git/shallow.c

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#include "cache.h"
#include "lockfile.h"
#include "commit.h"
#include "tag.h"
#include "pkt-line.h"
shallow.c: the 8 steps to select new commits for .git/shallow Suppose a fetch or push is requested between two shallow repositories (with no history deepening or shortening). A pack that contains necessary objects is transferred over together with .git/shallow of the sender. The receiver has to determine whether it needs to update .git/shallow if new refs needs new shallow comits. The rule here is avoid updating .git/shallow by default. But we don't want to waste the received pack. If the pack contains two refs, one needs new shallow commits installed in .git/shallow and one does not, we keep the latter and reject/warn about the former. Even if .git/shallow update is allowed, we only add shallow commits strictly necessary for the former ref (remember the sender can send more shallow commits than necessary) and pay attention not to accidentally cut the receiver history short (no history shortening is asked for) So the steps to figure out what ref need what new shallow commits are: 1. Split the sender shallow commit list into "ours" and "theirs" list by has_sha1_file. Those that exist in current repo in "ours", the remaining in "theirs". 2. Check the receiver .git/shallow, remove from "ours" the ones that also exist in .git/shallow. 3. Fetch the new pack. Either install or unpack it. 4. Do has_sha1_file on "theirs" list again. Drop the ones that fail has_sha1_file. Obviously the new pack does not need them. 5. If the pack is kept, remove from "ours" the ones that do not exist in the new pack. 6. Walk the new refs to answer the question "what shallow commits, both ours and theirs, are required in .git/shallow in order to add this ref?". Shallow commits not associated to any refs are removed from their respective list. 7. (*) Check reachability (from the current refs) of all remaining commits in "ours". Those reachable are removed. We do not want to cut any part of our (reachable) history. We only check up commits. True reachability test is done by check_everything_connected() at the end as usual. 8. Combine the final "ours" and "theirs" and add them all to .git/shallow. Install new refs. The case where some hook rejects some refs on a push is explained in more detail in the push patches. Of these steps, #6 and #7 are expensive. Both require walking through some commits, or in the worst case all commits. And we rather avoid them in at least common case, where the transferred pack does not contain any shallow commits that the sender advertises. Let's look at each scenario: 1) the sender has longer history than the receiver All shallow commits from the sender will be put into "theirs" list at step 1 because none of them exists in current repo. In the common case, "theirs" becomes empty at step 4 and exit early. 2) the sender has shorter history than the receiver All shallow commits from the sender are likely in "ours" list at step 1. In the common case, if the new pack is kept, we could empty "ours" and exit early at step 5. If the pack is not kept, we hit the expensive step 6 then exit after "ours" is emptied. There'll be only a handful of objects to walk in fast-forward case. If it's forced update, we may need to walk to the bottom. 3) the sender has same .git/shallow as the receiver This is similar to case 2 except that "ours" should be emptied at step 2 and exit early. A fetch after "clone --depth=X" is case 1. A fetch after "clone" (from a shallow repo) is case 3. Luckily they're cheap for the common case. A push from "clone --depth=X" falls into case 2, which is expensive. Some more work may be done at the sender/client side to avoid more work on the server side: if the transferred pack does not contain any shallow commits, send-pack should not send any shallow commits to the receive-pack, effectively turning it into a normal push and avoid all steps. This patch implements all steps except #3, already handled by fetch-pack and receive-pack, #6 and #7, which has their own patch due to their size. (*) in previous versions step 7 was put before step 3. I reorder it so that the common case that keeps the pack does not need to walk commits at all. In future if we implement faster commit reachability check (maybe with the help of pack bitmaps or commit cache), step 7 could become cheap and be moved up before 6 again. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-05 13:02:35 +00:00
#include "remote.h"
#include "refs.h"
#include "sha1-array.h"
#include "diff.h"
#include "revision.h"
#include "commit-slab.h"
#include "sigchain.h"
static int is_shallow = -1;
static struct stat_validity shallow_stat;
static char *alternate_shallow_file;
void set_alternate_shallow_file(const char *path, int override)
{
if (is_shallow != -1)
die("BUG: is_repository_shallow must not be called before set_alternate_shallow_file");
if (alternate_shallow_file && !override)
return;
free(alternate_shallow_file);
alternate_shallow_file = path ? xstrdup(path) : NULL;
}
int register_shallow(const unsigned char *sha1)
{
struct commit_graft *graft =
xmalloc(sizeof(struct commit_graft));
struct commit *commit = lookup_commit(sha1);
hashcpy(graft->sha1, sha1);
graft->nr_parent = -1;
if (commit && commit->object.parsed)
commit->parents = NULL;
return register_commit_graft(graft, 0);
}
int is_repository_shallow(void)
{
FILE *fp;
char buf[1024];
const char *path = alternate_shallow_file;
if (is_shallow >= 0)
return is_shallow;
if (!path)
path = git_path("shallow");
/*
* fetch-pack sets '--shallow-file ""' as an indicator that no
* shallow file should be used. We could just open it and it
* will likely fail. But let's do an explicit check instead.
*/
if (!*path || (fp = fopen(path, "r")) == NULL) {
stat_validity_clear(&shallow_stat);
is_shallow = 0;
return is_shallow;
}
stat_validity_update(&shallow_stat, fileno(fp));
is_shallow = 1;
while (fgets(buf, sizeof(buf), fp)) {
unsigned char sha1[20];
if (get_sha1_hex(buf, sha1))
die("bad shallow line: %s", buf);
register_shallow(sha1);
}
fclose(fp);
return is_shallow;
}
struct commit_list *get_shallow_commits(struct object_array *heads, int depth,
int shallow_flag, int not_shallow_flag)
{
int i = 0, cur_depth = 0;
struct commit_list *result = NULL;
struct object_array stack = OBJECT_ARRAY_INIT;
struct commit *commit = NULL;
struct commit_graft *graft;
while (commit || i < heads->nr || stack.nr) {
struct commit_list *p;
if (!commit) {
if (i < heads->nr) {
commit = (struct commit *)
deref_tag(heads->objects[i++].item, NULL, 0);
if (!commit || commit->object.type != OBJ_COMMIT) {
commit = NULL;
continue;
}
if (!commit->util)
commit->util = xmalloc(sizeof(int));
*(int *)commit->util = 0;
cur_depth = 0;
} else {
commit = (struct commit *)
stack.objects[--stack.nr].item;
cur_depth = *(int *)commit->util;
}
}
parse_commit_or_die(commit);
cur_depth++;
if ((depth != INFINITE_DEPTH && cur_depth >= depth) ||
(is_repository_shallow() && !commit->parents &&
(graft = lookup_commit_graft(commit->object.sha1)) != NULL &&
graft->nr_parent < 0)) {
commit_list_insert(commit, &result);
commit->object.flags |= shallow_flag;
commit = NULL;
continue;
}
commit->object.flags |= not_shallow_flag;
for (p = commit->parents, commit = NULL; p; p = p->next) {
if (!p->item->util) {
int *pointer = xmalloc(sizeof(int));
p->item->util = pointer;
*pointer = cur_depth;
} else {
int *pointer = p->item->util;
if (cur_depth >= *pointer)
continue;
*pointer = cur_depth;
}
if (p->next)
add_object_array(&p->item->object,
NULL, &stack);
else {
commit = p->item;
cur_depth = *(int *)commit->util;
}
}
}
return result;
}
void check_shallow_file_for_update(void)
{
if (is_shallow == -1)
die("BUG: shallow must be initialized by now");
if (!stat_validity_check(&shallow_stat, git_path("shallow")))
die("shallow file has changed since we read it");
}
#define SEEN_ONLY 1
#define VERBOSE 2
struct write_shallow_data {
struct strbuf *out;
int use_pack_protocol;
int count;
unsigned flags;
};
static int write_one_shallow(const struct commit_graft *graft, void *cb_data)
{
struct write_shallow_data *data = cb_data;
const char *hex = sha1_to_hex(graft->sha1);
if (graft->nr_parent != -1)
return 0;
if (data->flags & SEEN_ONLY) {
struct commit *c = lookup_commit(graft->sha1);
if (!c || !(c->object.flags & SEEN)) {
if (data->flags & VERBOSE)
printf("Removing %s from .git/shallow\n",
sha1_to_hex(c->object.sha1));
return 0;
}
}
data->count++;
if (data->use_pack_protocol)
packet_buf_write(data->out, "shallow %s", hex);
else {
strbuf_addstr(data->out, hex);
strbuf_addch(data->out, '\n');
}
return 0;
}
static int write_shallow_commits_1(struct strbuf *out, int use_pack_protocol,
const struct sha1_array *extra,
unsigned flags)
{
struct write_shallow_data data;
int i;
data.out = out;
data.use_pack_protocol = use_pack_protocol;
data.count = 0;
data.flags = flags;
for_each_commit_graft(write_one_shallow, &data);
if (!extra)
return data.count;
for (i = 0; i < extra->nr; i++) {
strbuf_addstr(out, sha1_to_hex(extra->sha1[i]));
strbuf_addch(out, '\n');
data.count++;
}
return data.count;
}
int write_shallow_commits(struct strbuf *out, int use_pack_protocol,
const struct sha1_array *extra)
{
return write_shallow_commits_1(out, use_pack_protocol, extra, 0);
}
static struct strbuf temporary_shallow = STRBUF_INIT;
static void remove_temporary_shallow(void)
{
if (temporary_shallow.len) {
unlink_or_warn(temporary_shallow.buf);
strbuf_reset(&temporary_shallow);
}
}
static void remove_temporary_shallow_on_signal(int signo)
{
remove_temporary_shallow();
sigchain_pop(signo);
raise(signo);
}
const char *setup_temporary_shallow(const struct sha1_array *extra)
{
struct strbuf sb = STRBUF_INIT;
int fd;
if (temporary_shallow.len)
die("BUG: attempt to create two temporary shallow files");
if (write_shallow_commits(&sb, 0, extra)) {
strbuf_addstr(&temporary_shallow, git_path("shallow_XXXXXX"));
fd = xmkstemp(temporary_shallow.buf);
atexit(remove_temporary_shallow);
sigchain_push_common(remove_temporary_shallow_on_signal);
if (write_in_full(fd, sb.buf, sb.len) != sb.len)
die_errno("failed to write to %s",
temporary_shallow.buf);
close(fd);
strbuf_release(&sb);
return temporary_shallow.buf;
}
/*
* is_repository_shallow() sees empty string as "no shallow
* file".
*/
return temporary_shallow.buf;
}
void setup_alternate_shallow(struct lock_file *shallow_lock,
const char **alternate_shallow_file,
const struct sha1_array *extra)
{
struct strbuf sb = STRBUF_INIT;
int fd;
fd = hold_lock_file_for_update(shallow_lock, git_path("shallow"),
LOCK_DIE_ON_ERROR);
check_shallow_file_for_update();
if (write_shallow_commits(&sb, 0, extra)) {
if (write_in_full(fd, sb.buf, sb.len) != sb.len)
die_errno("failed to write to %s",
shallow_lock->filename.buf);
*alternate_shallow_file = shallow_lock->filename.buf;
} else
/*
* is_repository_shallow() sees empty string as "no
* shallow file".
*/
*alternate_shallow_file = "";
strbuf_release(&sb);
}
make the sender advertise shallow commits to the receiver If either receive-pack or upload-pack is called on a shallow repository, shallow commits (*) will be sent after the ref advertisement (but before the packet flush), so that the receiver has the full "shape" of the sender's commit graph. This will be needed for the receiver to update its .git/shallow if necessary. This breaks the protocol for all clients trying to push to a shallow repo, or fetch from one. Which is basically the same end result as today's "is_repository_shallow() && die()" in receive-pack and upload-pack. New clients will be made aware of shallow upstream and can make use of this information. The sender must send all shallow commits that are sent in the following pack. It may send more shallow commits than necessary. upload-pack for example may choose to advertise no shallow commits if it knows in advance that the pack it's going to send contains no shallow commits. But upload-pack is the server, so we choose the cheaper way, send full .git/shallow and let the client deal with it. Smart HTTP is not affected by this patch. Shallow support on smart-http comes later separately. (*) A shallow commit is a commit that terminates the revision walker. It is usually put in .git/shallow in order to keep the revision walker from going out of bound because there is no guarantee that objects behind this commit is available. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-05 13:02:32 +00:00
static int advertise_shallow_grafts_cb(const struct commit_graft *graft, void *cb)
{
int fd = *(int *)cb;
if (graft->nr_parent == -1)
packet_write(fd, "shallow %s\n", sha1_to_hex(graft->sha1));
return 0;
}
void advertise_shallow_grafts(int fd)
{
if (!is_repository_shallow())
return;
for_each_commit_graft(advertise_shallow_grafts_cb, &fd);
}
shallow.c: the 8 steps to select new commits for .git/shallow Suppose a fetch or push is requested between two shallow repositories (with no history deepening or shortening). A pack that contains necessary objects is transferred over together with .git/shallow of the sender. The receiver has to determine whether it needs to update .git/shallow if new refs needs new shallow comits. The rule here is avoid updating .git/shallow by default. But we don't want to waste the received pack. If the pack contains two refs, one needs new shallow commits installed in .git/shallow and one does not, we keep the latter and reject/warn about the former. Even if .git/shallow update is allowed, we only add shallow commits strictly necessary for the former ref (remember the sender can send more shallow commits than necessary) and pay attention not to accidentally cut the receiver history short (no history shortening is asked for) So the steps to figure out what ref need what new shallow commits are: 1. Split the sender shallow commit list into "ours" and "theirs" list by has_sha1_file. Those that exist in current repo in "ours", the remaining in "theirs". 2. Check the receiver .git/shallow, remove from "ours" the ones that also exist in .git/shallow. 3. Fetch the new pack. Either install or unpack it. 4. Do has_sha1_file on "theirs" list again. Drop the ones that fail has_sha1_file. Obviously the new pack does not need them. 5. If the pack is kept, remove from "ours" the ones that do not exist in the new pack. 6. Walk the new refs to answer the question "what shallow commits, both ours and theirs, are required in .git/shallow in order to add this ref?". Shallow commits not associated to any refs are removed from their respective list. 7. (*) Check reachability (from the current refs) of all remaining commits in "ours". Those reachable are removed. We do not want to cut any part of our (reachable) history. We only check up commits. True reachability test is done by check_everything_connected() at the end as usual. 8. Combine the final "ours" and "theirs" and add them all to .git/shallow. Install new refs. The case where some hook rejects some refs on a push is explained in more detail in the push patches. Of these steps, #6 and #7 are expensive. Both require walking through some commits, or in the worst case all commits. And we rather avoid them in at least common case, where the transferred pack does not contain any shallow commits that the sender advertises. Let's look at each scenario: 1) the sender has longer history than the receiver All shallow commits from the sender will be put into "theirs" list at step 1 because none of them exists in current repo. In the common case, "theirs" becomes empty at step 4 and exit early. 2) the sender has shorter history than the receiver All shallow commits from the sender are likely in "ours" list at step 1. In the common case, if the new pack is kept, we could empty "ours" and exit early at step 5. If the pack is not kept, we hit the expensive step 6 then exit after "ours" is emptied. There'll be only a handful of objects to walk in fast-forward case. If it's forced update, we may need to walk to the bottom. 3) the sender has same .git/shallow as the receiver This is similar to case 2 except that "ours" should be emptied at step 2 and exit early. A fetch after "clone --depth=X" is case 1. A fetch after "clone" (from a shallow repo) is case 3. Luckily they're cheap for the common case. A push from "clone --depth=X" falls into case 2, which is expensive. Some more work may be done at the sender/client side to avoid more work on the server side: if the transferred pack does not contain any shallow commits, send-pack should not send any shallow commits to the receive-pack, effectively turning it into a normal push and avoid all steps. This patch implements all steps except #3, already handled by fetch-pack and receive-pack, #6 and #7, which has their own patch due to their size. (*) in previous versions step 7 was put before step 3. I reorder it so that the common case that keeps the pack does not need to walk commits at all. In future if we implement faster commit reachability check (maybe with the help of pack bitmaps or commit cache), step 7 could become cheap and be moved up before 6 again. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-05 13:02:35 +00:00
/*
* mark_reachable_objects() should have been run prior to this and all
* reachable commits marked as "SEEN".
*/
void prune_shallow(int show_only)
{
static struct lock_file shallow_lock;
struct strbuf sb = STRBUF_INIT;
int fd;
if (show_only) {
write_shallow_commits_1(&sb, 0, NULL, SEEN_ONLY | VERBOSE);
strbuf_release(&sb);
return;
}
fd = hold_lock_file_for_update(&shallow_lock, git_path("shallow"),
LOCK_DIE_ON_ERROR);
check_shallow_file_for_update();
if (write_shallow_commits_1(&sb, 0, NULL, SEEN_ONLY)) {
if (write_in_full(fd, sb.buf, sb.len) != sb.len)
die_errno("failed to write to %s",
shallow_lock.filename.buf);
commit_lock_file(&shallow_lock);
} else {
unlink(git_path("shallow"));
rollback_lock_file(&shallow_lock);
}
strbuf_release(&sb);
}
struct trace_key trace_shallow = TRACE_KEY_INIT(SHALLOW);
shallow.c: the 8 steps to select new commits for .git/shallow Suppose a fetch or push is requested between two shallow repositories (with no history deepening or shortening). A pack that contains necessary objects is transferred over together with .git/shallow of the sender. The receiver has to determine whether it needs to update .git/shallow if new refs needs new shallow comits. The rule here is avoid updating .git/shallow by default. But we don't want to waste the received pack. If the pack contains two refs, one needs new shallow commits installed in .git/shallow and one does not, we keep the latter and reject/warn about the former. Even if .git/shallow update is allowed, we only add shallow commits strictly necessary for the former ref (remember the sender can send more shallow commits than necessary) and pay attention not to accidentally cut the receiver history short (no history shortening is asked for) So the steps to figure out what ref need what new shallow commits are: 1. Split the sender shallow commit list into "ours" and "theirs" list by has_sha1_file. Those that exist in current repo in "ours", the remaining in "theirs". 2. Check the receiver .git/shallow, remove from "ours" the ones that also exist in .git/shallow. 3. Fetch the new pack. Either install or unpack it. 4. Do has_sha1_file on "theirs" list again. Drop the ones that fail has_sha1_file. Obviously the new pack does not need them. 5. If the pack is kept, remove from "ours" the ones that do not exist in the new pack. 6. Walk the new refs to answer the question "what shallow commits, both ours and theirs, are required in .git/shallow in order to add this ref?". Shallow commits not associated to any refs are removed from their respective list. 7. (*) Check reachability (from the current refs) of all remaining commits in "ours". Those reachable are removed. We do not want to cut any part of our (reachable) history. We only check up commits. True reachability test is done by check_everything_connected() at the end as usual. 8. Combine the final "ours" and "theirs" and add them all to .git/shallow. Install new refs. The case where some hook rejects some refs on a push is explained in more detail in the push patches. Of these steps, #6 and #7 are expensive. Both require walking through some commits, or in the worst case all commits. And we rather avoid them in at least common case, where the transferred pack does not contain any shallow commits that the sender advertises. Let's look at each scenario: 1) the sender has longer history than the receiver All shallow commits from the sender will be put into "theirs" list at step 1 because none of them exists in current repo. In the common case, "theirs" becomes empty at step 4 and exit early. 2) the sender has shorter history than the receiver All shallow commits from the sender are likely in "ours" list at step 1. In the common case, if the new pack is kept, we could empty "ours" and exit early at step 5. If the pack is not kept, we hit the expensive step 6 then exit after "ours" is emptied. There'll be only a handful of objects to walk in fast-forward case. If it's forced update, we may need to walk to the bottom. 3) the sender has same .git/shallow as the receiver This is similar to case 2 except that "ours" should be emptied at step 2 and exit early. A fetch after "clone --depth=X" is case 1. A fetch after "clone" (from a shallow repo) is case 3. Luckily they're cheap for the common case. A push from "clone --depth=X" falls into case 2, which is expensive. Some more work may be done at the sender/client side to avoid more work on the server side: if the transferred pack does not contain any shallow commits, send-pack should not send any shallow commits to the receive-pack, effectively turning it into a normal push and avoid all steps. This patch implements all steps except #3, already handled by fetch-pack and receive-pack, #6 and #7, which has their own patch due to their size. (*) in previous versions step 7 was put before step 3. I reorder it so that the common case that keeps the pack does not need to walk commits at all. In future if we implement faster commit reachability check (maybe with the help of pack bitmaps or commit cache), step 7 could become cheap and be moved up before 6 again. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-05 13:02:35 +00:00
/*
* Step 1, split sender shallow commits into "ours" and "theirs"
* Step 2, clean "ours" based on .git/shallow
*/
void prepare_shallow_info(struct shallow_info *info, struct sha1_array *sa)
{
int i;
trace_printf_key(&trace_shallow, "shallow: prepare_shallow_info\n");
shallow.c: the 8 steps to select new commits for .git/shallow Suppose a fetch or push is requested between two shallow repositories (with no history deepening or shortening). A pack that contains necessary objects is transferred over together with .git/shallow of the sender. The receiver has to determine whether it needs to update .git/shallow if new refs needs new shallow comits. The rule here is avoid updating .git/shallow by default. But we don't want to waste the received pack. If the pack contains two refs, one needs new shallow commits installed in .git/shallow and one does not, we keep the latter and reject/warn about the former. Even if .git/shallow update is allowed, we only add shallow commits strictly necessary for the former ref (remember the sender can send more shallow commits than necessary) and pay attention not to accidentally cut the receiver history short (no history shortening is asked for) So the steps to figure out what ref need what new shallow commits are: 1. Split the sender shallow commit list into "ours" and "theirs" list by has_sha1_file. Those that exist in current repo in "ours", the remaining in "theirs". 2. Check the receiver .git/shallow, remove from "ours" the ones that also exist in .git/shallow. 3. Fetch the new pack. Either install or unpack it. 4. Do has_sha1_file on "theirs" list again. Drop the ones that fail has_sha1_file. Obviously the new pack does not need them. 5. If the pack is kept, remove from "ours" the ones that do not exist in the new pack. 6. Walk the new refs to answer the question "what shallow commits, both ours and theirs, are required in .git/shallow in order to add this ref?". Shallow commits not associated to any refs are removed from their respective list. 7. (*) Check reachability (from the current refs) of all remaining commits in "ours". Those reachable are removed. We do not want to cut any part of our (reachable) history. We only check up commits. True reachability test is done by check_everything_connected() at the end as usual. 8. Combine the final "ours" and "theirs" and add them all to .git/shallow. Install new refs. The case where some hook rejects some refs on a push is explained in more detail in the push patches. Of these steps, #6 and #7 are expensive. Both require walking through some commits, or in the worst case all commits. And we rather avoid them in at least common case, where the transferred pack does not contain any shallow commits that the sender advertises. Let's look at each scenario: 1) the sender has longer history than the receiver All shallow commits from the sender will be put into "theirs" list at step 1 because none of them exists in current repo. In the common case, "theirs" becomes empty at step 4 and exit early. 2) the sender has shorter history than the receiver All shallow commits from the sender are likely in "ours" list at step 1. In the common case, if the new pack is kept, we could empty "ours" and exit early at step 5. If the pack is not kept, we hit the expensive step 6 then exit after "ours" is emptied. There'll be only a handful of objects to walk in fast-forward case. If it's forced update, we may need to walk to the bottom. 3) the sender has same .git/shallow as the receiver This is similar to case 2 except that "ours" should be emptied at step 2 and exit early. A fetch after "clone --depth=X" is case 1. A fetch after "clone" (from a shallow repo) is case 3. Luckily they're cheap for the common case. A push from "clone --depth=X" falls into case 2, which is expensive. Some more work may be done at the sender/client side to avoid more work on the server side: if the transferred pack does not contain any shallow commits, send-pack should not send any shallow commits to the receive-pack, effectively turning it into a normal push and avoid all steps. This patch implements all steps except #3, already handled by fetch-pack and receive-pack, #6 and #7, which has their own patch due to their size. (*) in previous versions step 7 was put before step 3. I reorder it so that the common case that keeps the pack does not need to walk commits at all. In future if we implement faster commit reachability check (maybe with the help of pack bitmaps or commit cache), step 7 could become cheap and be moved up before 6 again. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-05 13:02:35 +00:00
memset(info, 0, sizeof(*info));
info->shallow = sa;
if (!sa)
return;
info->ours = xmalloc(sizeof(*info->ours) * sa->nr);
info->theirs = xmalloc(sizeof(*info->theirs) * sa->nr);
for (i = 0; i < sa->nr; i++) {
if (has_sha1_file(sa->sha1[i])) {
struct commit_graft *graft;
graft = lookup_commit_graft(sa->sha1[i]);
if (graft && graft->nr_parent < 0)
continue;
info->ours[info->nr_ours++] = i;
} else
info->theirs[info->nr_theirs++] = i;
}
}
void clear_shallow_info(struct shallow_info *info)
{
free(info->ours);
free(info->theirs);
}
/* Step 4, remove non-existent ones in "theirs" after getting the pack */
void remove_nonexistent_theirs_shallow(struct shallow_info *info)
{
unsigned char (*sha1)[20] = info->shallow->sha1;
int i, dst;
trace_printf_key(&trace_shallow, "shallow: remove_nonexistent_theirs_shallow\n");
shallow.c: the 8 steps to select new commits for .git/shallow Suppose a fetch or push is requested between two shallow repositories (with no history deepening or shortening). A pack that contains necessary objects is transferred over together with .git/shallow of the sender. The receiver has to determine whether it needs to update .git/shallow if new refs needs new shallow comits. The rule here is avoid updating .git/shallow by default. But we don't want to waste the received pack. If the pack contains two refs, one needs new shallow commits installed in .git/shallow and one does not, we keep the latter and reject/warn about the former. Even if .git/shallow update is allowed, we only add shallow commits strictly necessary for the former ref (remember the sender can send more shallow commits than necessary) and pay attention not to accidentally cut the receiver history short (no history shortening is asked for) So the steps to figure out what ref need what new shallow commits are: 1. Split the sender shallow commit list into "ours" and "theirs" list by has_sha1_file. Those that exist in current repo in "ours", the remaining in "theirs". 2. Check the receiver .git/shallow, remove from "ours" the ones that also exist in .git/shallow. 3. Fetch the new pack. Either install or unpack it. 4. Do has_sha1_file on "theirs" list again. Drop the ones that fail has_sha1_file. Obviously the new pack does not need them. 5. If the pack is kept, remove from "ours" the ones that do not exist in the new pack. 6. Walk the new refs to answer the question "what shallow commits, both ours and theirs, are required in .git/shallow in order to add this ref?". Shallow commits not associated to any refs are removed from their respective list. 7. (*) Check reachability (from the current refs) of all remaining commits in "ours". Those reachable are removed. We do not want to cut any part of our (reachable) history. We only check up commits. True reachability test is done by check_everything_connected() at the end as usual. 8. Combine the final "ours" and "theirs" and add them all to .git/shallow. Install new refs. The case where some hook rejects some refs on a push is explained in more detail in the push patches. Of these steps, #6 and #7 are expensive. Both require walking through some commits, or in the worst case all commits. And we rather avoid them in at least common case, where the transferred pack does not contain any shallow commits that the sender advertises. Let's look at each scenario: 1) the sender has longer history than the receiver All shallow commits from the sender will be put into "theirs" list at step 1 because none of them exists in current repo. In the common case, "theirs" becomes empty at step 4 and exit early. 2) the sender has shorter history than the receiver All shallow commits from the sender are likely in "ours" list at step 1. In the common case, if the new pack is kept, we could empty "ours" and exit early at step 5. If the pack is not kept, we hit the expensive step 6 then exit after "ours" is emptied. There'll be only a handful of objects to walk in fast-forward case. If it's forced update, we may need to walk to the bottom. 3) the sender has same .git/shallow as the receiver This is similar to case 2 except that "ours" should be emptied at step 2 and exit early. A fetch after "clone --depth=X" is case 1. A fetch after "clone" (from a shallow repo) is case 3. Luckily they're cheap for the common case. A push from "clone --depth=X" falls into case 2, which is expensive. Some more work may be done at the sender/client side to avoid more work on the server side: if the transferred pack does not contain any shallow commits, send-pack should not send any shallow commits to the receive-pack, effectively turning it into a normal push and avoid all steps. This patch implements all steps except #3, already handled by fetch-pack and receive-pack, #6 and #7, which has their own patch due to their size. (*) in previous versions step 7 was put before step 3. I reorder it so that the common case that keeps the pack does not need to walk commits at all. In future if we implement faster commit reachability check (maybe with the help of pack bitmaps or commit cache), step 7 could become cheap and be moved up before 6 again. Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-12-05 13:02:35 +00:00
for (i = dst = 0; i < info->nr_theirs; i++) {
if (i != dst)
info->theirs[dst] = info->theirs[i];
if (has_sha1_file(sha1[info->theirs[i]]))
dst++;
}
info->nr_theirs = dst;
}
define_commit_slab(ref_bitmap, uint32_t *);
struct paint_info {
struct ref_bitmap ref_bitmap;
unsigned nr_bits;
char **slab;
char *free, *end;
unsigned slab_count;
};
static uint32_t *paint_alloc(struct paint_info *info)
{
unsigned nr = (info->nr_bits + 31) / 32;
unsigned size = nr * sizeof(uint32_t);
void *p;
if (!info->slab_count || info->free + size > info->end) {
info->slab_count++;
REALLOC_ARRAY(info->slab, info->slab_count);
info->free = xmalloc(COMMIT_SLAB_SIZE);
info->slab[info->slab_count - 1] = info->free;
info->end = info->free + COMMIT_SLAB_SIZE;
}
p = info->free;
info->free += size;
return p;
}
/*
* Given a commit SHA-1, walk down to parents until either SEEN,
* UNINTERESTING or BOTTOM is hit. Set the id-th bit in ref_bitmap for
* all walked commits.
*/
static void paint_down(struct paint_info *info, const unsigned char *sha1,
int id)
{
unsigned int i, nr;
struct commit_list *head = NULL;
int bitmap_nr = (info->nr_bits + 31) / 32;
int bitmap_size = bitmap_nr * sizeof(uint32_t);
uint32_t *tmp = xmalloc(bitmap_size); /* to be freed before return */
uint32_t *bitmap = paint_alloc(info);
struct commit *c = lookup_commit_reference_gently(sha1, 1);
if (!c)
return;
memset(bitmap, 0, bitmap_size);
bitmap[id / 32] |= (1 << (id % 32));
commit_list_insert(c, &head);
while (head) {
struct commit_list *p;
struct commit *c = head->item;
uint32_t **refs = ref_bitmap_at(&info->ref_bitmap, c);
p = head;
head = head->next;
free(p);
/* XXX check "UNINTERESTING" from pack bitmaps if available */
if (c->object.flags & (SEEN | UNINTERESTING))
continue;
else
c->object.flags |= SEEN;
if (*refs == NULL)
*refs = bitmap;
else {
memcpy(tmp, *refs, bitmap_size);
for (i = 0; i < bitmap_nr; i++)
tmp[i] |= bitmap[i];
if (memcmp(tmp, *refs, bitmap_size)) {
*refs = paint_alloc(info);
memcpy(*refs, tmp, bitmap_size);
}
}
if (c->object.flags & BOTTOM)
continue;
if (parse_commit(c))
die("unable to parse commit %s",
sha1_to_hex(c->object.sha1));
for (p = c->parents; p; p = p->next) {
uint32_t **p_refs = ref_bitmap_at(&info->ref_bitmap,
p->item);
if (p->item->object.flags & SEEN)
continue;
if (*p_refs == NULL || *p_refs == *refs)
*p_refs = *refs;
commit_list_insert(p->item, &head);
}
}
nr = get_max_object_index();
for (i = 0; i < nr; i++) {
struct object *o = get_indexed_object(i);
if (o && o->type == OBJ_COMMIT)
o->flags &= ~SEEN;
}
free(tmp);
}
static int mark_uninteresting(const char *refname,
const unsigned char *sha1,
int flags, void *cb_data)
{
struct commit *commit = lookup_commit_reference_gently(sha1, 1);
if (!commit)
return 0;
commit->object.flags |= UNINTERESTING;
mark_parents_uninteresting(commit);
return 0;
}
static void post_assign_shallow(struct shallow_info *info,
struct ref_bitmap *ref_bitmap,
int *ref_status);
/*
* Step 6(+7), associate shallow commits with new refs
*
* info->ref must be initialized before calling this function.
*
* If used is not NULL, it's an array of info->shallow->nr
* bitmaps. The n-th bit set in the m-th bitmap if ref[n] needs the
* m-th shallow commit from info->shallow.
*
* If used is NULL, "ours" and "theirs" are updated. And if ref_status
* is not NULL it's an array of ref->nr ints. ref_status[i] is true if
* the ref needs some shallow commits from either info->ours or
* info->theirs.
*/
void assign_shallow_commits_to_refs(struct shallow_info *info,
uint32_t **used, int *ref_status)
{
unsigned char (*sha1)[20] = info->shallow->sha1;
struct sha1_array *ref = info->ref;
unsigned int i, nr;
int *shallow, nr_shallow = 0;
struct paint_info pi;
trace_printf_key(&trace_shallow, "shallow: assign_shallow_commits_to_refs\n");
shallow = xmalloc(sizeof(*shallow) * (info->nr_ours + info->nr_theirs));
for (i = 0; i < info->nr_ours; i++)
shallow[nr_shallow++] = info->ours[i];
for (i = 0; i < info->nr_theirs; i++)
shallow[nr_shallow++] = info->theirs[i];
/*
* Prepare the commit graph to track what refs can reach what
* (new) shallow commits.
*/
nr = get_max_object_index();
for (i = 0; i < nr; i++) {
struct object *o = get_indexed_object(i);
if (!o || o->type != OBJ_COMMIT)
continue;
o->flags &= ~(UNINTERESTING | BOTTOM | SEEN);
}
memset(&pi, 0, sizeof(pi));
init_ref_bitmap(&pi.ref_bitmap);
pi.nr_bits = ref->nr;
/*
* "--not --all" to cut short the traversal if new refs
* connect to old refs. If not (e.g. force ref updates) it'll
* have to go down to the current shallow commits.
*/
head_ref(mark_uninteresting, NULL);
for_each_ref(mark_uninteresting, NULL);
/* Mark potential bottoms so we won't go out of bound */
for (i = 0; i < nr_shallow; i++) {
struct commit *c = lookup_commit(sha1[shallow[i]]);
c->object.flags |= BOTTOM;
}
for (i = 0; i < ref->nr; i++)
paint_down(&pi, ref->sha1[i], i);
if (used) {
int bitmap_size = ((pi.nr_bits + 31) / 32) * sizeof(uint32_t);
memset(used, 0, sizeof(*used) * info->shallow->nr);
for (i = 0; i < nr_shallow; i++) {
const struct commit *c = lookup_commit(sha1[shallow[i]]);
uint32_t **map = ref_bitmap_at(&pi.ref_bitmap, c);
if (*map)
used[shallow[i]] = xmemdupz(*map, bitmap_size);
}
/*
* unreachable shallow commits are not removed from
* "ours" and "theirs". The user is supposed to run
* step 7 on every ref separately and not trust "ours"
* and "theirs" any more.
*/
} else
post_assign_shallow(info, &pi.ref_bitmap, ref_status);
clear_ref_bitmap(&pi.ref_bitmap);
for (i = 0; i < pi.slab_count; i++)
free(pi.slab[i]);
free(pi.slab);
free(shallow);
}
struct commit_array {
struct commit **commits;
int nr, alloc;
};
static int add_ref(const char *refname,
const unsigned char *sha1, int flags, void *cb_data)
{
struct commit_array *ca = cb_data;
ALLOC_GROW(ca->commits, ca->nr + 1, ca->alloc);
ca->commits[ca->nr] = lookup_commit_reference_gently(sha1, 1);
if (ca->commits[ca->nr])
ca->nr++;
return 0;
}
static void update_refstatus(int *ref_status, int nr, uint32_t *bitmap)
{
int i;
if (!ref_status)
return;
for (i = 0; i < nr; i++)
if (bitmap[i / 32] & (1 << (i % 32)))
ref_status[i]++;
}
/*
* Step 7, reachability test on "ours" at commit level
*/
static void post_assign_shallow(struct shallow_info *info,
struct ref_bitmap *ref_bitmap,
int *ref_status)
{
unsigned char (*sha1)[20] = info->shallow->sha1;
struct commit *c;
uint32_t **bitmap;
int dst, i, j;
int bitmap_nr = (info->ref->nr + 31) / 32;
struct commit_array ca;
trace_printf_key(&trace_shallow, "shallow: post_assign_shallow\n");
if (ref_status)
memset(ref_status, 0, sizeof(*ref_status) * info->ref->nr);
/* Remove unreachable shallow commits from "theirs" */
for (i = dst = 0; i < info->nr_theirs; i++) {
if (i != dst)
info->theirs[dst] = info->theirs[i];
c = lookup_commit(sha1[info->theirs[i]]);
bitmap = ref_bitmap_at(ref_bitmap, c);
if (!*bitmap)
continue;
for (j = 0; j < bitmap_nr; j++)
if (bitmap[0][j]) {
update_refstatus(ref_status, info->ref->nr, *bitmap);
dst++;
break;
}
}
info->nr_theirs = dst;
memset(&ca, 0, sizeof(ca));
head_ref(add_ref, &ca);
for_each_ref(add_ref, &ca);
/* Remove unreachable shallow commits from "ours" */
for (i = dst = 0; i < info->nr_ours; i++) {
if (i != dst)
info->ours[dst] = info->ours[i];
c = lookup_commit(sha1[info->ours[i]]);
bitmap = ref_bitmap_at(ref_bitmap, c);
if (!*bitmap)
continue;
for (j = 0; j < bitmap_nr; j++)
if (bitmap[0][j] &&
/* Step 7, reachability test at commit level */
!in_merge_bases_many(c, ca.nr, ca.commits)) {
update_refstatus(ref_status, info->ref->nr, *bitmap);
dst++;
break;
}
}
info->nr_ours = dst;
free(ca.commits);
}
/* (Delayed) step 7, reachability test at commit level */
int delayed_reachability_test(struct shallow_info *si, int c)
{
if (si->need_reachability_test[c]) {
struct commit *commit = lookup_commit(si->shallow->sha1[c]);
if (!si->commits) {
struct commit_array ca;
memset(&ca, 0, sizeof(ca));
head_ref(add_ref, &ca);
for_each_ref(add_ref, &ca);
si->commits = ca.commits;
si->nr_commits = ca.nr;
}
si->reachable[c] = in_merge_bases_many(commit,
si->nr_commits,
si->commits);
si->need_reachability_test[c] = 0;
}
return si->reachable[c];
}