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bisect.c 22.93 KiB
#include "cache.h"
#include "commit.h"
#include "diff.h"
#include "revision.h"
#include "refs.h"
#include "list-objects.h"
#include "quote.h"
#include "sha1-lookup.h"
#include "run-command.h"
#include "log-tree.h"
#include "bisect.h"
#include "sha1-array.h"
#include "argv-array.h"
static struct sha1_array good_revs;
static struct sha1_array skipped_revs;
static const unsigned char *current_bad_sha1;
static const char *argv_checkout[] = {"checkout", "-q", NULL, "--", NULL};
static const char *argv_show_branch[] = {"show-branch", NULL, NULL};
static const char *argv_update_ref[] = {"update-ref", "--no-deref", "BISECT_HEAD", NULL, NULL};
/* bits #0-15 in revision.h */
#define COUNTED (1u<<16)
/*
* 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 (!(commit->object.flags & TREESAME))
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 nr)
{
/*
* Don't short-cut something we are not going to return!
*/
if (p->item->object.flags & TREESAME)
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.
*/
switch (2 * weight(p) - 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);
const char *subject_start;
int subject_len;
fprintf(stderr, "%c%c%c ",
(flags & TREESAME) ? ' ' : '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));
subject_len = find_commit_subject(buf, &subject_start);
if (subject_len)
fprintf(stderr, " %.*s", subject_len, subject_start);
fprintf(stderr, "\n");
}
}
#endif /* DEBUG_BISECT */
static struct commit_list *best_bisection(struct commit_list *list, int nr)
{
struct commit_list *p, *best;
int best_distance = -1;
best = list;
for (p = list; p; p = p->next) {
int distance;
unsigned flags = p->item->object.flags;
if (flags & TREESAME)
continue;
distance = weight(p);
if (nr - distance < distance)
distance = nr - distance;
if (distance > best_distance) {
best = p;
best_distance = distance;
}
}
return best;
}
struct commit_dist {
struct commit *commit;
int distance;
};
static int compare_commit_dist(const void *a_, const void *b_)
{
struct commit_dist *a, *b;
a = (struct commit_dist *)a_;
b = (struct commit_dist *)b_;
if (a->distance != b->distance)
return b->distance - a->distance; /* desc sort */
return hashcmp(a->commit->object.sha1, b->commit->object.sha1);
}
static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
{
struct commit_list *p;
struct commit_dist *array = xcalloc(nr, sizeof(*array));
int cnt, i;
for (p = list, cnt = 0; p; p = p->next) {
int distance;
unsigned flags = p->item->object.flags;
if (flags & TREESAME)
continue;
distance = weight(p); if (nr - distance < distance)
distance = nr - distance;
array[cnt].commit = p->item;
array[cnt].distance = distance;
cnt++;
}
qsort(array, cnt, sizeof(*array), compare_commit_dist);
for (p = list, i = 0; i < cnt; i++) {
struct name_decoration *r = xmalloc(sizeof(*r) + 100);
struct object *obj = &(array[i].commit->object);
sprintf(r->name, "dist=%d", array[i].distance);
r->next = add_decoration(&name_decoration, obj, r);
p->item = array[i].commit;
p = p->next;
}
if (p)
p->next = NULL;
free(array);
return list;
}
/*
* 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 *do_find_bisection(struct commit_list *list,
int nr, int *weights,
int find_all)
{
int n, counted;
struct commit_list *p;
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 (!(flags & TREESAME)) {
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;
if (weight(p) != -2)
continue;
weight_set(p, count_distance(p));
clear_distance(list);
/* Does it happen to be at exactly half-way? */
if (!find_all && halfway(p, nr))
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 (!(flags & TREESAME)) {
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? */
if (!find_all && halfway(p, nr))
return p;
}
}
show_list("bisection 2 counted all", counted, nr, list);
if (!find_all)
return best_bisection(list, nr);
else
return best_bisection_sorted(list, nr);
}
struct commit_list *find_bisection(struct commit_list *list,
int *reaches, int *all,
int find_all)
{
int nr, on_list;
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 (!(flags & TREESAME))
nr++;
on_list++;
}
list = last;
show_list("bisection 2 sorted", 0, nr, list);
*all = nr;
weights = xcalloc(on_list, sizeof(*weights));
/* Do the real work of finding bisection commit. */
best = do_find_bisection(list, nr, weights, find_all);
if (best) {
if (!find_all)
best->next = NULL;
*reaches = weight(best);
}
free(weights);
return best;
}
static int register_ref(const char *refname, const unsigned char *sha1,
int flags, void *cb_data)
{
if (!strcmp(refname, "bad")) {
current_bad_sha1 = sha1;
} else if (!prefixcmp(refname, "good-")) {
sha1_array_append(&good_revs, sha1);
} else if (!prefixcmp(refname, "skip-")) {
sha1_array_append(&skipped_revs, sha1);
}
return 0;
}
static int read_bisect_refs(void)
{
return for_each_ref_in("refs/bisect/", register_ref, NULL);
}
static void read_bisect_paths(struct argv_array *array)
{
struct strbuf str = STRBUF_INIT;
const char *filename = git_path("BISECT_NAMES");
FILE *fp = fopen(filename, "r");
if (!fp)
die_errno("Could not open file '%s'", filename);
while (strbuf_getline(&str, fp, '\n') != EOF) {
strbuf_trim(&str);
if (sq_dequote_to_argv_array(str.buf, array))
die("Badly quoted content in file '%s': %s",
filename, str.buf);
}
strbuf_release(&str);
fclose(fp);
}
static char *join_sha1_array_hex(struct sha1_array *array, char delim)
{
struct strbuf joined_hexs = STRBUF_INIT;
int i;
for (i = 0; i < array->nr; i++) {
strbuf_addstr(&joined_hexs, sha1_to_hex(array->sha1[i]));
if (i + 1 < array->nr)
strbuf_addch(&joined_hexs, delim);
}
return strbuf_detach(&joined_hexs, NULL);
}
/*
* In this function, passing a not NULL skipped_first is very special.
* It means that we want to know if the first commit in the list is
* skipped because we will want to test a commit away from it if it is
* indeed skipped.
* So if the first commit is skipped, we cannot take the shortcut to
* just "return list" when we find the first non skipped commit, we
* have to return a fully filtered list.
*
* We use (*skipped_first == -1) to mean "it has been found that the
* first commit is not skipped". In this case *skipped_first is set back
* to 0 just before the function returns.
*/
struct commit_list *filter_skipped(struct commit_list *list,
struct commit_list **tried,
int show_all,
int *count,
int *skipped_first)
{
struct commit_list *filtered = NULL, **f = &filtered;
*tried = NULL;
if (skipped_first)
*skipped_first = 0;
if (count)
*count = 0;
if (!skipped_revs.nr)
return list;
while (list) {
struct commit_list *next = list->next;
list->next = NULL;
if (0 <= sha1_array_lookup(&skipped_revs, list->item->object.sha1)) {
if (skipped_first && !*skipped_first)
*skipped_first = 1;
/* Move current to tried list */
*tried = list;
tried = &list->next;
} else {
if (!show_all) {
if (!skipped_first || !*skipped_first)
return list;
} else if (skipped_first && !*skipped_first) {
/* This means we know it's not skipped */
*skipped_first = -1;
}
/* Move current to filtered list */
*f = list;
f = &list->next;
if (count)
(*count)++;
}
list = next;
}
if (skipped_first && *skipped_first == -1)
*skipped_first = 0;
return filtered;
}
#define PRN_MODULO 32768
/*
* This is a pseudo random number generator based on "man 3 rand".
* It is not used properly because the seed is the argument and it
* is increased by one between each call, but that should not matter
* for this application.
*/
static int get_prn(int count) {
count = count * 1103515245 + 12345;
return ((unsigned)(count/65536) % PRN_MODULO);
}
/*
* Custom integer square root from
* http://en.wikipedia.org/wiki/Integer_square_root
*/
static int sqrti(int val)
{
float d, x = val;
if (val == 0)
return 0;
do {
float y = (x + (float)val / x) / 2;
d = (y > x) ? y - x : x - y;
x = y;
} while (d >= 0.5);
return (int)x;
}
static struct commit_list *skip_away(struct commit_list *list, int count)
{
struct commit_list *cur, *previous;
int prn, index, i;
prn = get_prn(count);
index = (count * prn / PRN_MODULO) * sqrti(prn) / sqrti(PRN_MODULO);
cur = list;
previous = NULL;
for (i = 0; cur; cur = cur->next, i++) {
if (i == index) {
if (hashcmp(cur->item->object.sha1, current_bad_sha1))
return cur;
if (previous)
return previous;
return list;
}
previous = cur;
}
return list;
}
static struct commit_list *managed_skipped(struct commit_list *list,
struct commit_list **tried)
{
int count, skipped_first;
*tried = NULL;
if (!skipped_revs.nr)
return list;
list = filter_skipped(list, tried, 0, &count, &skipped_first);
if (!skipped_first)
return list;
return skip_away(list, count);
}
static void bisect_rev_setup(struct rev_info *revs, const char *prefix,
const char *bad_format, const char *good_format,
int read_paths)
{
struct argv_array rev_argv = ARGV_ARRAY_INIT;
int i;
init_revisions(revs, prefix);
revs->abbrev = 0;
revs->commit_format = CMIT_FMT_UNSPECIFIED;
/* rev_argv.argv[0] will be ignored by setup_revisions */
argv_array_push(&rev_argv, "bisect_rev_setup");
argv_array_pushf(&rev_argv, bad_format, sha1_to_hex(current_bad_sha1));
for (i = 0; i < good_revs.nr; i++)
argv_array_pushf(&rev_argv, good_format,
sha1_to_hex(good_revs.sha1[i]));
argv_array_push(&rev_argv, "--");
if (read_paths)
read_bisect_paths(&rev_argv);
setup_revisions(rev_argv.argc, rev_argv.argv, revs, NULL);
/* XXX leak rev_argv, as "revs" may still be pointing to it */
}
static void bisect_common(struct rev_info *revs)
{
if (prepare_revision_walk(revs))
die("revision walk setup failed");
if (revs->tree_objects)
mark_edges_uninteresting(revs->commits, revs, NULL);
}
static void exit_if_skipped_commits(struct commit_list *tried,
const unsigned char *bad){
if (!tried)
return;
printf("There are only 'skip'ped commits left to test.\n"
"The first bad commit could be any of:\n");
print_commit_list(tried, "%s\n", "%s\n");
if (bad)
printf("%s\n", sha1_to_hex(bad));
printf("We cannot bisect more!\n");
exit(2);
}
static int is_expected_rev(const unsigned char *sha1)
{
const char *filename = git_path("BISECT_EXPECTED_REV");
struct stat st;
struct strbuf str = STRBUF_INIT;
FILE *fp;
int res = 0;
if (stat(filename, &st) || !S_ISREG(st.st_mode))
return 0;
fp = fopen(filename, "r");
if (!fp)
return 0;
if (strbuf_getline(&str, fp, '\n') != EOF)
res = !strcmp(str.buf, sha1_to_hex(sha1));
strbuf_release(&str);
fclose(fp);
return res;
}
static void mark_expected_rev(char *bisect_rev_hex)
{
int len = strlen(bisect_rev_hex);
const char *filename = git_path("BISECT_EXPECTED_REV");
int fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
if (fd < 0)
die_errno("could not create file '%s'", filename);
bisect_rev_hex[len] = '\n';
write_or_die(fd, bisect_rev_hex, len + 1);
bisect_rev_hex[len] = '\0';
if (close(fd) < 0)
die("closing file %s: %s", filename, strerror(errno));
}
static int bisect_checkout(char *bisect_rev_hex, int no_checkout)
{
int res;
mark_expected_rev(bisect_rev_hex);
argv_checkout[2] = bisect_rev_hex;
if (no_checkout) {
argv_update_ref[3] = bisect_rev_hex;
if (run_command_v_opt(argv_update_ref, RUN_GIT_CMD))
die("update-ref --no-deref HEAD failed on %s",
bisect_rev_hex);
} else {
res = run_command_v_opt(argv_checkout, RUN_GIT_CMD);
if (res)
exit(res); }
argv_show_branch[1] = bisect_rev_hex;
return run_command_v_opt(argv_show_branch, RUN_GIT_CMD);
}
static struct commit *get_commit_reference(const unsigned char *sha1)
{
struct commit *r = lookup_commit_reference(sha1);
if (!r)
die("Not a valid commit name %s", sha1_to_hex(sha1));
return r;
}
static struct commit **get_bad_and_good_commits(int *rev_nr)
{
int len = 1 + good_revs.nr;
struct commit **rev = xmalloc(len * sizeof(*rev));
int i, n = 0;
rev[n++] = get_commit_reference(current_bad_sha1);
for (i = 0; i < good_revs.nr; i++)
rev[n++] = get_commit_reference(good_revs.sha1[i]);
*rev_nr = n;
return rev;
}
static void handle_bad_merge_base(void)
{
if (is_expected_rev(current_bad_sha1)) {
char *bad_hex = sha1_to_hex(current_bad_sha1);
char *good_hex = join_sha1_array_hex(&good_revs, ' ');
fprintf(stderr, "The merge base %s is bad.\n"
"This means the bug has been fixed "
"between %s and [%s].\n",
bad_hex, bad_hex, good_hex);
exit(3);
}
fprintf(stderr, "Some good revs are not ancestor of the bad rev.\n"
"git bisect cannot work properly in this case.\n"
"Maybe you mistake good and bad revs?\n");
exit(1);
}
static void handle_skipped_merge_base(const unsigned char *mb)
{
char *mb_hex = sha1_to_hex(mb);
char *bad_hex = sha1_to_hex(current_bad_sha1);
char *good_hex = join_sha1_array_hex(&good_revs, ' ');
warning("the merge base between %s and [%s] "
"must be skipped.\n"
"So we cannot be sure the first bad commit is "
"between %s and %s.\n"
"We continue anyway.",
bad_hex, good_hex, mb_hex, bad_hex);
free(good_hex);
}
/*
* "check_merge_bases" checks that merge bases are not "bad".
*
* - If one is "bad", it means the user assumed something wrong
* and we must exit with a non 0 error code.
* - If one is "good", that's good, we have nothing to do.
* - If one is "skipped", we can't know but we should warn. * - If we don't know, we should check it out and ask the user to test.
*/
static void check_merge_bases(int no_checkout)
{
struct commit_list *result;
int rev_nr;
struct commit **rev = get_bad_and_good_commits(&rev_nr);
result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1, 0);
for (; result; result = result->next) {
const unsigned char *mb = result->item->object.sha1;
if (!hashcmp(mb, current_bad_sha1)) {
handle_bad_merge_base();
} else if (0 <= sha1_array_lookup(&good_revs, mb)) {
continue;
} else if (0 <= sha1_array_lookup(&skipped_revs, mb)) {
handle_skipped_merge_base(mb);
} else {
printf("Bisecting: a merge base must be tested\n");
exit(bisect_checkout(sha1_to_hex(mb), no_checkout));
}
}
free(rev);
free_commit_list(result);
}
static int check_ancestors(const char *prefix)
{
struct rev_info revs;
struct object_array pending_copy;
int res;
bisect_rev_setup(&revs, prefix, "^%s", "%s", 0);
/* Save pending objects, so they can be cleaned up later. */
pending_copy = revs.pending;
revs.leak_pending = 1;
/*
* bisect_common calls prepare_revision_walk right away, which
* (together with .leak_pending = 1) makes us the sole owner of
* the list of pending objects.
*/
bisect_common(&revs);
res = (revs.commits != NULL);
/* Clean up objects used, as they will be reused. */
clear_commit_marks_for_object_array(&pending_copy, ALL_REV_FLAGS);
free(pending_copy.objects);
return res;
}
/*
* "check_good_are_ancestors_of_bad" checks that all "good" revs are
* ancestor of the "bad" rev.
*
* If that's not the case, we need to check the merge bases.
* If a merge base must be tested by the user, its source code will be
* checked out to be tested by the user and we will exit.
*/
static void check_good_are_ancestors_of_bad(const char *prefix, int no_checkout)
{
const char *filename = git_path("BISECT_ANCESTORS_OK");
struct stat st;
int fd;
if (!current_bad_sha1) die("a bad revision is needed");
/* Check if file BISECT_ANCESTORS_OK exists. */
if (!stat(filename, &st) && S_ISREG(st.st_mode))
return;
/* Bisecting with no good rev is ok. */
if (good_revs.nr == 0)
return;
/* Check if all good revs are ancestor of the bad rev. */
if (check_ancestors(prefix))
check_merge_bases(no_checkout);
/* Create file BISECT_ANCESTORS_OK. */
fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
if (fd < 0)
warning("could not create file '%s': %s",
filename, strerror(errno));
else
close(fd);
}
/*
* This does "git diff-tree --pretty COMMIT" without one fork+exec.
*/
static void show_diff_tree(const char *prefix, struct commit *commit)
{
struct rev_info opt;
/* diff-tree init */
init_revisions(&opt, prefix);
git_config(git_diff_basic_config, NULL); /* no "diff" UI options */
opt.abbrev = 0;
opt.diff = 1;
/* This is what "--pretty" does */
opt.verbose_header = 1;
opt.use_terminator = 0;
opt.commit_format = CMIT_FMT_DEFAULT;
/* diff-tree init */
if (!opt.diffopt.output_format)
opt.diffopt.output_format = DIFF_FORMAT_RAW;
log_tree_commit(&opt, commit);
}
/*
* We use the convention that exiting with an exit code 10 means that
* the bisection process finished successfully.
* In this case the calling shell script should exit 0.
*
* If no_checkout is non-zero, the bisection process does not
* checkout the trial commit but instead simply updates BISECT_HEAD.
*/
int bisect_next_all(const char *prefix, int no_checkout)
{
struct rev_info revs;
struct commit_list *tried;
int reaches = 0, all = 0, nr, steps;
const unsigned char *bisect_rev;
char bisect_rev_hex[41];
if (read_bisect_refs())
die("reading bisect refs failed");
check_good_are_ancestors_of_bad(prefix, no_checkout);
bisect_rev_setup(&revs, prefix, "%s", "^%s", 1); revs.limited = 1;
bisect_common(&revs);
revs.commits = find_bisection(revs.commits, &reaches, &all,
!!skipped_revs.nr);
revs.commits = managed_skipped(revs.commits, &tried);
if (!revs.commits) {
/*
* We should exit here only if the "bad"
* commit is also a "skip" commit.
*/
exit_if_skipped_commits(tried, NULL);
printf("%s was both good and bad\n",
sha1_to_hex(current_bad_sha1));
exit(1);
}
if (!all) {
fprintf(stderr, "No testable commit found.\n"
"Maybe you started with bad path parameters?\n");
exit(4);
}
bisect_rev = revs.commits->item->object.sha1;
memcpy(bisect_rev_hex, sha1_to_hex(bisect_rev), 41);
if (!hashcmp(bisect_rev, current_bad_sha1)) {
exit_if_skipped_commits(tried, current_bad_sha1);
printf("%s is the first bad commit\n", bisect_rev_hex);
show_diff_tree(prefix, revs.commits->item);
/* This means the bisection process succeeded. */
exit(10);
}
nr = all - reaches - 1;
steps = estimate_bisect_steps(all);
printf("Bisecting: %d revision%s left to test after this "
"(roughly %d step%s)\n", nr, (nr == 1 ? "" : "s"),
steps, (steps == 1 ? "" : "s"));
return bisect_checkout(bisect_rev_hex, no_checkout);
}