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Various issues around "reflog expire", e.g. using --updateref when
expiring a reflog for a symbolic reference, have been corrected
and/or made saner.

* mh/expire-updateref-fixes:
  reflog_expire(): never update a reference to null_sha1
  reflog_expire(): ignore --updateref for symbolic references
  reflog: improve and update documentation
  struct ref_lock: delete the force_write member
  lock_ref_sha1_basic(): do not set force_write for missing references
  write_ref_sha1(): move write elision test to callers
  write_ref_sha1(): remove check for lock == NULL
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Junio C Hamano committed Mar 10, 2015
2 parents 2d659f7 + 423c688 commit 82b7e65
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144 changes: 86 additions & 58 deletions Documentation/git-reflog.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -17,85 +17,113 @@ The command takes various subcommands, and different options
depending on the subcommand:

[verse]
'git reflog expire' [--dry-run] [--stale-fix] [--verbose]
[--expire=<time>] [--expire-unreachable=<time>] [--all] <refs>...
'git reflog delete' ref@\{specifier\}...
'git reflog' ['show'] [log-options] [<ref>]
'git reflog expire' [--expire=<time>] [--expire-unreachable=<time>]
[--rewrite] [--updateref] [--stale-fix]
[--dry-run] [--verbose] [--all | <refs>...]
'git reflog delete' [--rewrite] [--updateref]
[--dry-run] [--verbose] ref@\{specifier\}...

Reference logs, or "reflogs", record when the tips of branches and
other references were updated in the local repository. Reflogs are
useful in various Git commands, to specify the old value of a
reference. For example, `HEAD@{2}` means "where HEAD used to be two
moves ago", `master@{one.week.ago}` means "where master used to point
to one week ago in this local repository", and so on. See
linkgit:gitrevisions[7] for more details.

This command manages the information recorded in the reflogs.

The "show" subcommand (which is also the default, in the absence of
any subcommands) shows the log of the reference provided in the
command-line (or `HEAD`, by default). The reflog covers all recent
actions, and in addition the `HEAD` reflog records branch switching.
`git reflog show` is an alias for `git log -g --abbrev-commit
--pretty=oneline`; see linkgit:git-log[1] for more information.

The "expire" subcommand prunes older reflog entries. Entries older
than `expire` time, or entries older than `expire-unreachable` time
and not reachable from the current tip, are removed from the reflog.
This is typically not used directly by end users -- instead, see
linkgit:git-gc[1].

The "delete" subcommand deletes single entries from the reflog. Its
argument must be an _exact_ entry (e.g. "`git reflog delete
master@{2}`"). This subcommand is also typically not used directly by
end users.

Reflog is a mechanism to record when the tip of branches are
updated. This command is to manage the information recorded in it.

The subcommand "expire" is used to prune older reflog entries.
Entries older than `expire` time, or entries older than
`expire-unreachable` time and not reachable from the current
tip, are removed from the reflog. This is typically not used
directly by the end users -- instead, see linkgit:git-gc[1].

The subcommand "show" (which is also the default, in the absence of any
subcommands) will take all the normal log options, and show the log of
the reference provided in the command-line (or `HEAD`, by default).
The reflog will cover all recent actions (HEAD reflog records branch switching
as well). It is an alias for `git log -g --abbrev-commit --pretty=oneline`;
see linkgit:git-log[1].
OPTIONS
-------

The reflog is useful in various Git commands, to specify the old value
of a reference. For example, `HEAD@{2}` means "where HEAD used to be
two moves ago", `master@{one.week.ago}` means "where master used to
point to one week ago", and so on. See linkgit:gitrevisions[7] for
more details.
Options for `show`
~~~~~~~~~~~~~~~~~~

To delete single entries from the reflog, use the subcommand "delete"
and specify the _exact_ entry (e.g. "`git reflog delete master@{2}`").
`git reflog show` accepts any of the options accepted by `git log`.


OPTIONS
-------
Options for `expire`
~~~~~~~~~~~~~~~~~~~~

--stale-fix::
This revamps the logic -- the definition of "broken commit"
becomes: a commit that is not reachable from any of the refs and
there is a missing object among the commit, tree, or blob
objects reachable from it that is not reachable from any of the
refs.
+
This computation involves traversing all the reachable objects, i.e. it
has the same cost as 'git prune'. Fortunately, once this is run, we
should not have to ever worry about missing objects, because the current
prune and pack-objects know about reflogs and protect objects referred by
them.
--all::
Process the reflogs of all references.

--expire=<time>::
Entries older than this time are pruned. Without the
option it is taken from configuration `gc.reflogExpire`,
which in turn defaults to 90 days. --expire=all prunes
entries regardless of their age; --expire=never turns off
pruning of reachable entries (but see --expire-unreachable).
Prune entries older than the specified time. If this option is
not specified, the expiration time is taken from the
configuration setting `gc.reflogExpire`, which in turn
defaults to 90 days. `--expire=all` prunes entries regardless
of their age; `--expire=never` turns off pruning of reachable
entries (but see `--expire-unreachable`).

--expire-unreachable=<time>::
Entries older than this time and not reachable from
the current tip of the branch are pruned. Without the
option it is taken from configuration
`gc.reflogExpireUnreachable`, which in turn defaults to
30 days. --expire-unreachable=all prunes unreachable
entries regardless of their age; --expire-unreachable=never
Prune entries older than `<time>` that are not reachable from
the current tip of the branch. If this option is not
specified, the expiration time is taken from the configuration
setting `gc.reflogExpireUnreachable`, which in turn defaults
to 30 days. `--expire-unreachable=all` prunes unreachable
entries regardless of their age; `--expire-unreachable=never`
turns off early pruning of unreachable entries (but see
--expire).

--all::
Instead of listing <refs> explicitly, prune all refs.
`--expire`).

--updateref::
Update the ref with the sha1 of the top reflog entry (i.e.
<ref>@\{0\}) after expiring or deleting.
Update the reference to the value of the top reflog entry (i.e.
<ref>@\{0\}) if the previous top entry was pruned. (This
option is ignored for symbolic references.)

--rewrite::
While expiring or deleting, adjust each reflog entry to ensure
that the `old` sha1 field points to the `new` sha1 field of the
previous entry.
If a reflog entry's predecessor is pruned, adjust its "old"
SHA-1 to be equal to the "new" SHA-1 field of the entry that
now precedes it.

--stale-fix::
Prune any reflog entries that point to "broken commits". A
broken commit is a commit that is not reachable from any of
the reference tips and that refers, directly or indirectly, to
a missing commit, tree, or blob object.
+
This computation involves traversing all the reachable objects, i.e. it
has the same cost as 'git prune'. It is primarily intended to fix
corruption caused by garbage collecting using older versions of Git,
which didn't protect objects referred to by reflogs.

-n::
--dry-run::
Do not actually prune any entries; just show what would have
been pruned.

--verbose::
Print extra information on screen.


Options for `delete`
~~~~~~~~~~~~~~~~~~~~

`git reflog delete` accepts options `--updateref`, `--rewrite`, `-n`,
`--dry-run`, and `--verbose`, with the same meanings as when they are
used with `expire`.


GIT
---
Part of the linkgit:git[1] suite
9 changes: 3 additions & 6 deletions builtin/reflog.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,14 +8,11 @@
#include "revision.h"
#include "reachable.h"

/*
* reflog expire
*/

/* NEEDSWORK: switch to using parse_options */
static const char reflog_expire_usage[] =
"git reflog expire [--verbose] [--dry-run] [--stale-fix] [--expire=<time>] [--expire-unreachable=<time>] [--all] <refs>...";
"git reflog expire [--expire=<time>] [--expire-unreachable=<time>] [--rewrite] [--updateref] [--stale-fix] [--dry-run | -n] [--verbose] [--all] <refs>...";
static const char reflog_delete_usage[] =
"git reflog delete [--verbose] [--dry-run] [--rewrite] [--updateref] <refs>...";
"git reflog delete [--rewrite] [--updateref] [--dry-run | -n] [--verbose] <refs>...";

static unsigned long default_reflog_expire;
static unsigned long default_reflog_expire_unreachable;
Expand Down
65 changes: 37 additions & 28 deletions refs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,6 @@ struct ref_lock {
struct lock_file *lk;
unsigned char old_sha1[20];
int lock_fd;
int force_write;
};

/*
Expand Down Expand Up @@ -2277,7 +2276,6 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
int type, lflags;
int mustexist = (old_sha1 && !is_null_sha1(old_sha1));
int resolve_flags = 0;
int missing = 0;
int attempts_remaining = 3;

lock = xcalloc(1, sizeof(struct ref_lock));
Expand Down Expand Up @@ -2316,13 +2314,13 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
orig_refname, strerror(errno));
goto error_return;
}
missing = is_null_sha1(lock->old_sha1);
/* When the ref did not exist and we are creating it,
* make sure there is no existing ref that is packed
* whose name begins with our refname, nor a ref whose
* name is a proper prefix of our refname.
/*
* If the ref did not exist and we are creating it, make sure
* there is no existing packed ref whose name begins with our
* refname, nor a packed ref whose name is a proper prefix of
* our refname.
*/
if (missing &&
if (is_null_sha1(lock->old_sha1) &&
!is_refname_available(refname, skip, get_packed_refs(&ref_cache))) {
last_errno = ENOTDIR;
goto error_return;
Expand All @@ -2338,10 +2336,6 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
lock->ref_name = xstrdup(refname);
lock->orig_ref_name = xstrdup(orig_refname);
ref_file = git_path("%s", refname);
if (missing)
lock->force_write = 1;
if ((flags & REF_NODEREF) && (type & REF_ISSYMREF))
lock->force_write = 1;

retry:
switch (safe_create_leading_directories(ref_file)) {
Expand Down Expand Up @@ -2897,7 +2891,6 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
error("unable to lock %s for update", newrefname);
goto rollback;
}
lock->force_write = 1;
hashcpy(lock->old_sha1, orig_sha1);
if (write_ref_sha1(lock, orig_sha1, logmsg)) {
error("unable to write current sha1 into %s", newrefname);
Expand All @@ -2913,7 +2906,6 @@ int rename_ref(const char *oldrefname, const char *newrefname, const char *logms
goto rollbacklog;
}

lock->force_write = 1;
flag = log_all_ref_updates;
log_all_ref_updates = 0;
if (write_ref_sha1(lock, orig_sha1, NULL))
Expand Down Expand Up @@ -3099,14 +3091,6 @@ static int write_ref_sha1(struct ref_lock *lock,
static char term = '\n';
struct object *o;

if (!lock) {
errno = EINVAL;
return -1;
}
if (!lock->force_write && !hashcmp(lock->old_sha1, sha1)) {
unlock_ref(lock);
return 0;
}
o = parse_object(sha1);
if (!o) {
error("Trying to write ref %s with nonexistent object %s",
Expand Down Expand Up @@ -3851,15 +3835,28 @@ int ref_transaction_commit(struct ref_transaction *transaction,
int flags = update->flags;

if ((flags & REF_HAVE_NEW) && !is_null_sha1(update->new_sha1)) {
if (write_ref_sha1(update->lock, update->new_sha1,
update->msg)) {
int overwriting_symref = ((update->type & REF_ISSYMREF) &&
(update->flags & REF_NODEREF));

if (!overwriting_symref
&& !hashcmp(update->lock->old_sha1, update->new_sha1)) {
/*
* The reference already has the desired
* value, so we don't need to write it.
*/
unlock_ref(update->lock);
update->lock = NULL;
} else if (write_ref_sha1(update->lock, update->new_sha1,
update->msg)) {
update->lock = NULL; /* freed by write_ref_sha1 */
strbuf_addf(err, "Cannot update the ref '%s'.",
update->refname);
ret = TRANSACTION_GENERIC_ERROR;
goto cleanup;
} else {
/* freed by write_ref_sha1(): */
update->lock = NULL;
}
update->lock = NULL; /* freed by write_ref_sha1 */
}
}

Expand Down Expand Up @@ -4083,6 +4080,7 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
struct ref_lock *lock;
char *log_file;
int status = 0;
int type;

memset(&cb, 0, sizeof(cb));
cb.flags = flags;
Expand All @@ -4094,7 +4092,7 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
* reference itself, plus we might need to update the
* reference if --updateref was specified:
*/
lock = lock_ref_sha1_basic(refname, sha1, NULL, 0, NULL);
lock = lock_ref_sha1_basic(refname, sha1, NULL, 0, &type);
if (!lock)
return error("cannot lock ref '%s'", refname);
if (!reflog_exists(refname)) {
Expand Down Expand Up @@ -4131,10 +4129,21 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
(*cleanup_fn)(cb.policy_cb);

if (!(flags & EXPIRE_REFLOGS_DRY_RUN)) {
/*
* It doesn't make sense to adjust a reference pointed
* to by a symbolic ref based on expiring entries in
* the symbolic reference's reflog. Nor can we update
* a reference if there are no remaining reflog
* entries.
*/
int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
!(type & REF_ISSYMREF) &&
!is_null_sha1(cb.last_kept_sha1);

if (close_lock_file(&reflog_lock)) {
status |= error("couldn't write %s: %s", log_file,
strerror(errno));
} else if ((flags & EXPIRE_REFLOGS_UPDATE_REF) &&
} else if (update &&
(write_in_full(lock->lock_fd,
sha1_to_hex(cb.last_kept_sha1), 40) != 40 ||
write_str_in_full(lock->lock_fd, "\n") != 1 ||
Expand All @@ -4145,7 +4154,7 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
} else if (commit_lock_file(&reflog_lock)) {
status |= error("unable to commit reflog '%s' (%s)",
log_file, strerror(errno));
} else if ((flags & EXPIRE_REFLOGS_UPDATE_REF) && commit_ref(lock)) {
} else if (update && commit_ref(lock)) {
status |= error("couldn't set %s", lock->ref_name);
}
}
Expand Down

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