git/pack-refs.c
Michael Haggerty c29c46fa2e pack-refs: add fully-peeled trait
Older versions of pack-refs did not write peel lines for
refs outside of refs/tags. This meant that on reading the
pack-refs file, we might set the REF_KNOWS_PEELED flag for
such a ref, even though we do not know anything about its
peeled value.

The previous commit updated the writer to always peel, no
matter what the ref is. That means that packed-refs files
written by newer versions of git are fine to be read by both
old and new versions of git. However, we still have the
problem of reading packed-refs files written by older
versions of git, or by other implementations which have not
yet learned the same trick.

The simplest fix would be to always unset the
REF_KNOWS_PEELED flag for refs outside of refs/tags that do
not have a peel line (if it has a peel line, we know it is
valid, but we cannot assume a missing peel line means
anything). But that loses an important optimization, as
upload-pack should not need to load the object pointed to by
refs/heads/foo to determine that it is not a tag.

Instead, we add a "fully-peeled" trait to the packed-refs
file. If it is set, we know that we can trust a missing peel
line to mean that a ref cannot be peeled. Otherwise, we fall
back to assuming nothing.

[commit message and tests by Jeff King <peff@peff.net>]

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-03-18 08:06:28 -07:00

149 lines
3.3 KiB
C

#include "cache.h"
#include "refs.h"
#include "tag.h"
#include "pack-refs.h"
struct ref_to_prune {
struct ref_to_prune *next;
unsigned char sha1[20];
char name[FLEX_ARRAY];
};
struct pack_refs_cb_data {
unsigned int flags;
struct ref_to_prune *ref_to_prune;
FILE *refs_file;
};
static int do_not_prune(int flags)
{
/* If it is already packed or if it is a symref,
* do not prune it.
*/
return (flags & (REF_ISSYMREF|REF_ISPACKED));
}
static int handle_one_ref(const char *path, const unsigned char *sha1,
int flags, void *cb_data)
{
struct pack_refs_cb_data *cb = cb_data;
struct object *o;
int is_tag_ref;
/* Do not pack the symbolic refs */
if ((flags & REF_ISSYMREF))
return 0;
is_tag_ref = !prefixcmp(path, "refs/tags/");
/* ALWAYS pack refs that were already packed or are tags */
if (!(cb->flags & PACK_REFS_ALL) && !is_tag_ref && !(flags & REF_ISPACKED))
return 0;
fprintf(cb->refs_file, "%s %s\n", sha1_to_hex(sha1), path);
o = parse_object_or_die(sha1, path);
if (o->type == OBJ_TAG) {
o = deref_tag(o, path, 0);
if (o)
fprintf(cb->refs_file, "^%s\n",
sha1_to_hex(o->sha1));
}
if ((cb->flags & PACK_REFS_PRUNE) && !do_not_prune(flags)) {
int namelen = strlen(path) + 1;
struct ref_to_prune *n = xcalloc(1, sizeof(*n) + namelen);
hashcpy(n->sha1, sha1);
strcpy(n->name, path);
n->next = cb->ref_to_prune;
cb->ref_to_prune = n;
}
return 0;
}
/*
* Remove empty parents, but spare refs/ and immediate subdirs.
* Note: munges *name.
*/
static void try_remove_empty_parents(char *name)
{
char *p, *q;
int i;
p = name;
for (i = 0; i < 2; i++) { /* refs/{heads,tags,...}/ */
while (*p && *p != '/')
p++;
/* tolerate duplicate slashes; see check_refname_format() */
while (*p == '/')
p++;
}
for (q = p; *q; q++)
;
while (1) {
while (q > p && *q != '/')
q--;
while (q > p && *(q-1) == '/')
q--;
if (q == p)
break;
*q = '\0';
if (rmdir(git_path("%s", name)))
break;
}
}
/* make sure nobody touched the ref, and unlink */
static void prune_ref(struct ref_to_prune *r)
{
struct ref_lock *lock = lock_ref_sha1(r->name + 5, r->sha1);
if (lock) {
unlink_or_warn(git_path("%s", r->name));
unlock_ref(lock);
try_remove_empty_parents(r->name);
}
}
static void prune_refs(struct ref_to_prune *r)
{
while (r) {
prune_ref(r);
r = r->next;
}
}
static struct lock_file packed;
int pack_refs(unsigned int flags)
{
int fd;
struct pack_refs_cb_data cbdata;
memset(&cbdata, 0, sizeof(cbdata));
cbdata.flags = flags;
fd = hold_lock_file_for_update(&packed, git_path("packed-refs"),
LOCK_DIE_ON_ERROR);
cbdata.refs_file = fdopen(fd, "w");
if (!cbdata.refs_file)
die_errno("unable to create ref-pack file structure");
/* perhaps other traits later as well */
fprintf(cbdata.refs_file, "# pack-refs with: peeled fully-peeled \n");
for_each_ref(handle_one_ref, &cbdata);
if (ferror(cbdata.refs_file))
die("failed to write ref-pack file");
if (fflush(cbdata.refs_file) || fsync(fd) || fclose(cbdata.refs_file))
die_errno("failed to write ref-pack file");
/*
* Since the lock file was fdopen()'ed and then fclose()'ed above,
* assign -1 to the lock file descriptor so that commit_lock_file()
* won't try to close() it.
*/
packed.fd = -1;
if (commit_lock_file(&packed) < 0)
die_errno("unable to overwrite old ref-pack file");
prune_refs(cbdata.ref_to_prune);
return 0;
}