ref: c7dcc82b0be805717efbe77c98eaadf3ee1e31af
parent: 546f8cfeca6fca0b6b246c8dbf035027e3f15f8c
author: Ori Bernstein <ori@eigenstate.org>
date: Sat Sep 11 13:46:26 EDT 2021
git/query: fix spurious merge requests Due to the way LCA is defined, a using a strict LCA on a graph like this: <--a--b--c--d--e--f--g \ / +-----h------- can lead to spurious requests to merge. This happens because 'lca(b, g)' would return 'a', since it can be reached in one step from 'b', and 2 steps from 'g', while reaching 'b' from 'a' would be a longer path. As a result, we need to implement an lca variant that returns the starting node if one is reachable from the other, even if it's already found the technically correct least common ancestor. This replaces our LCA algorithm with one based on the painting we do while finding a twixt, making it give the resutls we want. git/query: fix spurious merge requests Due to the way LCA is defined, a using a strict LCA on a graph like this: <--a--b--c--d--e--f--g \ / +-----h------- can lead to spurious requests to merge. This happens because 'lca(b, g)' would return 'a', since it can be reached in one step from 'b', and 2 steps from 'g', while reaching 'b' from 'a' would be a longer path. As a result, we need to implement an lca variant that returns the starting node if one is reachable from the other, even if it's already found the technically correct least common ancestor. This replaces our LCA algorithm with one based on the painting we do while finding a twixt.
--- a/sys/src/cmd/git/git.h
+++ b/sys/src/cmd/git/git.h
@@ -18,6 +18,8 @@
typedef struct Objlist Objlist;
typedef struct Dtab Dtab;
typedef struct Dblock Dblock;
+typedef struct Objq Objq;
+typedef struct Qelt Qelt;
enum {
Pathmax = 512,
@@ -151,6 +153,20 @@
int sz;
};
+struct Qelt {
+ Object *o;
+ vlong mtime;
+ int color;
+ int dist;
+};
+
+struct Objq {
+ Qelt *heap;
+ int nheap;
+ int heapsz;
+ int nkeep;
+};
+
struct Dtab {
Object *o;
uchar *base;
@@ -301,3 +317,9 @@
int readphase(Conn *);
int writephase(Conn *);
void closeconn(Conn *);
+
+/* queues */
+void qinit(Objq*);
+void qclear(Objq*);
+void qput(Objq*, Object*, int, int);
+int qpop(Objq*, Qelt*);
--- a/sys/src/cmd/git/log.c
+++ b/sys/src/cmd/git/log.c
@@ -15,10 +15,8 @@
char *commitid;
int shortlog;
-Object **heap;
-int nheap;
-int heapsz;
Objset done;
+Objq objq;
Pfilt *pathfilt;
void
@@ -192,64 +190,10 @@
}
static void
-qput(Object *o)
-{
- Object *p;
- int i;
-
- if(oshas(&done, o->hash))
- return;
- osadd(&done, o);
- if(nheap == heapsz){
- heapsz *= 2;
- heap = earealloc(heap, heapsz, sizeof(Object*));
- }
- heap[nheap++] = o;
- for(i = nheap - 1; i > 0; i = (i-1)/2){
- o = heap[i];
- p = heap[(i-1)/2];
- if(o->commit->mtime < p->commit->mtime)
- break;
- heap[i] = p;
- heap[(i-1)/2] = o;
- }
-}
-
-static Object*
-qpop(void)
-{
- Object *o, *t;
- int i, l, r, m;
-
- if(nheap == 0)
- return nil;
-
- i = 0;
- o = heap[0];
- t = heap[--nheap];
- heap[0] = t;
- while(1){
- m = i;
- l = 2*i+1;
- r = 2*i+2;
- if(l < nheap && heap[m]->commit->mtime < heap[l]->commit->mtime)
- m = l;
- if(r < nheap && heap[m]->commit->mtime < heap[r]->commit->mtime)
- m = r;
- else
- break;
- t = heap[m];
- heap[m] = heap[i];
- heap[i] = t;
- i = m;
- }
- return o;
-}
-
-static void
showcommits(char *c)
{
Object *o, *p;
+ Qelt e;
int i;
Hash h;
@@ -259,18 +203,20 @@
sysfatal("resolve %s: %r", c);
if((o = readobject(h)) == nil)
sysfatal("load %H: %r", h);
- heapsz = 8;
- heap = eamalloc(heapsz, sizeof(Object*));
+ qinit(&objq);
osinit(&done);
- qput(o);
- while((o = qpop()) != nil){
- show(o);
- for(i = 0; i < o->commit->nparent; i++){
- if((p = readobject(o->commit->parent[i])) == nil)
+ qput(&objq, o, 0, 0);
+ while(qpop(&objq, &e)){
+ show(e.o);
+ for(i = 0; i < e.o->commit->nparent; i++){
+ if(oshas(&done, e.o->commit->parent[i]))
+ continue;
+ if((p = readobject(e.o->commit->parent[i])) == nil)
sysfatal("load %H: %r", o->commit->parent[i]);
- qput(p);
+ osadd(&done, p);
+ qput(&objq, p, 0, 0);
}
- unref(o);
+ unref(e.o);
}
}
--- a/sys/src/cmd/git/query.c
+++ b/sys/src/cmd/git/query.c
@@ -158,6 +158,7 @@
char query[2048], repo[512];
ARGBEGIN{
+ case 'd': chattygit++; break;
case 'p': fullpath++; break;
case 'c': changes++; break;
case 'r': reverse ^= 1; break;
--- a/sys/src/cmd/git/ref.c
+++ b/sys/src/cmd/git/ref.c
@@ -5,9 +5,21 @@
#include "git.h"
typedef struct Eval Eval;
-typedef struct XObject XObject;
-typedef struct Objq Objq;
+typedef struct Lcaq Lcaq;
+struct Lcaq {
+ Objq;
+
+ Hash *head;
+ Hash *tail;
+ int nhead;
+ int ntail;
+
+ Object *best;
+ int dist;
+};
+
+
enum {
Blank,
Keep,
@@ -22,19 +34,12 @@
int stksz;
};
-struct XObject {
- Object *obj;
- Object *mark;
- XObject *queue;
- XObject *next;
+static char *colors[] = {
+[Keep] "keep",
+[Drop] "drop",
+[Blank] "blank",
};
-struct Objq {
- Objq *next;
- Object *o;
- int color;
-};
-
static Object zcommit = {
.type=GCommit
};
@@ -128,150 +133,98 @@
return 1;
}
-XObject*
-hnode(XObject *ht[], Object *o)
+static int
+pickbest(Lcaq *q, Qelt *e, int color)
{
- XObject *h;
- int hh;
+ int i, best, exact;
- hh = o->hash.h[0] & 0xff;
- for(h = ht[hh]; h; h = h->next)
- if(hasheq(&o->hash, &h->obj->hash))
- return h;
-
- h = emalloc(sizeof(*h));
- h->obj = o;
- h->mark = nil;
- h->queue = nil;
- h->next = ht[hh];
- ht[hh] = h;
- return h;
-}
-
-Object*
-ancestor(Object *a, Object *b)
-{
- Object *o, *p, *r;
- XObject *ht[256];
- XObject *h, *q, *q1, *q2;
- int i;
-
- if(a == b)
- return a;
- if(a == nil || b == nil)
- return nil;
- r = nil;
- memset(ht, 0, sizeof(ht));
- q1 = nil;
-
- h = hnode(ht, a);
- h->mark = a;
- h->queue = q1;
- q1 = h;
-
- h = hnode(ht, b);
- h->mark = b;
- h->queue = q1;
- q1 = h;
-
- while(1){
- q2 = nil;
- while(q = q1){
- q1 = q->queue;
- q->queue = nil;
- o = q->obj;
- for(i = 0; i < o->commit->nparent; i++){
- p = readobject(o->commit->parent[i]);
- if(p == nil)
- goto err;
- h = hnode(ht, p);
- if(h->mark != nil){
- if(h->mark != q->mark){
- r = h->obj;
- goto done;
- }
- } else {
- h->mark = q->mark;
- h->queue = q2;
- q2 = h;
- }
- }
+ best = 0;
+ exact = 0;
+ if(color == Blank || e->color == color)
+ return 0;
+ if(e->dist < q->dist){
+ dprint(1, "found best (dist %d < %d): %H\n", e->dist, q->dist, e->o->hash);
+ best = 1;
+ }
+ for(i = 0; i < q->nhead; i++)
+ if(hasheq(&q->head[i], &e->o->hash)){
+ dprint(1, "found best (exact head): %H\n", e->o->hash);
+ best = 1;
+ exact = 1;
}
- if(q2 == nil){
-err:
- werrstr("no common ancestor");
- break;
+ for(i = 0; i < q->ntail; i++)
+ if(hasheq(&q->tail[i], &e->o->hash)){
+ dprint(1, "found best (exact tail): %H\n", e->o->hash);
+ best = 1;
+ exact = 1;
}
- q1 = q2;
+ if(best){
+ q->best = e->o;
+ q->dist = e->dist;
}
-done:
- for(i=0; i<nelem(ht); i++){
- while(h = ht[i]){
- ht[i] = h->next;
- free(h);
- }
- }
- return r;
+ return exact;
}
-int
-lca(Eval *ev)
-{
- Object *a, *b, *o;
-
- if(ev->nstk < 2){
- werrstr("ancestor needs 2 objects");
- return -1;
- }
- a = pop(ev);
- b = pop(ev);
- o = ancestor(a, b);
- if(o == nil)
- return -1;
- push(ev, o);
- return 0;
-}
-
static int
-repaint(Objset *keep, Objset *drop, Object *o)
+repaint(Lcaq *lcaq, Objset *keep, Objset *drop, Object *o, int dist, int ancestor)
{
+ Lcaq objq;
+ Qelt e;
Object *p;
int i;
- if(!oshas(keep, o->hash) && !oshas(drop, o->hash)){
- dprint(2, "repaint: blank => drop %H\n", o->hash);
- osadd(drop, o);
- return 0;
+ qinit(&objq);
+ if((o = readobject(o->hash)) == nil)
+ return -1;
+ qput(&objq, o, Drop, dist);
+ while(qpop(&objq, &e)){
+ o = e.o;
+ if(oshas(drop, o->hash))
+ continue;
+ if(ancestor && pickbest(lcaq, &e, Keep))
+ goto out;
+ if(!oshas(keep, o->hash)){
+ dprint(2, "repaint: blank => drop %H\n", o->hash);
+ osadd(drop, o);
+ continue;
+ }
+ for(i = 0; i < o->commit->nparent; i++){
+ if(oshas(drop, o->commit->parent[i]))
+ continue;
+ if((p = readobject(o->commit->parent[i])) == nil)
+ goto out;
+ if(p->type != GCommit){
+ fprint(2, "hash %H not commit\n", p->hash);
+ unref(p);
+ }
+ qput(&objq, p, Drop, e.dist+1);
+ }
+ unref(e.o);
}
- if(oshas(keep, o->hash))
- dprint(2, "repaint: keep => drop %H\n", o->hash);
- osadd(drop, o);
- for(i = 0; i < o->commit->nparent; i++){
- if((p = readobject(o->commit->parent[i])) == nil)
- return -1;
- if(repaint(keep, drop, p) == -1)
- return -1;
- unref(p);
- }
+out:
+ qclear(&objq);
return 0;
}
-int
-findtwixt(Hash *head, int nhead, Hash *tail, int ntail, Object ***res, int *nres)
+static int
+paint(Hash *head, int nhead, Hash *tail, int ntail, Object ***res, int *nres, int ancestor)
{
- Objq *q, *e, *n, **p;
+ Qelt e;
+ Lcaq objq;
Objset keep, drop;
Object *o, *c;
int i, ncolor;
- e = nil;
- q = nil;
- p = &q;
osinit(&keep);
osinit(&drop);
+ qinit(&objq);
+ objq.head = head;
+ objq.nhead = nhead;
+ objq.tail = tail;
+ objq.ntail = ntail;
+ objq.dist = 1<<30;
+
for(i = 0; i < nhead; i++){
- if(hasheq(&head[i], &Zhash))
- continue;
if((o = readobject(head[i])) == nil){
fprint(2, "warning: %H does not point at commit\n", o->hash);
werrstr("read head %H: %r", head[i]);
@@ -282,17 +235,11 @@
unref(o);
continue;
}
- dprint(1, "twixt init: keep %H\n", o->hash);
- e = emalloc(sizeof(Objq));
- e->o = o;
- e->color = Keep;
- *p = e;
- p = &e->next;
+ dprint(1, "init: keep %H\n", o->hash);
+ qput(&objq, o, Keep, 0);
unref(o);
}
for(i = 0; i < ntail; i++){
- if(hasheq(&tail[i], &Zhash))
- continue;
if((o = readobject(tail[i])) == nil){
werrstr("read tail %H: %r", tail[i]);
return -1;
@@ -303,35 +250,33 @@
continue;
}
dprint(1, "init: drop %H\n", o->hash);
- e = emalloc(sizeof(Objq));
- e->o = o;
- e->color = Drop;
- *p = e;
- p = &e->next;
+ qput(&objq, o, Drop, 0);
unref(o);
}
dprint(1, "finding twixt commits\n");
- while(q != nil){
- if(oshas(&drop, q->o->hash))
+ while(qpop(&objq, &e)){
+ if(oshas(&drop, e.o->hash))
ncolor = Drop;
- else if(oshas(&keep, q->o->hash))
+ else if(oshas(&keep, e.o->hash))
ncolor = Keep;
else
ncolor = Blank;
- if(ncolor == Drop || ncolor == Keep && q->color == Keep)
- goto next;
- if(ncolor == Keep && q->color == Drop){
- if(repaint(&keep, &drop, q->o) == -1)
+ if(ancestor && pickbest(&objq, &e, ncolor))
+ goto exactlca;
+ if(ncolor == Keep && e.color == Keep || ncolor == Drop)
+ continue;
+ if(ncolor == Keep && e.color == Drop){
+ if(repaint(&objq, &keep, &drop, e.o, e.dist, ancestor) == -1)
goto error;
}else if (ncolor == Blank) {
- dprint(2, "visit: %s %H\n", q->color == Keep ? "keep" : "drop", q->o->hash);
- if(q->color == Keep)
- osadd(&keep, q->o);
+ if(e.color == Keep)
+ osadd(&keep, e.o);
else
- osadd(&drop, q->o);
- for(i = 0; i < q->o->commit->nparent; i++){
- if((c = readobject(q->o->commit->parent[i])) == nil)
+ osadd(&drop, e.o);
+ o = readobject(e.o->hash);
+ for(i = 0; i < o->commit->nparent; i++){
+ if((c = readobject(e.o->commit->parent[i])) == nil)
goto error;
if(c->type != GCommit){
fprint(2, "warning: %H does not point at commit\n", c->hash);
@@ -338,40 +283,82 @@
unref(c);
continue;
}
- dprint(2, "enqueue: %s %H\n", q->color == Keep ? "keep" : "drop", c->hash);
- n = emalloc(sizeof(Objq));
- n->color = q->color;
- n->next = nil;
- n->o = c;
- e->next = n;
- e = n;
+ dprint(2, "\tenqueue: %s %H\n", colors[e.color], c->hash);
+ qput(&objq, c, e.color, e.dist+1);
unref(c);
}
- }else{
- sysfatal("oops");
+ unref(o);
}
-next:
- n = q->next;
- free(q);
- q = n;
}
- *res = eamalloc(keep.nobj, sizeof(Object*));
- *nres = 0;
- for(i = 0; i < keep.sz; i++){
- if(keep.obj[i] != nil && !oshas(&drop, keep.obj[i]->hash)){
- (*res)[*nres] = keep.obj[i];
- (*nres)++;
+exactlca:
+ if(ancestor){
+ dprint(1, "found ancestor\n");
+ if(objq.best == nil){
+ *nres = 0;
+ *res = nil;
+ }else{
+ *nres = 1;
+ *res = eamalloc(1, sizeof(Object*));
+ (*res)[0] = objq.best;
}
+ }else{
+ dprint(1, "found twixt\n");
+ *res = eamalloc(keep.nobj, sizeof(Object*));
+ *nres = 0;
+ for(i = 0; i < keep.sz; i++){
+ if(keep.obj[i] != nil && !oshas(&drop, keep.obj[i]->hash)){
+ (*res)[*nres] = keep.obj[i];
+ (*nres)++;
+ }
+ }
}
osclear(&keep);
osclear(&drop);
return 0;
error:
- for(; q != nil; q = n) {
- n = q->next;
- free(q);
- }
+ dprint(1, "twixt error: %r\n");
+ free(objq.heap);
return -1;
+}
+
+int
+findtwixt(Hash *head, int nhead, Hash *tail, int ntail, Object ***res, int *nres)
+{
+ return paint(head, nhead, tail, ntail, res, nres, 0);
+}
+
+Object*
+ancestor(Object *a, Object *b)
+{
+ Object **o, *r;
+ int n;
+
+ if(paint(&a->hash, 1, &b->hash, 1, &o, &n, 1) == -1 || n == 0)
+ return nil;
+ r = o[0];
+ free(o);
+ return ref(r);
+}
+
+int
+lca(Eval *ev)
+{
+ Object *a, *b, **o;
+ int n;
+
+ if(ev->nstk < 2){
+ werrstr("ancestor needs 2 objects");
+ return -1;
+ }
+ n = 0;
+ b = pop(ev);
+ a = pop(ev);
+ paint(&a->hash, 1, &b->hash, 1, &o, &n, 1);
+ if(n == 0)
+ return -1;
+ push(ev, *o);
+ free(o);
+ return 0;
}
static int
--- a/sys/src/cmd/git/util.c
+++ b/sys/src/cmd/git/util.c
@@ -321,3 +321,74 @@
}
return pct;
}
+
+void
+qinit(Objq *q)
+{
+ memset(q, 0, sizeof(Objq));
+ q->nheap = 0;
+ q->heapsz = 8;
+ q->heap = eamalloc(q->heapsz, sizeof(Qelt));
+}
+
+void
+qclear(Objq *q)
+{
+ free(q->heap);
+}
+
+void
+qput(Objq *q, Object *o, int color, int dist)
+{
+ Qelt t;
+ int i;
+
+ if(q->nheap == q->heapsz){
+ q->heapsz *= 2;
+ q->heap = earealloc(q->heap, q->heapsz, sizeof(Qelt));
+ }
+ q->heap[q->nheap].o = o;
+ q->heap[q->nheap].color = color;
+ q->heap[q->nheap].dist = dist;
+ q->heap[q->nheap].mtime = o->commit->mtime;
+ for(i = q->nheap; i > 0; i = (i-1)/2){
+ if(q->heap[i].mtime < q->heap[(i-1)/2].mtime)
+ break;
+ t = q->heap[i];
+ q->heap[i] = q->heap[(i-1)/2];
+ q->heap[(i-1)/2] = t;
+ }
+ q->nheap++;
+}
+
+int
+qpop(Objq *q, Qelt *e)
+{
+ int i, l, r, m;
+ Qelt t;
+
+ if(q->nheap == 0)
+ return 0;
+ *e = q->heap[0];
+ if(--q->nheap == 0)
+ return 1;
+
+ i = 0;
+ q->heap[0] = q->heap[q->nheap];
+ while(1){
+ m = i;
+ l = 2*i+1;
+ r = 2*i+2;
+ if(l < q->nheap && q->heap[m].mtime < q->heap[l].mtime)
+ m = l;
+ if(r < q->nheap && q->heap[m].mtime < q->heap[r].mtime)
+ m = r;
+ if(m == i)
+ break;
+ t = q->heap[m];
+ q->heap[m] = q->heap[i];
+ q->heap[i] = t;
+ i = m;
+ }
+ return 1;
+}