Merge branch 'jt/fetch-negotiator-skipping'
Add a server-side knob to skip commits in exponential/fibbonacci stride in an attempt to cover wider swath of history with a smaller number of iterations, potentially accepting a larger packfile transfer, instead of going back one commit a time during common ancestor discovery during the "git fetch" transaction. * jt/fetch-negotiator-skipping: negotiator/skipping: skip commits during fetch
This commit is contained in:
Junio C Hamano
250
negotiator/skipping.c
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250
negotiator/skipping.c
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#include "cache.h"
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#include "skipping.h"
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#include "../commit.h"
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#include "../fetch-negotiator.h"
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#include "../prio-queue.h"
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#include "../refs.h"
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#include "../tag.h"
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/* Remember to update object flag allocation in object.h */
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/*
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* Both us and the server know that both parties have this object.
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*/
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#define COMMON (1U << 2)
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/*
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* The server has told us that it has this object. We still need to tell the
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* server that we have this object (or one of its descendants), but since we are
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* going to do that, we do not need to tell the server about its ancestors.
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*/
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#define ADVERTISED (1U << 3)
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/*
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* This commit has entered the priority queue.
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*/
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#define SEEN (1U << 4)
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/*
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* This commit has left the priority queue.
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*/
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#define POPPED (1U << 5)
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static int marked;
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/*
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* An entry in the priority queue.
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*/
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struct entry {
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struct commit *commit;
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/*
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* Used only if commit is not COMMON.
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*/
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uint16_t original_ttl;
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uint16_t ttl;
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};
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struct data {
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struct prio_queue rev_list;
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/*
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* The number of non-COMMON commits in rev_list.
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*/
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int non_common_revs;
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};
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static int compare(const void *a_, const void *b_, void *unused)
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{
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const struct entry *a = a_;
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const struct entry *b = b_;
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return compare_commits_by_commit_date(a->commit, b->commit, NULL);
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}
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static struct entry *rev_list_push(struct data *data, struct commit *commit, int mark)
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{
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struct entry *entry;
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commit->object.flags |= mark | SEEN;
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entry = xcalloc(1, sizeof(*entry));
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entry->commit = commit;
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prio_queue_put(&data->rev_list, entry);
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if (!(mark & COMMON))
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data->non_common_revs++;
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return entry;
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}
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static int clear_marks(const char *refname, const struct object_id *oid,
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int flag, void *cb_data)
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{
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struct object *o = deref_tag(the_repository, parse_object(the_repository, oid), refname, 0);
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if (o && o->type == OBJ_COMMIT)
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clear_commit_marks((struct commit *)o,
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COMMON | ADVERTISED | SEEN | POPPED);
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return 0;
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}
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/*
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* Mark this SEEN commit and all its SEEN ancestors as COMMON.
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*/
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static void mark_common(struct data *data, struct commit *c)
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{
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struct commit_list *p;
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if (c->object.flags & COMMON)
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return;
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c->object.flags |= COMMON;
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if (!(c->object.flags & POPPED))
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data->non_common_revs--;
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if (!c->object.parsed)
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return;
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for (p = c->parents; p; p = p->next) {
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if (p->item->object.flags & SEEN)
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mark_common(data, p->item);
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}
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}
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/*
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* Ensure that the priority queue has an entry for to_push, and ensure that the
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* entry has the correct flags and ttl.
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*
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* This function returns 1 if an entry was found or created, and 0 otherwise
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* (because the entry for this commit had already been popped).
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*/
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static int push_parent(struct data *data, struct entry *entry,
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struct commit *to_push)
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{
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struct entry *parent_entry;
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if (to_push->object.flags & SEEN) {
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int i;
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if (to_push->object.flags & POPPED)
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/*
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* The entry for this commit has already been popped,
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* due to clock skew. Pretend that this parent does not
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* exist.
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*/
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return 0;
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/*
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* Find the existing entry and use it.
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*/
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for (i = 0; i < data->rev_list.nr; i++) {
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parent_entry = data->rev_list.array[i].data;
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if (parent_entry->commit == to_push)
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goto parent_found;
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}
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BUG("missing parent in priority queue");
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parent_found:
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;
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} else {
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parent_entry = rev_list_push(data, to_push, 0);
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}
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if (entry->commit->object.flags & (COMMON | ADVERTISED)) {
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mark_common(data, to_push);
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} else {
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uint16_t new_original_ttl = entry->ttl
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? entry->original_ttl : entry->original_ttl * 3 / 2 + 1;
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uint16_t new_ttl = entry->ttl
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? entry->ttl - 1 : new_original_ttl;
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if (parent_entry->original_ttl < new_original_ttl) {
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parent_entry->original_ttl = new_original_ttl;
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parent_entry->ttl = new_ttl;
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}
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}
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return 1;
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}
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static const struct object_id *get_rev(struct data *data)
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{
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struct commit *to_send = NULL;
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while (to_send == NULL) {
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struct entry *entry;
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struct commit *commit;
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struct commit_list *p;
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int parent_pushed = 0;
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if (data->rev_list.nr == 0 || data->non_common_revs == 0)
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return NULL;
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entry = prio_queue_get(&data->rev_list);
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commit = entry->commit;
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commit->object.flags |= POPPED;
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if (!(commit->object.flags & COMMON))
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data->non_common_revs--;
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if (!(commit->object.flags & COMMON) && !entry->ttl)
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to_send = commit;
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parse_commit(commit);
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for (p = commit->parents; p; p = p->next)
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parent_pushed |= push_parent(data, entry, p->item);
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if (!(commit->object.flags & COMMON) && !parent_pushed)
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/*
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* This commit has no parents, or all of its parents
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* have already been popped (due to clock skew), so send
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* it anyway.
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*/
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to_send = commit;
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free(entry);
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}
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return &to_send->object.oid;
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}
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static void known_common(struct fetch_negotiator *n, struct commit *c)
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{
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if (c->object.flags & SEEN)
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return;
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rev_list_push(n->data, c, ADVERTISED);
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}
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static void add_tip(struct fetch_negotiator *n, struct commit *c)
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{
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n->known_common = NULL;
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if (c->object.flags & SEEN)
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return;
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rev_list_push(n->data, c, 0);
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}
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static const struct object_id *next(struct fetch_negotiator *n)
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{
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n->known_common = NULL;
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n->add_tip = NULL;
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return get_rev(n->data);
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}
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static int ack(struct fetch_negotiator *n, struct commit *c)
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{
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int known_to_be_common = !!(c->object.flags & COMMON);
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if (!(c->object.flags & SEEN))
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die("received ack for commit %s not sent as 'have'\n",
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oid_to_hex(&c->object.oid));
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mark_common(n->data, c);
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return known_to_be_common;
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}
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static void release(struct fetch_negotiator *n)
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{
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clear_prio_queue(&((struct data *)n->data)->rev_list);
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FREE_AND_NULL(n->data);
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}
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void skipping_negotiator_init(struct fetch_negotiator *negotiator)
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{
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struct data *data;
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negotiator->known_common = known_common;
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negotiator->add_tip = add_tip;
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negotiator->next = next;
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negotiator->ack = ack;
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negotiator->release = release;
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negotiator->data = data = xcalloc(1, sizeof(*data));
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data->rev_list.compare = compare;
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if (marked)
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for_each_ref(clear_marks, NULL);
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marked = 1;
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}
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