git/builtin-rev-list.c
Junio C Hamano b9849a1ab6 Make sure quickfetch is not fooled with a previous, incomplete fetch.
This updates git-rev-list --objects to be a bit more careful
when listing a blob object to make sure the blob actually
exists, and uses it to make sure the quick-fetch optimization we
introduced earlier is not fooled by a previous incomplete fetch.

The quick-fetch optimization works by running this command:

	git rev-list --objects <<commit-list>> --not --all

where <<commit-list>> is a list of commits that we are going to
fetch from the other side.  If there is any object missing to
complete the <<commit-list>>, the rev-list would fail and die
(say, the commit was in our repository, but its tree wasn't --
then it will barf while trying to list the blobs the tree
contains because it cannot read that tree).

Usually we do not have the objects (otherwise why would we
fetching?), but in one important special case we do: when the
remote repository is used as an alternate object store
(i.e. pointed by .git/objects/info/alternates).  We could check
.git/objects/info/alternates to see if the remote we are
interacting with is one of them (or is used as an alternate,
recursively, by one of them), but that check is more cumbersome
than it is worth.

The above check however did not catch missing blob, because
object listing code did not read nor check blob objects, knowing
that blobs do not contain any further references to other
objects.  This commit fixes it with practically unmeasurable
overhead.

I've benched this with

	git rev-list --objects --all >/dev/null

in the kernel repository, with three different implementations
of the "check-blob".

 - Checking with has_sha1_file() has negligible (unmeasurable)
   performance penalty.

 - Checking with sha1_object_info() makes it somewhat slower,
   perhaps by 5%.

 - Checking with read_sha1_file() to cause a fully re-validation
   is prohibitively expensive (about 4 times as much runtime).

In my original patch, I had this as a command line option, but
the overhead is small enough that it is not really worth it.

Signed-off-by: Junio C Hamano <junkio@cox.net>
2007-04-17 00:14:59 -07:00

573 lines
13 KiB
C

#include "cache.h"
#include "refs.h"
#include "tag.h"
#include "commit.h"
#include "tree.h"
#include "blob.h"
#include "tree-walk.h"
#include "diff.h"
#include "revision.h"
#include "list-objects.h"
#include "builtin.h"
/* bits #0-15 in revision.h */
#define COUNTED (1u<<16)
static const char rev_list_usage[] =
"git-rev-list [OPTION] <commit-id>... [ -- paths... ]\n"
" limiting output:\n"
" --max-count=nr\n"
" --max-age=epoch\n"
" --min-age=epoch\n"
" --sparse\n"
" --no-merges\n"
" --remove-empty\n"
" --all\n"
" --stdin\n"
" ordering output:\n"
" --topo-order\n"
" --date-order\n"
" formatting output:\n"
" --parents\n"
" --objects | --objects-edge\n"
" --unpacked\n"
" --header | --pretty\n"
" --abbrev=nr | --no-abbrev\n"
" --abbrev-commit\n"
" --left-right\n"
" special purpose:\n"
" --bisect\n"
" --bisect-vars"
;
static struct rev_info revs;
static int bisect_list;
static int show_timestamp;
static int hdr_termination;
static const char *header_prefix;
static void show_commit(struct commit *commit)
{
if (show_timestamp)
printf("%lu ", commit->date);
if (header_prefix)
fputs(header_prefix, stdout);
if (commit->object.flags & BOUNDARY)
putchar('-');
else if (revs.left_right) {
if (commit->object.flags & SYMMETRIC_LEFT)
putchar('<');
else
putchar('>');
}
if (revs.abbrev_commit && revs.abbrev)
fputs(find_unique_abbrev(commit->object.sha1, revs.abbrev),
stdout);
else
fputs(sha1_to_hex(commit->object.sha1), stdout);
if (revs.parents) {
struct commit_list *parents = commit->parents;
while (parents) {
struct object *o = &(parents->item->object);
parents = parents->next;
if (o->flags & TMP_MARK)
continue;
printf(" %s", sha1_to_hex(o->sha1));
o->flags |= TMP_MARK;
}
/* TMP_MARK is a general purpose flag that can
* be used locally, but the user should clean
* things up after it is done with them.
*/
for (parents = commit->parents;
parents;
parents = parents->next)
parents->item->object.flags &= ~TMP_MARK;
}
if (revs.commit_format == CMIT_FMT_ONELINE)
putchar(' ');
else
putchar('\n');
if (revs.verbose_header) {
static char pretty_header[16384];
pretty_print_commit(revs.commit_format, commit, ~0,
pretty_header, sizeof(pretty_header),
revs.abbrev, NULL, NULL, revs.relative_date);
printf("%s%c", pretty_header, hdr_termination);
}
fflush(stdout);
if (commit->parents) {
free_commit_list(commit->parents);
commit->parents = NULL;
}
free(commit->buffer);
commit->buffer = NULL;
}
static void show_object(struct object_array_entry *p)
{
/* An object with name "foo\n0000000..." can be used to
* confuse downstream git-pack-objects very badly.
*/
const char *ep = strchr(p->name, '\n');
if (p->item->type == OBJ_BLOB && !has_sha1_file(p->item->sha1))
die("missing blob object '%s'", sha1_to_hex(p->item->sha1));
if (ep) {
printf("%s %.*s\n", sha1_to_hex(p->item->sha1),
(int) (ep - p->name),
p->name);
}
else
printf("%s %s\n", sha1_to_hex(p->item->sha1), p->name);
}
static void show_edge(struct commit *commit)
{
printf("-%s\n", sha1_to_hex(commit->object.sha1));
}
/*
* This is a truly stupid algorithm, but it's only
* used for bisection, and we just don't care enough.
*
* We care just barely enough to avoid recursing for
* non-merge entries.
*/
static int count_distance(struct commit_list *entry)
{
int nr = 0;
while (entry) {
struct commit *commit = entry->item;
struct commit_list *p;
if (commit->object.flags & (UNINTERESTING | COUNTED))
break;
if (!revs.prune_fn || (commit->object.flags & TREECHANGE))
nr++;
commit->object.flags |= COUNTED;
p = commit->parents;
entry = p;
if (p) {
p = p->next;
while (p) {
nr += count_distance(p);
p = p->next;
}
}
}
return nr;
}
static void clear_distance(struct commit_list *list)
{
while (list) {
struct commit *commit = list->item;
commit->object.flags &= ~COUNTED;
list = list->next;
}
}
#define DEBUG_BISECT 0
static inline int weight(struct commit_list *elem)
{
return *((int*)(elem->item->util));
}
static inline void weight_set(struct commit_list *elem, int weight)
{
*((int*)(elem->item->util)) = weight;
}
static int count_interesting_parents(struct commit *commit)
{
struct commit_list *p;
int count;
for (count = 0, p = commit->parents; p; p = p->next) {
if (p->item->object.flags & UNINTERESTING)
continue;
count++;
}
return count;
}
static inline int halfway(struct commit_list *p, int distance, int nr)
{
/*
* Don't short-cut something we are not going to return!
*/
if (revs.prune_fn && !(p->item->object.flags & TREECHANGE))
return 0;
if (DEBUG_BISECT)
return 0;
/*
* 2 and 3 are halfway of 5.
* 3 is halfway of 6 but 2 and 4 are not.
*/
distance *= 2;
switch (distance - nr) {
case -1: case 0: case 1:
return 1;
default:
return 0;
}
}
#if !DEBUG_BISECT
#define show_list(a,b,c,d) do { ; } while (0)
#else
static void show_list(const char *debug, int counted, int nr,
struct commit_list *list)
{
struct commit_list *p;
fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);
for (p = list; p; p = p->next) {
struct commit_list *pp;
struct commit *commit = p->item;
unsigned flags = commit->object.flags;
enum object_type type;
unsigned long size;
char *buf = read_sha1_file(commit->object.sha1, &type, &size);
char *ep, *sp;
fprintf(stderr, "%c%c%c ",
(flags & TREECHANGE) ? 'T' : ' ',
(flags & UNINTERESTING) ? 'U' : ' ',
(flags & COUNTED) ? 'C' : ' ');
if (commit->util)
fprintf(stderr, "%3d", weight(p));
else
fprintf(stderr, "---");
fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.sha1));
for (pp = commit->parents; pp; pp = pp->next)
fprintf(stderr, " %.*s", 8,
sha1_to_hex(pp->item->object.sha1));
sp = strstr(buf, "\n\n");
if (sp) {
sp += 2;
for (ep = sp; *ep && *ep != '\n'; ep++)
;
fprintf(stderr, " %.*s", (int)(ep - sp), sp);
}
fprintf(stderr, "\n");
}
}
#endif /* DEBUG_BISECT */
/*
* zero or positive weight is the number of interesting commits it can
* reach, including itself. Especially, weight = 0 means it does not
* reach any tree-changing commits (e.g. just above uninteresting one
* but traversal is with pathspec).
*
* weight = -1 means it has one parent and its distance is yet to
* be computed.
*
* weight = -2 means it has more than one parent and its distance is
* unknown. After running count_distance() first, they will get zero
* or positive distance.
*/
static struct commit_list *find_bisection(struct commit_list *list,
int *reaches, int *all)
{
int n, nr, on_list, counted, distance;
struct commit_list *p, *best, *next, *last;
int *weights;
show_list("bisection 2 entry", 0, 0, list);
/*
* Count the number of total and tree-changing items on the
* list, while reversing the list.
*/
for (nr = on_list = 0, last = NULL, p = list;
p;
p = next) {
unsigned flags = p->item->object.flags;
next = p->next;
if (flags & UNINTERESTING)
continue;
p->next = last;
last = p;
if (!revs.prune_fn || (flags & TREECHANGE))
nr++;
on_list++;
}
list = last;
show_list("bisection 2 sorted", 0, nr, list);
*all = nr;
weights = xcalloc(on_list, sizeof(int*));
counted = 0;
for (n = 0, p = list; p; p = p->next) {
struct commit *commit = p->item;
unsigned flags = commit->object.flags;
p->item->util = &weights[n++];
switch (count_interesting_parents(commit)) {
case 0:
if (!revs.prune_fn || (flags & TREECHANGE)) {
weight_set(p, 1);
counted++;
show_list("bisection 2 count one",
counted, nr, list);
}
/*
* otherwise, it is known not to reach any
* tree-changing commit and gets weight 0.
*/
break;
case 1:
weight_set(p, -1);
break;
default:
weight_set(p, -2);
break;
}
}
show_list("bisection 2 initialize", counted, nr, list);
/*
* If you have only one parent in the resulting set
* then you can reach one commit more than that parent
* can reach. So we do not have to run the expensive
* count_distance() for single strand of pearls.
*
* However, if you have more than one parents, you cannot
* just add their distance and one for yourself, since
* they usually reach the same ancestor and you would
* end up counting them twice that way.
*
* So we will first count distance of merges the usual
* way, and then fill the blanks using cheaper algorithm.
*/
for (p = list; p; p = p->next) {
if (p->item->object.flags & UNINTERESTING)
continue;
n = weight(p);
if (n != -2)
continue;
distance = count_distance(p);
clear_distance(list);
weight_set(p, distance);
/* Does it happen to be at exactly half-way? */
if (halfway(p, distance, nr)) {
p->next = NULL;
*reaches = distance;
free(weights);
return p;
}
counted++;
}
show_list("bisection 2 count_distance", counted, nr, list);
while (counted < nr) {
for (p = list; p; p = p->next) {
struct commit_list *q;
unsigned flags = p->item->object.flags;
if (0 <= weight(p))
continue;
for (q = p->item->parents; q; q = q->next) {
if (q->item->object.flags & UNINTERESTING)
continue;
if (0 <= weight(q))
break;
}
if (!q)
continue;
/*
* weight for p is unknown but q is known.
* add one for p itself if p is to be counted,
* otherwise inherit it from q directly.
*/
if (!revs.prune_fn || (flags & TREECHANGE)) {
weight_set(p, weight(q)+1);
counted++;
show_list("bisection 2 count one",
counted, nr, list);
}
else
weight_set(p, weight(q));
/* Does it happen to be at exactly half-way? */
distance = weight(p);
if (halfway(p, distance, nr)) {
p->next = NULL;
*reaches = distance;
free(weights);
return p;
}
}
}
show_list("bisection 2 counted all", counted, nr, list);
/* Then find the best one */
counted = -1;
best = list;
for (p = list; p; p = p->next) {
unsigned flags = p->item->object.flags;
if (revs.prune_fn && !(flags & TREECHANGE))
continue;
distance = weight(p);
if (nr - distance < distance)
distance = nr - distance;
if (distance > counted) {
best = p;
counted = distance;
*reaches = weight(p);
}
}
if (best)
best->next = NULL;
free(weights);
return best;
}
static void read_revisions_from_stdin(struct rev_info *revs)
{
char line[1000];
while (fgets(line, sizeof(line), stdin) != NULL) {
int len = strlen(line);
if (line[len - 1] == '\n')
line[--len] = 0;
if (!len)
break;
if (line[0] == '-')
die("options not supported in --stdin mode");
if (handle_revision_arg(line, revs, 0, 1))
die("bad revision '%s'", line);
}
}
int cmd_rev_list(int argc, const char **argv, const char *prefix)
{
struct commit_list *list;
int i;
int read_from_stdin = 0;
int bisect_show_vars = 0;
git_config(git_default_config);
init_revisions(&revs, prefix);
revs.abbrev = 0;
revs.commit_format = CMIT_FMT_UNSPECIFIED;
argc = setup_revisions(argc, argv, &revs, NULL);
for (i = 1 ; i < argc; i++) {
const char *arg = argv[i];
if (!strcmp(arg, "--header")) {
revs.verbose_header = 1;
continue;
}
if (!strcmp(arg, "--timestamp")) {
show_timestamp = 1;
continue;
}
if (!strcmp(arg, "--bisect")) {
bisect_list = 1;
continue;
}
if (!strcmp(arg, "--bisect-vars")) {
bisect_list = 1;
bisect_show_vars = 1;
continue;
}
if (!strcmp(arg, "--stdin")) {
if (read_from_stdin++)
die("--stdin given twice?");
read_revisions_from_stdin(&revs);
continue;
}
usage(rev_list_usage);
}
if (revs.commit_format != CMIT_FMT_UNSPECIFIED) {
/* The command line has a --pretty */
hdr_termination = '\n';
if (revs.commit_format == CMIT_FMT_ONELINE)
header_prefix = "";
else
header_prefix = "commit ";
}
else if (revs.verbose_header)
/* Only --header was specified */
revs.commit_format = CMIT_FMT_RAW;
list = revs.commits;
if ((!list &&
(!(revs.tag_objects||revs.tree_objects||revs.blob_objects) &&
!revs.pending.nr)) ||
revs.diff)
usage(rev_list_usage);
save_commit_buffer = revs.verbose_header || revs.grep_filter;
track_object_refs = 0;
if (bisect_list)
revs.limited = 1;
prepare_revision_walk(&revs);
if (revs.tree_objects)
mark_edges_uninteresting(revs.commits, &revs, show_edge);
if (bisect_list) {
int reaches = reaches, all = all;
revs.commits = find_bisection(revs.commits, &reaches, &all);
if (bisect_show_vars) {
int cnt;
if (!revs.commits)
return 1;
/*
* revs.commits can reach "reaches" commits among
* "all" commits. If it is good, then there are
* (all-reaches) commits left to be bisected.
* On the other hand, if it is bad, then the set
* to bisect is "reaches".
* A bisect set of size N has (N-1) commits further
* to test, as we already know one bad one.
*/
cnt = all-reaches;
if (cnt < reaches)
cnt = reaches;
printf("bisect_rev=%s\n"
"bisect_nr=%d\n"
"bisect_good=%d\n"
"bisect_bad=%d\n"
"bisect_all=%d\n",
sha1_to_hex(revs.commits->item->object.sha1),
cnt - 1,
all - reaches - 1,
reaches - 1,
all);
return 0;
}
}
traverse_commit_list(&revs, show_commit, show_object);
return 0;
}