Modify git-rev-list to linearise the commit history in merge order.

PATCH New Jon Seymour 1 participant 2 messages Jun 15, 2016 1 message not in the archive Kbuild

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Jon Seymour

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2016-06-15 22:41 UTC #1 lore raw

PATCH 1/1 Modify git-rev-list to linearise the commit history in merge order.

[PATCH] Modify git-rev-list to linearise the commit history in merge order.

This patch linearises the GIT commit history graph into merge order which is defined by invariants specified in Documentation/git-rev-list.txt.

The linearisation produced by this patch is superior in an objective sense to that produced by the existing git-rev-list implementation in that the linearisation produced is guaranteed to have the minimum number of discontinuities, where a discontinuity is defined as an adjacent pair of commits in the output list which are not related in a direct child-parent relationship.

A test script, t/t5000-rev-list.sh, includes a test which demonstrates that the linearisation produced by --merge-order has less discontinuities than the linearisation produced by git-rev-list without the --merge-order flag specified. To see this, do the following:

        cd t
        ./t5000-rev-list.sh
        cd trash
        cat actual-default-order
        cat actual-merge-order

The existing behaviour of git-rev-list is preserved, by default. To obtain the modified behaviour, specify --merge-order or --merge-order --show-breaks on the command line.

This version of the patch has been tested on the git repository and also on the linux-2.6
repository and has reasonable performance on both.

For more details about this change, refer to Documentation/git-rev-list.txt and http://blackcubes.dyndns.org/epoch/.

Signed-off-by Jon Seymour <[email protected]>

---

Makefile +3 -2

@@ -40,9 +40,9 @@ install: $(PROG) $(SCRIPTS)
        $(INSTALL) $(PROG) $(SCRIPTS) $(dest)$(bin)
 
 LIB_OBJS=read-cache.o sha1_file.o usage.o object.o commit.o tree.o blob.o \
-        tag.o delta.o date.o index.o diff-delta.o patch-delta.o
+        tag.o delta.o date.o index.o diff-delta.o patch-delta.o epoch.o
 LIB_FILE=libgit.a
-LIB_H=cache.h object.h blob.h tree.h commit.h tag.h delta.h
+LIB_H=cache.h object.h blob.h tree.h commit.h tag.h delta.h epoch.h
 
 LIB_H += strbuf.h
 LIB_OBJS += strbuf.o

@@ -134,6 +134,7 @@ diffcore-pathspec.o : $(LIB_H) diffcore.
 diffcore-pickaxe.o : $(LIB_H) diffcore.h
 diffcore-break.o : $(LIB_H) diffcore.h
 diffcore-order.o : $(LIB_H) diffcore.h
+epoch.o: $(LIB_H)
 
 test: all
        $(MAKE) -C t/ all

commit.c +23 -1

@@ -129,7 +129,7 @@ void free_commit_list(struct commit_list
        }
 }
 
-static void insert_by_date(struct commit_list **list, struct commit *item)
+void insert_by_date(struct commit_list **list, struct commit *item)
 {
        struct commit_list **pp = list;
        struct commit_list *p;

@@ -254,3 +254,25 @@ unsigned long pretty_print_commit(const
        buf[offset] = '\0';
        return offset;
 }
+
+struct commit *pop_commit(struct commit_list **stack)
+{
+       struct commit_list *top = *stack;
+       struct commit *item = top ? top->item : NULL;
+
+       if (top) {
+               *stack = top->next;
+               free(top);
+       }
+       return item;
+}
+
+int count_parents(struct commit * commit)
+{
+        int count = 0;
+        struct commit_list * parents = commit->parents;
+        for (count=0;parents; parents=parents->next,count++)
+          ;
+        return count;
+}
+

commit.h +2 -0

@@ -32,6 +32,8 @@ void free_commit_list(struct commit_list
 
 void sort_by_date(struct commit_list **list);
 
+void insert_by_date(struct commit_list **list, struct commit *item);
+
 extern unsigned long pretty_print_commit(const char *msg, unsigned

long len, char *buf, unsigned long space);

@@ -41,4 +43,7 @@ extern unsigned long pretty_print_commit
struct commit *pop_most_recent_commit(struct commit_list **list,

                                      unsigned int mark);

+struct commit *pop_commit(struct commit_list **stack); +
+int count_parents(struct commit * commit);
#endif /* COMMIT_H */

epoch.c new file +6 -0

new file mode 100644
@@ -0,0 +1,454 @@
+/*
+ * 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>
+#include <openssl/bn.h> // provides arbitrary
precision integers required to accurately represent fractional mass +#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()
+{
+ if (!context) {
+ context = BN_CTX_new();
+ }
+ return context;
+}
+
+static struct fraction *new_zero()
+{

+       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()
+{
+ if (!one) {
+ one = new_zero();
+ BN_one(&one->numerator);
+ }
+ return one;
+}
+
+static struct fraction *get_zero()
+{
+ 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());
+
+ 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 node of an epoch.
+//
+// This algorithm uses a conservation of mass approach.
+//
+// The head starts with a weight of 1 and distributes equal portions +// along each edge to each of its parents. The process continues until +// one node discovers that it has acquired a total mass of 1 from its +// descendents. This node is the base node.
+//
+// Importantly the queue of nodes to be processed is sorted in +// reverse date order and each node occupies at most one
+// position in the queue simultaneously. These two properties +// do not effect the algorithm's correctness. However assuming most, but +// not all, timestamps are sane they do prevent the algorithm becoming +// exponential by ensuring that most nodes are only visited once. +// This is true because mass is only propagated through the network +// when we are pretty sure we are not going to see any more coming +// our way. The occasional bad timestamp will mean that we are +// wrong, occasionally, but this does not matter too much. +//
+static int find_base(struct commit *head, struct commit **boundary) +{
+ int ret = 0;
+
+ struct commit_list *cleaner = NULL;
+ struct commit_list *pending = NULL;
+
+ *boundary = NULL;
+
+ // we inject a mass of 1 unit here
+
+ new_mass_counter(head, get_one());
+
+ commit_list_insert(head, &pending);
+ commit_list_insert(head, &cleaner);
+
+ while (!*boundary && pending && !ret) {
+
+ struct commit *latest = pop_commit(&pending);
+ struct mass_counter *latest_node = (struct
mass_counter *) latest->object.util;
+
+ if ((ret = parse_commit(latest)))
+ continue;
+
+ add(&latest_node->seen, &latest_node->seen,
&latest_node->pending);
+
+ int num_parents = count_parents(latest);
+
+ if (num_parents) {
+
+ struct fraction distribution;
+
+ divide(init_fraction(&distribution),
&latest_node->pending, num_parents);
+
+ struct commit_list *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);
+ commit_list_insert(parent, &cleaner);
+ insert_by_date(&pending, parent);
+ } else {
+ if
(!compare(&parent_node->pending, get_zero())) {
+
copy(&parent_node->pending, &distribution);
+
insert_by_date(&pending, parent);
+ } else {
+
add(&parent_node->pending, &parent_node->pending, &distribution);
+ }
+ }
+ }
+ }
+
+ if (!compare(&latest_node->seen, get_one()) && (latest
!= head)) {
+ // if this node has seen one unit of mass, it
must be the base, so mark
+ // the boundary which will cause the loop to stop.
+ *boundary = latest;
+ }
+
+ copy(&latest_node->pending, get_zero());
+
+ }
+
+ for (; 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);
+
+ 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
+
+ // traverse to the end of a maximal linear epoch
+ 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;
+}
+
+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 & MERGE_ORDER_BREAK_FLAG)) {
+ if (is_parent_of(top->item, item)) {
+ top->item->object.flags &= ~MERGE_ORDER_BREAK_FLAG;
+ }
+ }
+ commit_list_insert(item, stack);
+}
+
+//
+// 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) +{
+ parse_commit(head);
+
+ head->object.flags |= MERGE_ORDER_VISIT_FLAG;
+
+ struct commit_list *parents;
+
+ struct commit_list *reversed_parents = NULL;
+
+ //
+ // parse_commit builds the parent list in reverse order with
respect to the order of

+       // the git-commit-tree arguments.
+       //
+       // so we need to reverse this list to output the oldest (or

most "local") commits last.
+ //
+
+ for (parents = head->parents; parents; parents = parents->next) {
+ commit_list_insert(parents->item, &reversed_parents);
+ }
+

+       //
+       // 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 (; reversed_parents;) {
+               struct commit *parent = pop_commit(&reversed_parents);
+               parse_commit(parent);
+               if (!(parent->object.flags & MERGE_ORDER_VISIT_FLAG)) {

+ if (parent->object.flags & MERGE_ORDER_EPOCH_FLAG) {
+ if (*stack) {
+ die("something else is on the
stack - %s\n", sha1_to_hex((*stack)->item->object.sha1));

+                               }
+                               push_onto_merge_order_stack(stack, parent);
+                               parent->object.flags |= MERGE_ORDER_VISIT_FLAG;

+ } else {
+ sort_first_epoch(parent, stack);
+ if (reversed_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
|= MERGE_ORDER_BREAK_FLAG;
+ }
+ }
+ }
+ }
+
+ push_onto_merge_order_stack(stack, head);
+}
+
+//
+// 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. +//
+int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitter) +{

+       struct commit *next;
+       int ret = 0;
+       int stop = 0;

+
+ parse_commit(head_of_epoch);
+
+ for (next = head_of_epoch; next && next->parents && !ret && !stop;) {
+
+ struct commit *base = NULL;
+
+ ret = find_next_epoch_boundary(next, &base);
+ if (ret)
+ return ret;
+
+ next->object.flags |= MERGE_ORDER_EPOCH_FLAG;
+ if (base) {
+ base->object.flags |= MERGE_ORDER_EPOCH_FLAG;
+ }
+
+ if (HAS_EXACTLY_ONE_PARENT(next)) {
+
+ while (HAS_EXACTLY_ONE_PARENT(next) && !stop && !ret) {

+                               stop = (*emitter) (next);
+                               next = next->parents->item;
+                               ret = parse_commit(next);

+ }
+
+ } else {
+

+                       struct commit_list *stack = NULL;
+                       sort_first_epoch(next, &stack);
+                       for (; stack && !stop;) {

+ next = pop_commit(&stack);
+ if (stack) {
+ stop = (*emitter) (next);
+ }
+ }
+ if (stack) {
+ free_commit_list(stack);
+ }
+ }
+
+ }
+
+ if (next && !stop) {
+ stop = (*emitter) (next);
+ }
+
+ return ret;
+}

epoch.h new file +12 -0

new file mode 100644
@@ -0,0 +1,12 @@
+#ifndef EPOCH_H
+#define EPOCH_H
+
+typedef int (*emitter_func) (struct commit *);
+
+int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitter);
+
+#define MERGE_ORDER_EPOCH_FLAG (1u<<3)
+#define MERGE_ORDER_VISIT_FLAG (1u<<4)
+#define MERGE_ORDER_BREAK_FLAG (1u<<5)
+
+#endif                         /* EPOCH_H */

object.h +1 -0

@@ -15,6 +15,7 @@ struct object {
        const char *type;
        struct object_list *refs;
        struct object_list *attached_deltas;
+       void *util;
 };
 
 extern int nr_objs;

rev-list.c +7 -1

@@ -1,5 +1,6 @@
 #include "cache.h"
 #include "commit.h"
+#include "epoch.h"
 
 #define SEEN           (1u << 0)
 #define INTERESTING    (1u << 1)

@@ -11,7 +12,8 @@ static const char rev_list_usage[] =
                      "  --max-age=epoch\n"
                      "  --min-age=epoch\n"
                      "  --header\n"
-                     "  --pretty";
+                     "  --pretty\n"
+                     "  --merge-order [ --show-breaks ]";
 
 static void mark_parents_uninteresting(struct commit *commit)
 {

@@ -36,18 +38,63 @@ static int everybody_uninteresting(struc
        return 1;
 }
 
+static unsigned long max_age = -1;
+static unsigned long min_age = -1;
+static int max_count = -1;
+static int verbose_header = 0, show_parents = 0, pretty_print = 0,

merge_order = 0, show_breaks = 0;
+static const char *prefix = "";
+static int hdr_termination = 0;
+
+static int process_commit(struct commit * commit) +{
+ if (commit->object.flags & UNINTERESTING)
+ return 0;
+ if (min_age != -1 && (commit->date > min_age))
+ return 0;
+ if (max_age != -1 && (commit->date < max_age))
+ return 1;
+ if (max_count != -1 && !max_count--)
+ return 1;
+
+ if (!show_breaks) {
+ printf("%s%s", prefix, sha1_to_hex(commit->object.sha1));
+ if (show_parents) {
+ struct commit_list *parents = commit->parents;
+ while (parents) {
+ printf(" %s",
sha1_to_hex(parents->item->object.sha1));
+ parents = parents->next;
+ }

+               }
+               putchar('\n');
+               if (verbose_header) {

+ const char *buf = commit->buffer;
+ if (pretty_print) {
+ static char pretty_header[16384];
+ pretty_print_commit(commit->buffer,
~0, pretty_header, sizeof(pretty_header));
+ buf = pretty_header;
+ }
+ printf("%s%c", buf, hdr_termination);
+ }
+ } else {
+ char c='|';
+ if (commit->object.flags & MERGE_ORDER_BREAK_FLAG) {
+ c = '^';
+ } else if (commit->object.flags & MERGE_ORDER_EPOCH_FLAG) {
+ c = '=';
+ }
+ printf("%c %s\n", c, sha1_to_hex(commit->object.sha1));
+ }
+
+ return 0;
+}
+
int main(int argc, char **argv)

 {
        int nr_sha;
        unsigned char sha1[2][20];
        struct commit_list *list = NULL;
        struct commit *commit, *end;
-       int i, verbose_header = 0, show_parents = 0, pretty_print = 0;
-       int hdr_termination = 0;
-       const char *prefix = "";
-       unsigned long max_age = -1;
-       unsigned long min_age = -1;
-       int max_count = -1;
+       int i;

        nr_sha = 0;
        for (i = 1 ; i < argc; i++) {
@@ -80,8 +127,16 @@ int main(int argc, char **argv)
                        show_parents = 1;
                        continue;
                }

+ if (!strncmp(arg, "--merge-order", 13)) {
+ merge_order = 1;
+ continue;
+ }
+ if (!strncmp(arg, "--show-breaks", 13)) {
+ show_breaks = 1;
+ continue;
+ }

-               if (nr_sha > 2 || get_sha1(arg, sha1[nr_sha]))
+               if (nr_sha > 2 || get_sha1(arg, sha1[nr_sha])||
(show_breaks && !merge_order))
                        usage(rev_list_usage);
                nr_sha++;
        }
@@ -118,36 +173,19 @@ int main(int argc, char **argv)
                } while (list);
                list = newlist;
        }

+
+ if (!merge_order) {
+ while (list) {
+ struct commit *commit =
pop_most_recent_commit(&list, SEEN);
+ if (process_commit(commit)) {
+ break;
+ }
+ }
+ } else {
+ if (sort_in_merge_order(commit, &process_commit)) {
+ die("merge order sort failed\n");
+ }
+ }

- while (list) {
- struct commit *commit = pop_most_recent_commit(&list, SEEN);
-
- if (commit->object.flags & UNINTERESTING)
- continue;
- if (min_age != -1 && (commit->date > min_age))
- continue;
- if (max_age != -1 && (commit->date < max_age))
- break;
- if (max_count != -1 && !max_count--)
- break;
- printf("%s%s", prefix, sha1_to_hex(commit->object.sha1));
- if (show_parents) {
- struct commit_list *parents = commit->parents;
- while (parents) {
- printf(" %s",
sha1_to_hex(parents->item->object.sha1));
- parents = parents->next;
- }

-               }
-               putchar('\n');
-               if (verbose_header) {

- const char *buf = commit->buffer;
- if (pretty_print) {
- static char pretty_header[16384];
- pretty_print_commit(commit->buffer,
~0, pretty_header, sizeof(pretty_header));
- buf = pretty_header;
- }
- printf("%s%c", buf, hdr_termination);
- }
- }

        return 0;

}

t/t5000-rev-list.sh new file +60 -0

60 lines not on this page · raw message

actual-merge-order
+cat > expected-merge-order <<EOF

+= a4
+| c3
+| c2
+| c1
+^ b4
+| b3
+| b2
+| b1
+^ a3
+| a2
+| a1
+| a0

+= root
+EOF
+
+git-rev-list HEAD | check_adjacency | sed "$(sed_script)" > actual-default-order +normal_adjacency_count=$(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 'Testing that the rev-list has correct number of entries' '[ $(git-rev-list HEAD | wc -l) -eq 13 ]' +test_expect_success 'Testing that --merge-order produces the correct result' 'diff expected-merge-order actual-merge-order' +test_expect_success 'Testing that --merge-order produces as many or fewer discontinuities' '[ $merge_order_adjacency_count -le $normal_adjacency_count ]'
+
+test_done

Signature · 2 lines

homepage: http://www.zeta.org.au/~jon/
blog: http://orwelliantremors.blogspot.com/

Jon Seymour

author

2016-06-15 22:41 UTC #2 lore raw

PATCH 1/1 Modify git-rev-list to linearise the commit history in merge order. [ pox on the house of gmail ]

Pox on the house of gmail!

A non-wrapped version of the patch can be downloaded from:

http://blackcubes.dyndns.org/epoch/epoch.patch

More info about the patch can be read here:

http://blackcubes.dyndns.org/epoch/

Discussion to the list please.

jon.
---------- Forwarded message ----------
From: Jon Seymour <[email protected]>
Date: Jun 3, 2005 1:16 AM
Subject: [PATCH] Modify git-rev-list to linearise the commit history in merge order.
To: Git Mailing List <[email protected]>
Cc: Linus Torvalds <[email protected]>, Paul Mackerras <[email protected]>

[PATCH] Modify git-rev-list to linearise the commit history in merge order.

This patch linearises the GIT commit history graph into merge order which is defined by invariants specified in Documentation/git-rev-list.txt.

        cd t
        ./t5000-rev-list.sh
        cd trash
        cat actual-default-order
        cat actual-merge-order

The existing behaviour of git-rev-list is preserved, by default. To obtain the modified behaviour, specify --merge-order or --merge-order --show-breaks on the command line.

This version of the patch has been tested on the git repository and also on the linux-2.6
repository and has reasonable performance on both.

For more details about this change, refer to Documentation/git-rev-list.txt and http://blackcubes.dyndns.org/epoch/.

Signed-off-by Jon Seymour <[email protected]>

---

Makefile +3 -2

@@ -40,9 +40,9 @@ install: $(PROG) $(SCRIPTS)
        $(INSTALL) $(PROG) $(SCRIPTS) $(dest)$(bin)
 
 LIB_OBJS=read-cache.o sha1_file.o usage.o object.o commit.o tree.o blob.o \
-        tag.o delta.o date.o index.o diff-delta.o patch-delta.o
+        tag.o delta.o date.o index.o diff-delta.o patch-delta.o epoch.o
 LIB_FILE=libgit.a
-LIB_H=cache.h object.h blob.h tree.h commit.h tag.h delta.h
+LIB_H=cache.h object.h blob.h tree.h commit.h tag.h delta.h epoch.h
 
 LIB_H += strbuf.h
 LIB_OBJS += strbuf.o

@@ -134,6 +134,7 @@ diffcore-pathspec.o : $(LIB_H) diffcore.
 diffcore-pickaxe.o : $(LIB_H) diffcore.h
 diffcore-break.o : $(LIB_H) diffcore.h
 diffcore-order.o : $(LIB_H) diffcore.h
+epoch.o: $(LIB_H)
 
 test: all
        $(MAKE) -C t/ all

commit.c +23 -1

@@ -129,7 +129,7 @@ void free_commit_list(struct commit_list
        }
 }
 
-static void insert_by_date(struct commit_list **list, struct commit *item)
+void insert_by_date(struct commit_list **list, struct commit *item)
 {
        struct commit_list **pp = list;
        struct commit_list *p;

@@ -254,3 +254,25 @@ unsigned long pretty_print_commit(const
        buf[offset] = '\0';
        return offset;
 }
+
+struct commit *pop_commit(struct commit_list **stack)
+{
+       struct commit_list *top = *stack;
+       struct commit *item = top ? top->item : NULL;
+
+       if (top) {
+               *stack = top->next;
+               free(top);
+       }
+       return item;
+}
+
+int count_parents(struct commit * commit)
+{
+        int count = 0;
+        struct commit_list * parents = commit->parents;
+        for (count=0;parents; parents=parents->next,count++)
+          ;
+        return count;
+}
+

commit.h +2 -0

@@ -32,6 +32,8 @@ void free_commit_list(struct commit_list
 
 void sort_by_date(struct commit_list **list);
 
+void insert_by_date(struct commit_list **list, struct commit *item);
+
 extern unsigned long pretty_print_commit(const char *msg, unsigned

long len, char *buf, unsigned long space);

@@ -41,4 +43,7 @@ extern unsigned long pretty_print_commit
struct commit *pop_most_recent_commit(struct commit_list **list,

                                      unsigned int mark);

+struct commit *pop_commit(struct commit_list **stack); +
+int count_parents(struct commit * commit);
#endif /* COMMIT_H */

epoch.c new file +6 -0

new file mode 100644
@@ -0,0 +1,454 @@
+/*
+ * 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

+       struct fraction *result = xmalloc(sizeof(*result));
+       BN_init(&result->numerator);
+       BN_init(&result->denominator);
+       BN_zero(&result->numerator);
+       BN_one(&result->denominator);
+       return result;

+       BN_init(&fraction->numerator);
+       BN_init(&fraction->denominator);
+       BN_zero(&fraction->numerator);
+       BN_one(&fraction->denominator);
+       return fraction;

+       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,

+       BN_clear(&a);
+       BN_clear(&b);
+       BN_clear(&gcd);

+       clear_fraction(&counter->seen);
+       clear_fraction(&counter->pending);
+       free(counter);

+               struct commit *next = pop_commit(&cleaner);
+               free_mass_counter((struct mass_counter *) next->object.util);
+               next->object.util = NULL;

+       // the git-commit-tree arguments.
+       //
+       // so we need to reverse this list to output the oldest (or

most "local") commits last.
+ //
+
+ for (parents = head->parents; parents; parents = parents->next) {
+ commit_list_insert(parents->item, &reversed_parents);
+ }
+

+       //
+       // 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 (; reversed_parents;) {
+               struct commit *parent = pop_commit(&reversed_parents);
+               parse_commit(parent);
+               if (!(parent->object.flags & MERGE_ORDER_VISIT_FLAG)) {

+ if (parent->object.flags & MERGE_ORDER_EPOCH_FLAG) {
+ if (*stack) {
+ die("something else is on the
stack - %s\n", sha1_to_hex((*stack)->item->object.sha1));

+                               }
+                               push_onto_merge_order_stack(stack, parent);
+                               parent->object.flags |= MERGE_ORDER_VISIT_FLAG;

+                                       // of parent N+1
+                                       //
+                                       // the next push onto the

+       struct commit *next;
+       int ret = 0;
+       int stop = 0;

+                               stop = (*emitter) (next);
+                               next = next->parents->item;
+                               ret = parse_commit(next);

+ }
+
+ } else {
+

+                       struct commit_list *stack = NULL;
+                       sort_first_epoch(next, &stack);
+                       for (; stack && !stop;) {

epoch.h new file +12 -0

new file mode 100644
@@ -0,0 +1,12 @@
+#ifndef EPOCH_H
+#define EPOCH_H
+
+typedef int (*emitter_func) (struct commit *);
+
+int sort_in_merge_order(struct commit *head_of_epoch, emitter_func emitter);
+
+#define MERGE_ORDER_EPOCH_FLAG (1u<<3)
+#define MERGE_ORDER_VISIT_FLAG (1u<<4)
+#define MERGE_ORDER_BREAK_FLAG (1u<<5)
+
+#endif                         /* EPOCH_H */

object.h +1 -0

@@ -15,6 +15,7 @@ struct object {
        const char *type;
        struct object_list *refs;
        struct object_list *attached_deltas;
+       void *util;
 };
 
 extern int nr_objs;

rev-list.c +7 -1

@@ -1,5 +1,6 @@
 #include "cache.h"
 #include "commit.h"
+#include "epoch.h"
 
 #define SEEN           (1u << 0)
 #define INTERESTING    (1u << 1)

@@ -11,7 +12,8 @@ static const char rev_list_usage[] =
                      "  --max-age=epoch\n"
                      "  --min-age=epoch\n"
                      "  --header\n"
-                     "  --pretty";
+                     "  --pretty\n"
+                     "  --merge-order [ --show-breaks ]";
 
 static void mark_parents_uninteresting(struct commit *commit)
 {

@@ -36,18 +38,63 @@ static int everybody_uninteresting(struc
        return 1;
 }
 
+static unsigned long max_age = -1;
+static unsigned long min_age = -1;
+static int max_count = -1;
+static int verbose_header = 0, show_parents = 0, pretty_print = 0,

+               }
+               putchar('\n');
+               if (verbose_header) {

 {
        int nr_sha;
        unsigned char sha1[2][20];
        struct commit_list *list = NULL;
        struct commit *commit, *end;
-       int i, verbose_header = 0, show_parents = 0, pretty_print = 0;
-       int hdr_termination = 0;
-       const char *prefix = "";
-       unsigned long max_age = -1;
-       unsigned long min_age = -1;
-       int max_count = -1;
+       int i;

        nr_sha = 0;
        for (i = 1 ; i < argc; i++) {
@@ -80,8 +127,16 @@ int main(int argc, char **argv)
                        show_parents = 1;
                        continue;
                }

+ if (!strncmp(arg, "--merge-order", 13)) {
+ merge_order = 1;
+ continue;
+ }
+ if (!strncmp(arg, "--show-breaks", 13)) {
+ show_breaks = 1;
+ continue;
+ }

-               if (nr_sha > 2 || get_sha1(arg, sha1[nr_sha]))
+               if (nr_sha > 2 || get_sha1(arg, sha1[nr_sha])||
(show_breaks && !merge_order))
                        usage(rev_list_usage);
                nr_sha++;
        }
@@ -118,36 +173,19 @@ int main(int argc, char **argv)
                } while (list);
                list = newlist;
        }

-               }
-               putchar('\n');
-               if (verbose_header) {

        return 0;

}

t/t5000-rev-list.sh new file +60 -0

60 lines not on this page · raw message

actual-merge-order
+cat > expected-merge-order <<EOF

+= a4
+| c3
+| c2
+| c1
+^ b4
+| b3
+| b2
+| b1
+^ a3
+| a2
+| a1
+| a0

--
homepage: http://www.zeta.org.au/~jon/
blog: http://orwelliantremors.blogspot.com/

Signature · 2 lines

homepage: http://www.zeta.org.au/~jon/
blog: http://orwelliantremors.blogspot.com/