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git/builtin/describe.c
Jeff King 36a317929b refs: switch peel_ref() to peel_iterated_oid() 
The peel_ref() interface is confusing and error-prone:

  - it's typically used by ref iteration callbacks that have both a
    refname and oid. But since they pass only the refname, we may load
    the ref value from the filesystem again. This is inefficient, but
    also means we are open to a race if somebody simultaneously updates
    the ref. E.g., this:

      int some_ref_cb(const char *refname, const struct object_id *oid, ...)
      {
              if (!peel_ref(refname, &peeled))
                      printf("%s peels to %s",
                             oid_to_hex(oid), oid_to_hex(&peeled);
      }

    could print nonsense. It is correct to say "refname peels to..."
    (you may see the "before" value or the "after" value, either of
    which is consistent), but mentioning both oids may be mixing
    before/after values.

    Worse, whether this is possible depends on whether the optimization
    to read from the current iterator value kicks in. So it is actually
    not possible with:

      for_each_ref(some_ref_cb);

    but it _is_ possible with:

      head_ref(some_ref_cb);

    which does not use the iterator mechanism (though in practice, HEAD
    should never peel to anything, so this may not be triggerable).

  - it must take a fully-qualified refname for the read_ref_full() code
    path to work. Yet we routinely pass it partial refnames from
    callbacks to for_each_tag_ref(), etc. This happens to work when
    iterating because there we do not call read_ref_full() at all, and
    only use the passed refname to check if it is the same as the
    iterator. But the requirements for the function parameters are quite
    unclear.

Instead of taking a refname, let's instead take an oid. That fixes both
problems. It's a little funny for a "ref" function not to involve refs
at all. The key thing is that it's optimizing under the hood based on
having access to the ref iterator. So let's change the name to make it
clear why you'd want this function versus just peel_object().

There are two other directions I considered but rejected:

  - we could pass the peel information into the each_ref_fn callback.
    However, we don't know if the caller actually wants it or not. For
    packed-refs, providing it is essentially free. But for loose refs,
    we actually have to peel the object, which would be wasteful in most
    cases. We could likewise pass in a flag to the callback indicating
    whether the peeled information is known, but that complicates those
    callbacks, as they then have to decide whether to manually peel
    themselves. Plus it requires changing the interface of every
    callback, whether they care about peeling or not, and there are many
    of them.

  - we could make a function to return the peeled value of the current
    iterated ref (computing it if necessary), and BUG() otherwise. I.e.:

      int peel_current_iterated_ref(struct object_id *out);

    Each of the current callers is an each_ref_fn callback, so they'd
    mostly be happy. But:

      - we use those callbacks with functions like head_ref(), which do
        not use the iteration code. So we'd need to handle the fallback
        case there, anyway.

      - it's possible that a caller would want to call into generic code
        that sometimes is used during iteration and sometimes not. This
        encapsulates the logic to do the fast thing when possible, and
        fallback when necessary.

The implementation is mostly obvious, but I want to call out a few
things in the patch:

  - the test-tool coverage for peel_ref() is now meaningless, as it all
    collapses to a single peel_object() call (arguably they were pretty
    uninteresting before; the tricky part of that function is the
    fast-path we see during iteration, but these calls didn't trigger
    that). I've just dropped it entirely, though note that some other
    tests relied on the tags we created; I've moved that creation to the
    tests where it matters.

  - we no longer need to take a ref_store parameter, since we'd never
    look up a ref now. We do still rely on a global "current iterator"
    variable which _could_ be kept per-ref-store. But in practice this
    is only useful if there are multiple recursive iterations, at which
    point the more appropriate solution is probably a stack of
    iterators. No caller used the actual ref-store parameter anyway
    (they all call the wrapper that passes the_repository).

  - the original only kicked in the optimization when the "refname"
    pointer matched (i.e., not string comparison). We do likewise with
    the "oid" parameter here, but fall back to doing an actual oideq()
    call. This in theory lets us kick in the optimization more often,
    though in practice no current caller cares. It should never be
    wrong, though (peeling is a property of an object, so two refs
    pointing to the same object would peel identically).

  - the original took care not to touch the peeled out-parameter unless
    we found something to put in it. But no caller cares about this, and
    anyway, it is enforced by peel_object() itself (and even in the
    optimized iterator case, that's where we eventually end up). We can
    shorten the code and avoid an extra copy by just passing the
    out-parameter through the stack.

Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-01-21 15:51:31 -08:00

682 lines
18 KiB
C
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#define USE_THE_INDEX_COMPATIBILITY_MACROS
#include "cache.h"
#include "config.h"
#include "lockfile.h"
#include "commit.h"
#include "tag.h"
#include "blob.h"
#include "refs.h"
#include "builtin.h"
#include "exec-cmd.h"
#include "parse-options.h"
#include "revision.h"
#include "diff.h"
#include "hashmap.h"
#include "strvec.h"
#include "run-command.h"
#include "object-store.h"
#include "list-objects.h"
#include "commit-slab.h"
#define MAX_TAGS (FLAG_BITS - 1)
define_commit_slab(commit_names, struct commit_name *);
static const char * const describe_usage[] = {
N_("git describe [<options>] [<commit-ish>...]"),
N_("git describe [<options>] --dirty"),
NULL
};
static int debug; /* Display lots of verbose info */
static int all; /* Any valid ref can be used */
static int tags; /* Allow lightweight tags */
static int longformat;
static int first_parent;
static int abbrev = -1; /* unspecified */
static int max_candidates = 10;
static struct hashmap names;
static int have_util;
static struct string_list patterns = STRING_LIST_INIT_NODUP;
static struct string_list exclude_patterns = STRING_LIST_INIT_NODUP;
static int always;
static const char *suffix, *dirty, *broken;
static struct commit_names commit_names;
/* diff-index command arguments to check if working tree is dirty. */
static const char *diff_index_args[] = {
"diff-index", "--quiet", "HEAD", "--", NULL
};
struct commit_name {
struct hashmap_entry entry;
struct object_id peeled;
struct tag *tag;
unsigned prio:2; /* annotated tag = 2, tag = 1, head = 0 */
unsigned name_checked:1;
unsigned misnamed:1;
struct object_id oid;
char *path;
};
static const char *prio_names[] = {
N_("head"), N_("lightweight"), N_("annotated"),
};
static int commit_name_neq(const void *unused_cmp_data,
const struct hashmap_entry *eptr,
const struct hashmap_entry *entry_or_key,
const void *peeled)
{
const struct commit_name *cn1, *cn2;
cn1 = container_of(eptr, const struct commit_name, entry);
cn2 = container_of(entry_or_key, const struct commit_name, entry);
return !oideq(&cn1->peeled, peeled ? peeled : &cn2->peeled);
}
static inline struct commit_name *find_commit_name(const struct object_id *peeled)
{
return hashmap_get_entry_from_hash(&names, oidhash(peeled), peeled,
struct commit_name, entry);
}
static int replace_name(struct commit_name *e,
int prio,
const struct object_id *oid,
struct tag **tag)
{
if (!e || e->prio < prio)
return 1;
if (e->prio == 2 && prio == 2) {
/* Multiple annotated tags point to the same commit.
* Select one to keep based upon their tagger date.
*/
struct tag *t;
if (!e->tag) {
t = lookup_tag(the_repository, &e->oid);
if (!t || parse_tag(t))
return 1;
e->tag = t;
}
t = lookup_tag(the_repository, oid);
if (!t || parse_tag(t))
return 0;
*tag = t;
if (e->tag->date < t->date)
return 1;
}
return 0;
}
static void add_to_known_names(const char *path,
const struct object_id *peeled,
int prio,
const struct object_id *oid)
{
struct commit_name *e = find_commit_name(peeled);
struct tag *tag = NULL;
if (replace_name(e, prio, oid, &tag)) {
if (!e) {
e = xmalloc(sizeof(struct commit_name));
oidcpy(&e->peeled, peeled);
hashmap_entry_init(&e->entry, oidhash(peeled));
hashmap_add(&names, &e->entry);
e->path = NULL;
}
e->tag = tag;
e->prio = prio;
e->name_checked = 0;
e->misnamed = 0;
oidcpy(&e->oid, oid);
free(e->path);
e->path = xstrdup(path);
}
}
static int get_name(const char *path, const struct object_id *oid, int flag, void *cb_data)
{
int is_tag = 0;
struct object_id peeled;
int is_annotated, prio;
const char *path_to_match = NULL;
if (skip_prefix(path, "refs/tags/", &path_to_match)) {
is_tag = 1;
} else if (all) {
if ((exclude_patterns.nr || patterns.nr) &&
!skip_prefix(path, "refs/heads/", &path_to_match) &&
!skip_prefix(path, "refs/remotes/", &path_to_match)) {
/* Only accept reference of known type if there are match/exclude patterns */
return 0;
}
} else {
/* Reject anything outside refs/tags/ unless --all */
return 0;
}
/*
* If we're given exclude patterns, first exclude any tag which match
* any of the exclude pattern.
*/
if (exclude_patterns.nr) {
struct string_list_item *item;
for_each_string_list_item(item, &exclude_patterns) {
if (!wildmatch(item->string, path_to_match, 0))
return 0;
}
}
/*
* If we're given patterns, accept only tags which match at least one
* pattern.
*/
if (patterns.nr) {
int found = 0;
struct string_list_item *item;
for_each_string_list_item(item, &patterns) {
if (!wildmatch(item->string, path_to_match, 0)) {
found = 1;
break;
}
}
if (!found)
return 0;
}
/* Is it annotated? */
if (!peel_iterated_oid(oid, &peeled)) {
is_annotated = !oideq(oid, &peeled);
} else {
oidcpy(&peeled, oid);
is_annotated = 0;
}
/*
* By default, we only use annotated tags, but with --tags
* we fall back to lightweight ones (even without --tags,
* we still remember lightweight ones, only to give hints
* in an error message). --all allows any refs to be used.
*/
if (is_annotated)
prio = 2;
else if (is_tag)
prio = 1;
else
prio = 0;
add_to_known_names(all ? path + 5 : path + 10, &peeled, prio, oid);
return 0;
}
struct possible_tag {
struct commit_name *name;
int depth;
int found_order;
unsigned flag_within;
};
static int compare_pt(const void *a_, const void *b_)
{
struct possible_tag *a = (struct possible_tag *)a_;
struct possible_tag *b = (struct possible_tag *)b_;
if (a->depth != b->depth)
return a->depth - b->depth;
if (a->found_order != b->found_order)
return a->found_order - b->found_order;
return 0;
}
static unsigned long finish_depth_computation(
struct commit_list **list,
struct possible_tag *best)
{
unsigned long seen_commits = 0;
while (*list) {
struct commit *c = pop_commit(list);
struct commit_list *parents = c->parents;
seen_commits++;
if (c->object.flags & best->flag_within) {
struct commit_list *a = *list;
while (a) {
struct commit *i = a->item;
if (!(i->object.flags & best->flag_within))
break;
a = a->next;
}
if (!a)
break;
} else
best->depth++;
while (parents) {
struct commit *p = parents->item;
parse_commit(p);
if (!(p->object.flags & SEEN))
commit_list_insert_by_date(p, list);
p->object.flags |= c->object.flags;
parents = parents->next;
}
}
return seen_commits;
}
static void append_name(struct commit_name *n, struct strbuf *dst)
{
if (n->prio == 2 && !n->tag) {
n->tag = lookup_tag(the_repository, &n->oid);
if (!n->tag || parse_tag(n->tag))
die(_("annotated tag %s not available"), n->path);
}
if (n->tag && !n->name_checked) {
if (strcmp(n->tag->tag, all ? n->path + 5 : n->path)) {
warning(_("tag '%s' is externally known as '%s'"),
n->path, n->tag->tag);
n->misnamed = 1;
}
n->name_checked = 1;
}
if (n->tag) {
if (all)
strbuf_addstr(dst, "tags/");
strbuf_addstr(dst, n->tag->tag);
} else {
strbuf_addstr(dst, n->path);
}
}
static void append_suffix(int depth, const struct object_id *oid, struct strbuf *dst)
{
strbuf_addf(dst, "-%d-g%s", depth, find_unique_abbrev(oid, abbrev));
}
static void describe_commit(struct object_id *oid, struct strbuf *dst)
{
struct commit *cmit, *gave_up_on = NULL;
struct commit_list *list;
struct commit_name *n;
struct possible_tag all_matches[MAX_TAGS];
unsigned int match_cnt = 0, annotated_cnt = 0, cur_match;
unsigned long seen_commits = 0;
unsigned int unannotated_cnt = 0;
cmit = lookup_commit_reference(the_repository, oid);
n = find_commit_name(&cmit->object.oid);
if (n && (tags || all || n->prio == 2)) {
/*
* Exact match to an existing ref.
*/
append_name(n, dst);
if (n->misnamed || longformat)
append_suffix(0, n->tag ? get_tagged_oid(n->tag) : oid, dst);
if (suffix)
strbuf_addstr(dst, suffix);
return;
}
if (!max_candidates)
die(_("no tag exactly matches '%s'"), oid_to_hex(&cmit->object.oid));
if (debug)
fprintf(stderr, _("No exact match on refs or tags, searching to describe\n"));
if (!have_util) {
struct hashmap_iter iter;
struct commit *c;
struct commit_name *n;
init_commit_names(&commit_names);
hashmap_for_each_entry(&names, &iter, n,
entry /* member name */) {
c = lookup_commit_reference_gently(the_repository,
&n->peeled, 1);
if (c)
*commit_names_at(&commit_names, c) = n;
}
have_util = 1;
}
list = NULL;
cmit->object.flags = SEEN;
commit_list_insert(cmit, &list);
while (list) {
struct commit *c = pop_commit(&list);
struct commit_list *parents = c->parents;
struct commit_name **slot;
seen_commits++;
slot = commit_names_peek(&commit_names, c);
n = slot ? *slot : NULL;
if (n) {
if (!tags && !all && n->prio < 2) {
unannotated_cnt++;
} else if (match_cnt < max_candidates) {
struct possible_tag *t = &all_matches[match_cnt++];
t->name = n;
t->depth = seen_commits - 1;
t->flag_within = 1u << match_cnt;
t->found_order = match_cnt;
c->object.flags |= t->flag_within;
if (n->prio == 2)
annotated_cnt++;
}
else {
gave_up_on = c;
break;
}
}
for (cur_match = 0; cur_match < match_cnt; cur_match++) {
struct possible_tag *t = &all_matches[cur_match];
if (!(c->object.flags & t->flag_within))
t->depth++;
}
/* Stop if last remaining path already covered by best candidate(s) */
if (annotated_cnt && !list) {
int best_depth = INT_MAX;
unsigned best_within = 0;
for (cur_match = 0; cur_match < match_cnt; cur_match++) {
struct possible_tag *t = &all_matches[cur_match];
if (t->depth < best_depth) {
best_depth = t->depth;
best_within = t->flag_within;
} else if (t->depth == best_depth) {
best_within |= t->flag_within;
}
}
if ((c->object.flags & best_within) == best_within) {
if (debug)
fprintf(stderr, _("finished search at %s\n"),
oid_to_hex(&c->object.oid));
break;
}
}
while (parents) {
struct commit *p = parents->item;
parse_commit(p);
if (!(p->object.flags & SEEN))
commit_list_insert_by_date(p, &list);
p->object.flags |= c->object.flags;
parents = parents->next;
if (first_parent)
break;
}
}
if (!match_cnt) {
struct object_id *cmit_oid = &cmit->object.oid;
if (always) {
strbuf_add_unique_abbrev(dst, cmit_oid, abbrev);
if (suffix)
strbuf_addstr(dst, suffix);
return;
}
if (unannotated_cnt)
die(_("No annotated tags can describe '%s'.\n"
"However, there were unannotated tags: try --tags."),
oid_to_hex(cmit_oid));
else
die(_("No tags can describe '%s'.\n"
"Try --always, or create some tags."),
oid_to_hex(cmit_oid));
}
QSORT(all_matches, match_cnt, compare_pt);
if (gave_up_on) {
commit_list_insert_by_date(gave_up_on, &list);
seen_commits--;
}
seen_commits += finish_depth_computation(&list, &all_matches[0]);
free_commit_list(list);
if (debug) {
static int label_width = -1;
if (label_width < 0) {
int i, w;
for (i = 0; i < ARRAY_SIZE(prio_names); i++) {
w = strlen(_(prio_names[i]));
if (label_width < w)
label_width = w;
}
}
for (cur_match = 0; cur_match < match_cnt; cur_match++) {
struct possible_tag *t = &all_matches[cur_match];
fprintf(stderr, " %-*s %8d %s\n",
label_width, _(prio_names[t->name->prio]),
t->depth, t->name->path);
}
fprintf(stderr, _("traversed %lu commits\n"), seen_commits);
if (gave_up_on) {
fprintf(stderr,
_("more than %i tags found; listed %i most recent\n"
"gave up search at %s\n"),
max_candidates, max_candidates,
oid_to_hex(&gave_up_on->object.oid));
}
}
append_name(all_matches[0].name, dst);
if (all_matches[0].name->misnamed || abbrev)
append_suffix(all_matches[0].depth, &cmit->object.oid, dst);
if (suffix)
strbuf_addstr(dst, suffix);
}
struct process_commit_data {
struct object_id current_commit;
struct object_id looking_for;
struct strbuf *dst;
struct rev_info *revs;
};
static void process_commit(struct commit *commit, void *data)
{
struct process_commit_data *pcd = data;
pcd->current_commit = commit->object.oid;
}
static void process_object(struct object *obj, const char *path, void *data)
{
struct process_commit_data *pcd = data;
if (oideq(&pcd->looking_for, &obj->oid) && !pcd->dst->len) {
reset_revision_walk();
describe_commit(&pcd->current_commit, pcd->dst);
strbuf_addf(pcd->dst, ":%s", path);
free_commit_list(pcd->revs->commits);
pcd->revs->commits = NULL;
}
}
static void describe_blob(struct object_id oid, struct strbuf *dst)
{
struct rev_info revs;
struct strvec args = STRVEC_INIT;
struct process_commit_data pcd = { null_oid, oid, dst, &revs};
strvec_pushl(&args, "internal: The first arg is not parsed",
"--objects", "--in-commit-order", "--reverse", "HEAD",
NULL);
repo_init_revisions(the_repository, &revs, NULL);
if (setup_revisions(args.nr, args.v, &revs, NULL) > 1)
BUG("setup_revisions could not handle all args?");
if (prepare_revision_walk(&revs))
die("revision walk setup failed");
traverse_commit_list(&revs, process_commit, process_object, &pcd);
reset_revision_walk();
}
static void describe(const char *arg, int last_one)
{
struct object_id oid;
struct commit *cmit;
struct strbuf sb = STRBUF_INIT;
if (debug)
fprintf(stderr, _("describe %s\n"), arg);
if (get_oid(arg, &oid))
die(_("Not a valid object name %s"), arg);
cmit = lookup_commit_reference_gently(the_repository, &oid, 1);
if (cmit)
describe_commit(&oid, &sb);
else if (oid_object_info(the_repository, &oid, NULL) == OBJ_BLOB)
describe_blob(oid, &sb);
else
die(_("%s is neither a commit nor blob"), arg);
puts(sb.buf);
if (!last_one)
clear_commit_marks(cmit, -1);
strbuf_release(&sb);
}
int cmd_describe(int argc, const char **argv, const char *prefix)
{
int contains = 0;
struct option options[] = {
OPT_BOOL(0, "contains", &contains, N_("find the tag that comes after the commit")),
OPT_BOOL(0, "debug", &debug, N_("debug search strategy on stderr")),
OPT_BOOL(0, "all", &all, N_("use any ref")),
OPT_BOOL(0, "tags", &tags, N_("use any tag, even unannotated")),
OPT_BOOL(0, "long", &longformat, N_("always use long format")),
OPT_BOOL(0, "first-parent", &first_parent, N_("only follow first parent")),
OPT__ABBREV(&abbrev),
OPT_SET_INT(0, "exact-match", &max_candidates,
N_("only output exact matches"), 0),
OPT_INTEGER(0, "candidates", &max_candidates,
N_("consider <n> most recent tags (default: 10)")),
OPT_STRING_LIST(0, "match", &patterns, N_("pattern"),
N_("only consider tags matching <pattern>")),
OPT_STRING_LIST(0, "exclude", &exclude_patterns, N_("pattern"),
N_("do not consider tags matching <pattern>")),
OPT_BOOL(0, "always", &always,
N_("show abbreviated commit object as fallback")),
{OPTION_STRING, 0, "dirty", &dirty, N_("mark"),
N_("append <mark> on dirty working tree (default: \"-dirty\")"),
PARSE_OPT_OPTARG, NULL, (intptr_t) "-dirty"},
{OPTION_STRING, 0, "broken", &broken, N_("mark"),
N_("append <mark> on broken working tree (default: \"-broken\")"),
PARSE_OPT_OPTARG, NULL, (intptr_t) "-broken"},
OPT_END(),
};
git_config(git_default_config, NULL);
argc = parse_options(argc, argv, prefix, options, describe_usage, 0);
if (abbrev < 0)
abbrev = DEFAULT_ABBREV;
if (max_candidates < 0)
max_candidates = 0;
else if (max_candidates > MAX_TAGS)
max_candidates = MAX_TAGS;
save_commit_buffer = 0;
if (longformat && abbrev == 0)
die(_("--long is incompatible with --abbrev=0"));
if (contains) {
struct string_list_item *item;
struct strvec args;
strvec_init(&args);
strvec_pushl(&args, "name-rev",
"--peel-tag", "--name-only", "--no-undefined",
NULL);
if (always)
strvec_push(&args, "--always");
if (!all) {
strvec_push(&args, "--tags");
for_each_string_list_item(item, &patterns)
strvec_pushf(&args, "--refs=refs/tags/%s", item->string);
for_each_string_list_item(item, &exclude_patterns)
strvec_pushf(&args, "--exclude=refs/tags/%s", item->string);
}
if (argc)
strvec_pushv(&args, argv);
else
strvec_push(&args, "HEAD");
return cmd_name_rev(args.nr, args.v, prefix);
}
hashmap_init(&names, commit_name_neq, NULL, 0);
for_each_rawref(get_name, NULL);
if (!hashmap_get_size(&names) && !always)
die(_("No names found, cannot describe anything."));
if (argc == 0) {
if (broken) {
struct child_process cp = CHILD_PROCESS_INIT;
strvec_pushv(&cp.args, diff_index_args);
cp.git_cmd = 1;
cp.no_stdin = 1;
cp.no_stdout = 1;
if (!dirty)
dirty = "-dirty";
switch (run_command(&cp)) {
case 0:
suffix = NULL;
break;
case 1:
suffix = dirty;
break;
default:
/* diff-index aborted abnormally */
suffix = broken;
}
} else if (dirty) {
struct lock_file index_lock = LOCK_INIT;
struct rev_info revs;
struct strvec args = STRVEC_INIT;
int fd, result;
setup_work_tree();
read_cache();
refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED,
NULL, NULL, NULL);
fd = hold_locked_index(&index_lock, 0);
if (0 <= fd)
repo_update_index_if_able(the_repository, &index_lock);
repo_init_revisions(the_repository, &revs, prefix);
strvec_pushv(&args, diff_index_args);
if (setup_revisions(args.nr, args.v, &revs, NULL) != 1)
BUG("malformed internal diff-index command line");
result = run_diff_index(&revs, 0);
if (!diff_result_code(&revs.diffopt, result))
suffix = NULL;
else
suffix = dirty;
}
describe("HEAD", 1);
} else if (dirty) {
die(_("--dirty is incompatible with commit-ishes"));
} else if (broken) {
die(_("--broken is incompatible with commit-ishes"));
} else {
while (argc-- > 0)
describe(*argv++, argc == 0);
}
return 0;
}
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