entries' 'git-rev-list HEAD | wc -l | tr -d \" \"' <<EOF
-19
-EOF
-
-if git-rev-list --merge-order HEAD 2>&1 | grep 'OpenSSL not linked' >/dev/null
-then
-    test_expect_success 'skipping merge-order test' :
-    test_done
-    exit
-fi
-
-normal_adjacency_count=$(git-rev-list HEAD | check_adjacency | grep -c "\^" | tr -d ' ')
-merge_order_adjacency_count=$(git-rev-list --merge-order HEAD | check_adjacency | grep -c "\^" | tr -d ' ')
-test_expect_success '--merge-order produces as many or fewer discontinuities' '[ $merge_order_adjacency_count -le $normal_adjacency_count ]'
-test_output_expect_success 'simple merge order' 'git-rev-list --merge-order --show-breaks HEAD' <<EOF
-= l5
-| l4
-| l3
-= a4
-| c3
-| c2
-| c1
-^ b4
-| b3
-| b2
-| b1
-^ a3
-| a2
-| a1
-= a0
-| l2
-| l1
-| l0
-= root
-EOF
-
-test_output_expect_success 'two diamonds merge order (g6)' 'git-rev-list --merge-order --show-breaks g4' <<EOF
-= g4
-| h2
-^ g3
-= g2
-| h1
-^ g1
-= g0
-EOF
-
-test_output_expect_success 'multiple heads' 'git-rev-list --merge-order a3 b3 c3' <<EOF
-c3
-c2
-c1
-b3
-b2
-b1
-a3
-a2
-a1
-a0
-l2
-l1
-l0
-root
-EOF
-
-test_output_expect_success 'multiple heads, prune at a1' 'git-rev-list --merge-order a3 b3 c3 ^a1' <<EOF
-c3
-c2
-c1
-b3
-b2
-b1
-a3
-a2
-EOF
-
-test_output_expect_success 'multiple heads, prune at l1' 'git-rev-list --merge-order a3 b3 c3 ^l1' <<EOF
-c3
-c2
-c1
-b3
-b2
-b1
-a3
-a2
-a1
-a0
-l2
-EOF
-
-test_output_expect_success 'cross-epoch, head at l5, prune at l1' 'git-rev-list --merge-order l5 ^l1' <<EOF
-l5
-l4
-l3
-a4
-c3
-c2
-c1
-b4
-b3
-b2
-b1
-a3
-a2
-a1
-a0
-l2
-EOF
-
-test_output_expect_success 'duplicated head arguments' 'git-rev-list --merge-order l5 l5 ^l1' <<EOF
-l5
-l4
-l3
-a4
-c3
-c2
-c1
-b4
-b3
-b2
-b1
-a3
-a2
-a1
-a0
-l2
-EOF
-
-test_output_expect_success 'prune near merge' 'git-rev-list --merge-order a4 ^c3' <<EOF
-a4
-b4
-b3
-a3
-a2
-a1
-EOF
-
-test_output_expect_success "head has no parent" 'git-rev-list --merge-order --show-breaks root' <<EOF
-= root
-EOF
-
-test_output_expect_success "two nodes - one head, one base" 'git-rev-list --merge-order --show-breaks l0' <<EOF
-= l0
-= root
-EOF
-
-test_output_expect_success "three nodes one head, one internal, one base" 'git-rev-list --merge-order --show-breaks l1' <<EOF
-= l1
-| l0
-= root
-EOF
-
-test_output_expect_success "linear prune l2 ^root" 'git-rev-list --merge-order --show-breaks l2 ^root' <<EOF
-^ l2
-| l1
-| l0
-EOF
-
-test_output_expect_success "linear prune l2 ^l0" 'git-rev-list --merge-order --show-breaks l2 ^l0' <<EOF
-^ l2
-| l1
-EOF
-
-test_output_expect_success "linear prune l2 ^l1" 'git-rev-list --merge-order --show-breaks l2 ^l1' <<EOF
-^ l2
-EOF
-
-test_output_expect_success "linear prune l5 ^a4" 'git-rev-list --merge-order --show-breaks l5 ^a4' <<EOF
-^ l5
-| l4
-| l3
-EOF
-
-test_output_expect_success "linear prune l5 ^l3" 'git-rev-list --merge-order --show-breaks l5 ^l3' <<EOF
-^ l5
-| l4
-EOF
-
-test_output_expect_success "linear prune l5 ^l4" 'git-rev-list --merge-order --show-breaks l5 ^l4' <<EOF
-^ l5
-EOF
-
-test_output_expect_success "max-count 10 - merge order" 'git-rev-list --merge-order --show-breaks --max-count=10 l5' <<EOF
-= l5
-| l4
-| l3
-= a4
-| c3
-| c2
-| c1
-^ b4
-| b3
-| b2
-EOF
-
-test_output_expect_success "max-count 10 - non merge order" 'git-rev-list --max-count=10 l5' <<EOF
-l5
-l4
-l3
-a4
-b4
-a3
-a2
-c3
-c2
-b3
-EOF
-
-test_output_expect_success '--max-age=c3, no --merge-order' "git-rev-list --max-age=$(commit_date c3) l5" <<EOF
-l5
-l4
-l3
-a4
-b4
-a3
-a2
-c3
-EOF
-
-test_output_expect_success '--max-age=c3, --merge-order' "git-rev-list --merge-order --max-age=$(commit_date c3) l5" <<EOF
-l5
-l4
-l3
-a4
-c3
-b4
-a3
-a2
-EOF
-
-test_output_expect_success 'one specified head reachable from another a4, c3, --merge-order' "list_duplicates git-rev-list --merge-order a4 c3" <<EOF
-EOF
-
-test_output_expect_success 'one specified head reachable from another c3, a4, --merge-order' "list_duplicates git-rev-list --merge-order c3 a4" <<EOF
-EOF
-
-test_output_expect_success 'one specified head reachable from another a4, c3, no --merge-order' "list_duplicates git-rev-list a4 c3" <<EOF
-EOF
-
-test_output_expect_success 'one specified head reachable from another c3, a4, no --merge-order' "list_duplicates git-rev-list c3 a4" <<EOF
-EOF
-
-test_output_expect_success 'graph with c3 and a4 parents of head' "list_duplicates git-rev-list m1" <<EOF
-EOF
-
-test_output_expect_success 'graph with a4 and c3 parents of head' "list_duplicates git-rev-list m2" <<EOF
-EOF
-
-test_expect_success "head ^head --merge-order" 'git-rev-list --merge-order --show-breaks a3 ^a3' <<EOF
-EOF
-
-#
-# can't test this now - duplicate parents can't be created
-#
-#test_output_expect_success 'duplicate parents' 'git-rev-list --parents --merge-order --show-breaks m3' <<EOF
-#= m3 c3 a4 c3
-#| a4 c3 b4 a3
-#| b4 a3 b3
-#| b3 b2
-#^ a3 a2
-#| a2 a1
-#| a1 a0
-#^ c3 c2
-#| c2 b2 c1
-#| b2 b1
-#^ c1 b1
-#| b1 a0
-#= a0 l2
-#| l2 l1
-#| l1 l0
-#| l0 root
-#= root
-#EOF
-
-test_expect_success "head ^head no --merge-order" 'git-rev-list a3 ^a3' <<EOF
-EOF
-
-test_output_expect_success 'simple merge order (l5r1)' 'git-rev-list --merge-order --show-breaks l5r1' <<EOF
-= l5r1
-| r1
-| r0
-| alt_root
-^ l5
-| l4
-| l3
-| a4
-| c3
-| c2
-| c1
-^ b4
-| b3
-| b2
-| b1
-^ a3
-| a2
-| a1
-| a0
-| l2
-| l1
-| l0
-= root
-EOF
-
-test_output_expect_success 'simple merge order (r1l5)' 'git-rev-list --merge-order --show-breaks r1l5' <<EOF
-= r1l5
-| l5
-| l4
-| l3
-| a4
-| c3
-| c2
-| c1
-^ b4
-| b3
-| b2
-| b1
-^ a3
-| a2
-| a1
-| a0
-| l2
-| l1
-| l0
-| root
-^ r1
-| r0
-= alt_root
-EOF
-
-test_output_expect_success "don't print things unreachable from one branch" "git-rev-list a3 ^b3 --merge-order" <<EOF
-a3
-a2
-a1
-EOF
-
-test_output_expect_success "--merge-order a4 l3" "git-rev-list --merge-order a4 l3" <<EOF
-l3
-a4
-c3
-c2
-c1
-b4
-b3
-b2
-b1
-a3
-a2
-a1
-a0
-l2
-l1
-l0
-root
-EOF
-
-#
-#
-
-test_done