Re: [PATCH v3 00/14] ref-transactions-reflog

10 messages, 4 authors, 2016-06-15 · open the first message on its own page

Re: [PATCH v3 00/14] ref-transactions-reflog

From: Junio C Hamano <hidden>
Date: 2016-06-15 23:02:59

Michael Haggerty [off-list ref] writes:

quoted

Sorry, but I lost track---which one is inside and which one is
outside?

By "inside" I mean the code that would be within the reference-handling
library if we had such a thing; i.e., implemented in refs.c. By
"outside" I mean in the code that calls the library; in this case the
"outside" code would live in builtin/reflog.c.

In other words, I'd prefer the "outside" code in builtin/reflog.c to
look vaguely like

    expire_reflogs_for_me_please(refname,
                                 should_expire_cb, cbdata, flags)

rather than
... (written as a client of the ref API) ...

OK, I very much agree with that.

Re: [PATCH v3 00/14] ref-transactions-reflog

From: Stefan Beller <hidden>
Date: 2016-06-15 23:02:59

Sorry for the long delay.
Thanks for the explanation and discussion.

So do I understand it right, that you are not opposing
the introduction of "everything should go through transactions"
but rather the detail and abstraction level of the API?

So starting from Michaels proposal in the first response:

1. Add a reflog entry when a reference is updated in a transaction.

ok

2. Rename a reflog file when the corresponding reference is renamed.

This should happen within the same transaction as the reference is
renamed, right?
So we don't have a multistep process here, which may abort in between having the
reference updated and a broken reflog or vice versa. We want to either
have both
the ref and the reflog updated or neither.

3. Delete the reflog when the corresponding reference is deleted [1].

also as one transaction?

4. Configure a reference to be reflogged.
5. Configure a reference to not be reflogged anymore and delete any
   existing reflog.

Why do we need 4 and 5 here? Wouldn't all refs be reflog by default and
why do I want to exclude some?

6. Selectively expire old reflog entries, e.g., based on their age.

This is the maintenance operation, which you were talking about.
In my vision, this also should go into one transaction. So you have the
business logic figuring out all the changes ("drop reflog entry a b and d")
and within one transaction we can perform all of the changes.

Thanks,
Stefan


On Tue, Nov 18, 2014 at 1:28 PM, Junio C Hamano [off-list ref] wrote:

Michael Haggerty [off-list ref] writes:

quoted

Sorry, but I lost track---which one is inside and which one is
outside?

By "inside" I mean the code that would be within the reference-handling
library if we had such a thing; i.e., implemented in refs.c. By
"outside" I mean in the code that calls the library; in this case the
"outside" code would live in builtin/reflog.c.

In other words, I'd prefer the "outside" code in builtin/reflog.c to
look vaguely like

    expire_reflogs_for_me_please(refname,
                                 should_expire_cb, cbdata, flags)

rather than
... (written as a client of the ref API) ...

OK, I very much agree with that.

Re: [PATCH v3 00/14] ref-transactions-reflog

From: Jonathan Nieder <hidden>
Date: 2016-06-15 23:03:00

Hi,

Stefan Beller wrote:

Sorry for the long delay.
Thanks for the explanation and discussion.

So do I understand it right, that you are not opposing
the introduction of "everything should go through transactions"
but rather the detail and abstraction level of the API?

For what it's worth, I don't personally think it makes sense to put
the options supported by 'git reflog expire' into the transaction API
as top-level functions.

Instead, I think it makes sense, to start off, to support the same
building block operations that are used in the current file-based
code.  That may mean having an API that can't express tricks that e.g.
an SQL-based backend would be able to optimize (removing some items
from a reflog without copying the rest, filtering based on conditions
that can be expressed in SQL such as date, etc) but I think it's fine
as a starting point.  Later we can add new operations, change existing
ones, and so on, based on experience with real backends.

The write operations for file-based reflog handling are simple:

	- create a new reflog with a single reflog entry

	- add an entry to an existing reflog

	- (optional) copy a reflog wholesale --- this can be
	  implemented in terms of "add an entry", but copying in
	  blocks (or making a reflink, on filesystems that support
	  that) can make this faster

	- remove a reflog

The reflog bookkeeping involved in renaming a ref can be implemented
as copy + delete.

I also have some thoughts about how those operations can be
implemented without such a performance hit (reading the whole reflog
into memory as part of the transaction seems problematic to me), but
that should probably wait for a separate message (and I've talked
about it a bit in person).

[...]

4. Configure a reference to be reflogged.
5. Configure a reference to not be reflogged anymore and delete any
   existing reflog.

Why do we need 4 and 5 here? Wouldn't all refs be reflog by default and
why do I want to exclude some?

See --create-reflog in git-branch(1) and core.logallrefupdates in
git-config(1).

Reflogs are disabled by default in bare repositories, which makes it
easier for unnecessary objects on a server to be more promptly removed
by gcs after a non-fast-forward push.  I prefer to turn on reflogs
when setting up a git server for my personal use.  It might be worth
flipping that default (as an orthogonal change).

6. Selectively expire old reflog entries, e.g., based on their age.

This is the maintenance operation, which you were talking about.
In my vision, this also should go into one transaction. So you have the
business logic figuring out all the changes ("drop reflog entry a b and d")
and within one transaction we can perform all of the changes.

Makes sense.

Thanks,
Jonathan

Re: [PATCH v3 00/14] ref-transactions-reflog

From: Michael Haggerty <hidden>
Date: 2016-06-15 23:03:00

On 11/20/2014 12:22 AM, Stefan Beller wrote:

Sorry for the long delay.
Thanks for the explanation and discussion.

So do I understand it right, that you are not opposing
the introduction of "everything should go through transactions"
but rather the detail and abstraction level of the API?

Correct.

So starting from Michaels proposal in the first response:

1. Add a reflog entry when a reference is updated in a transaction.

ok

2. Rename a reflog file when the corresponding reference is renamed.

This should happen within the same transaction as the reference is
renamed, right?

Yes. Maybe there should be a "rename reference" operation that can be
added to a transaction, and it simply knows to rename any associated
reflogs. Then the calling code wouldn't have to worry about reflogs
explicitly in this case at all.

So we don't have a multistep process here, which may abort in between having the
reference updated and a broken reflog or vice versa. We want to either
have both
the ref and the reflog updated or neither.

Yes.

3. Delete the reflog when the corresponding reference is deleted [1].

also as one transaction?

It would be a side-effect of committing a transaction that contains a
reference deletion. The deletion of the reflog would be done at the same
time that the rest of the transaction is committed, and again the
calling code wouldn't have to explicitly worry about the reflogs.

4. Configure a reference to be reflogged.
5. Configure a reference to not be reflogged anymore and delete any
   existing reflog.

Why do we need 4 and 5 here? Wouldn't all refs be reflog by default and
why do I want to exclude some?

6. Selectively expire old reflog entries, e.g., based on their age.

This is the maintenance operation, which you were talking about.
In my vision, this also should go into one transaction. So you have the
business logic figuring out all the changes ("drop reflog entry a b and d")
and within one transaction we can perform all of the changes.

But if we take the approach described above, AFAICT this operation is
the only one that would require the caller to manipulate reflog entries
explicitly. And it has to iterate through the old reflog entries, decide
which ones to keep, possibly change its neighbors to eliminate gaps in
the chain, then stuff each of the reflog entries into a transaction one
by one. To allow this to be implemented on the caller side, the
transaction API has to be complicated in the following ways:

* Add a transaction_update_type (UPDATE_SHA1 vs. UPDATE_LOG).
* Add reflog_fd, reflog_lock, and committer members to struct ref_update.
* New function transaction_update_reflog().
* A new flag REFLOG_TRUNCATE that allows the reflog file to be truncated
before writing.
* Machinery that recognizes that a transaction contains multiple reflog
updates for the same reference and processes them specially to avoid
locking and rewriting the reflog file multiple times.

So this design has the caller serializing all reflog entries into
separate ref_update structs (which implies that they are held in RAM!)
only for ref_transaction_commit() to scan through all ref_updates
looking for reflog updates that go together so that they can be
processed as a whole. In other words, the caller picks the reflog apart
and then ref_transaction_commit() glues it back together. It's all very
contrived.

I suggest that the caller only be responsible for deciding which reflog
entries to keep (by supplying a callback function), and a new
expire_reflogs_for_me_please() API function be responsible for taking
out a lock, feeding the old reflog entries to the callback, expiring the
unwanted entries, optionally eliminating gaps in the chain (for the use
of "reflog [expire|delete] --rewrite"), writing the new reflog entries,
and optionally updating the reference itself (for the use of "reflog
[expire|delete] --updateref").

The benefit will be simpler code, a better separation of
responsibilities, and a simpler VTABLE that future reference backends
have to implement.

I would love to work on this but unfortunately have way too much on my
plate right now.

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu

Re: [PATCH v3 00/14] ref-transactions-reflog

From: Jonathan Nieder <hidden>
Date: 2016-06-15 23:03:00

Michael Haggerty wrote:

On 11/20/2014 12:22 AM, Stefan Beller wrote:

quoted

3. Delete the reflog when the corresponding reference is deleted [1].

also as one transaction?

It would be a side-effect of committing a transaction that contains a
reference deletion. The deletion of the reflog would be done at the same
time that the rest of the transaction is committed, and again the
calling code wouldn't have to explicitly worry about the reflogs.

There is "git reflog delete <ref>", for when you have logallrefupdates
disabled and had explicitly enabled reflogs for a particular ref and
now want to turn it off.

[...]

So this design has the caller serializing all reflog entries into
separate ref_update structs (which implies that they are held in RAM!)
only for ref_transaction_commit() to scan through all ref_updates
looking for reflog updates that go together so that they can be
processed as a whole. In other words, the caller picks the reflog apart
and then ref_transaction_commit() glues it back together. It's all very
contrived.

I think there is a simpler and more efficient way to implement this.

transaction_update_reflog() can append to a .lock file.
transaction_commit() then would rename it into place.

There is some fuss about naming the .lock file to avoid D/F conflicts,
which is a topic for a separate message.

I suggest that the caller only be responsible for deciding which reflog
entries to keep (by supplying a callback function),

That could be handy.  The basic operations described before would still
be needed, though:

	create a new reflog with one entry, for new refs

	append an entry to a reflog, for ref updates (and the associated
		symref reflog update)

	copy (or rename --- that's a more minor detail) a reflog, for
		renaming refs

	delete a reflog, for "git reflog delete"

And the "filter reflog" operation you are describing is implementable
using those four operations, with no performance hit when dealing with
reflogs stored in the files backend.

Providing these operations doesn't prevent adding "filter reflog using
callback" later if it turns out to be the right operation for other
backends.  It could turn out that some other primitive operations that
are easy as an SQL operation is more useful, like "delete reflog
entry" (without iterating over the others) or "expire entries older
than <date>".  The nice thing is that adding those wouldn't break any
code using the initial four operations described above.  So this seems
like a good starting point.

[...]

I would love to work on this but unfortunately have way too much on my
plate right now.

Of course code is always an easy way to change my mind, when the time
comes. ;-)

Thanks,
Jonathan

[PATCH 0/4] Using transactions for the reflog

From: Stefan Beller <hidden>
Date: 2016-06-15 23:03:07

This is the core part of the refs-transactions-reflog series[1],
which was in discussion for a bit already.

The idea is to have the reflog being part of the transactions, which
the refs are already using, so the we're moving towards a database
like API in the long run. This makes git easier to maintain as well 
as opening the possibility to replace the backend with a real database.

The first patch is essentially just some sed magic with reformatting
the code, so the naming convention fits better, because the transactions 
will handle both the refs as well as the reflog after this series. 

The second patch introduces a new enum field to indicate, if we deal with
a ref or with a reflog entry in the transaction. 

The meat and most of the lines of code are found in the 3rd patch.
We introduce a rather lengthy function transaction_update_reflog,
which prepares all the reflog related changes.
The transaction_commit function will then also put the reflog changes
in place in a "best effort" atomic way.
Unlike in previous versions, we don't keep all the reflog in memory,
but use a temporary file in $GIT_DIR instead and the update can be done
using an atomic rename(...).

One of my todos is to make the error handling in the transaction_update_reflog
function a bit less repetitive either during the discussion of this series
or as a follow up.

The last patch in this series makes use of the transaction system in the 
user facing code, when running "git reflog expire" for example. 

I'd appreciate any comments. 

Apart from sending feedback on the list, you can find this series 
at github[2] embedded into the longer version of the series.
In that series at github there are a few more patches[3], which are already
reviewed and residing in Junios repository or considered trivial cleanups.

Thanks,
Stefan

[1] http://comments.gmane.org/gmane.comp.version-control.git/259712
[2] https://github.com/stefanbeller/git/commits/todo_sb13_ref-transactions-reflog-as-file
[3] The first 2 commits on top of Git 2.2-rc3 are origin/sb/ref-transaction-unify-to-update, 
    the third is in origin/sb/log-ref-write-fd, then comes this series in 4 patches. 
    The remaining latest 4 patches are clean up patches, mainly removing parts from the refs API
    which are no longer in use. I do not include these in this patch series, as I don't want to
    scare people away with a huge bulk of messages.

Ronnie Sahlberg (4):
  refs.c: rename the transaction functions
  refs.c: add a new update_type field to ref_update
  refs.c: add a transaction function to append a reflog entry
  reflog.c: use a reflog transaction when writing during expire

 branch.c               |  13 +--
 builtin/commit.c       |  10 +-
 builtin/fetch.c        |  12 +--
 builtin/receive-pack.c |  13 ++-
 builtin/reflog.c       |  85 ++++++++---------
 builtin/replace.c      |  10 +-
 builtin/tag.c          |  10 +-
 builtin/update-ref.c   |  26 ++---
 fast-import.c          |  22 ++---
 refs.c                 | 251 ++++++++++++++++++++++++++++++++++++++++---------
 refs.h                 |  57 +++++++----
 sequencer.c            |  12 +--
 walker.c               |  10 +-
 13 files changed, 352 insertions(+), 179 deletions(-)

-- 
2.2.0.rc3

[PATCH 2/4] refs.c: add a new update_type field to ref_update

From: Stefan Beller <hidden>
Date: 2016-06-15 23:03:07

From: Ronnie Sahlberg <redacted>

Add a field that describes what type of update this refers to. For now
the only type is UPDATE_SHA1 but we will soon add more types.

Signed-off-by: Ronnie Sahlberg <redacted>
Signed-off-by: Stefan Beller <redacted>
---
 refs.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/refs.c b/refs.c
index f0f0d23..84e086f 100644
--- a/refs.c
+++ b/refs.c

@@ -3516,6 +3516,10 @@ int for_each_reflog(each_ref_fn fn, void *cb_data)
 	return retval;
 }
 
+enum transaction_update_type {
+	UPDATE_SHA1 = 0
+};
+
 /**
  * Information needed for a single ref update.  Set new_sha1 to the
  * new value or to zero to delete the ref.  To check the old value

@@ -3523,6 +3527,7 @@ int for_each_reflog(each_ref_fn fn, void *cb_data)
  * value or to zero to ensure the ref does not exist before update.
  */
 struct ref_update {
+	enum transaction_update_type update_type;
 	unsigned char new_sha1[20];
 	unsigned char old_sha1[20];
 	int flags; /* REF_NODEREF? */

@@ -3583,12 +3588,14 @@ void transaction_free(struct transaction *transaction)
 }
 
 static struct ref_update *add_update(struct transaction *transaction,
-				     const char *refname)
+				     const char *refname,
+				     enum transaction_update_type update_type)
 {
 	size_t len = strlen(refname);
 	struct ref_update *update = xcalloc(1, sizeof(*update) + len + 1);
 
 	strcpy((char *)update->refname, refname);
+	update->update_type = update_type;
 	ALLOC_GROW(transaction->updates, transaction->nr + 1, transaction->alloc);
 	transaction->updates[transaction->nr++] = update;
 	return update;

@@ -3618,7 +3625,7 @@ int transaction_update_ref(struct transaction *transaction,
 		return -1;
 	}
 
-	update = add_update(transaction, refname);
+	update = add_update(transaction, refname, UPDATE_SHA1);
 	hashcpy(update->new_sha1, new_sha1);
 	update->flags = flags;
 	update->have_old = have_old;

@@ -3696,13 +3703,17 @@ static int ref_update_reject_duplicates(struct ref_update **updates, int n,
 
 	assert(err);
 
-	for (i = 1; i < n; i++)
+	for (i = 1; i < n; i++) {
+		if (updates[i - 1]->update_type != UPDATE_SHA1 ||
+		    updates[i]->update_type != UPDATE_SHA1)
+			continue;
 		if (!strcmp(updates[i - 1]->refname, updates[i]->refname)) {
 			strbuf_addf(err,
 				    "Multiple updates for ref '%s' not allowed.",
 				    updates[i]->refname);
 			return 1;
 		}
+	}
 	return 0;
 }

@@ -3734,13 +3745,17 @@ int transaction_commit(struct transaction *transaction,
 		goto cleanup;
 	}
 
-	/* Acquire all locks while verifying old values */
+	/* Acquire all ref locks while verifying old values */
 	for (i = 0; i < n; i++) {
 		struct ref_update *update = updates[i];
 		int flags = update->flags;
 
+		if (update->update_type != UPDATE_SHA1)
+			continue;
+
 		if (is_null_sha1(update->new_sha1))
 			flags |= REF_DELETING;
+
 		update->lock = lock_ref_sha1_basic(update->refname,
 						   (update->have_old ?
 						    update->old_sha1 :

@@ -3762,6 +3777,8 @@ int transaction_commit(struct transaction *transaction,
 	for (i = 0; i < n; i++) {
 		struct ref_update *update = updates[i];
 
+		if (update->update_type != UPDATE_SHA1)
+			continue;
 		if (!is_null_sha1(update->new_sha1)) {
 			if (write_ref_sha1(update->lock, update->new_sha1,
 					   update->msg)) {

@@ -3779,6 +3796,8 @@ int transaction_commit(struct transaction *transaction,
 	for (i = 0; i < n; i++) {
 		struct ref_update *update = updates[i];
 
+		if (update->update_type != UPDATE_SHA1)
+			continue;
 		if (update->lock) {
 			if (delete_ref_loose(update->lock, update->type, err)) {
 				ret = TRANSACTION_GENERIC_ERROR;

-- 
2.2.0.rc3

[PATCH 4/4] reflog.c: use a reflog transaction when writing during expire

From: Stefan Beller <hidden>
Date: 2016-06-15 23:03:07

From: Ronnie Sahlberg <redacted>

Use a transaction for all updates during expire_reflog.

Signed-off-by: Ronnie Sahlberg <redacted>
Signed-off-by: Stefan Beller <redacted>
---
 builtin/reflog.c | 85 ++++++++++++++++++++++++--------------------------------
 1 file changed, 37 insertions(+), 48 deletions(-)

diff --git a/builtin/reflog.c b/builtin/reflog.c
index 2d85d26..6bb7454 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c

@@ -32,8 +32,11 @@ struct cmd_reflog_expire_cb {
 	int recno;
 };
 
+static struct strbuf err = STRBUF_INIT;
+
 struct expire_reflog_cb {
-	FILE *newlog;
+	struct transaction *t;
+	const char *refname;
 	enum {
 		UE_NORMAL,
 		UE_ALWAYS,

@@ -316,20 +319,18 @@ static int expire_reflog_ent(unsigned char *osha1, unsigned char *nsha1,
 	if (cb->cmd->recno && --(cb->cmd->recno) == 0)
 		goto prune;
 
-	if (cb->newlog) {
-		char sign = (tz < 0) ? '-' : '+';
-		int zone = (tz < 0) ? (-tz) : tz;
-		fprintf(cb->newlog, "%s %s %s %lu %c%04d\t%s",
-			sha1_to_hex(osha1), sha1_to_hex(nsha1),
-			email, timestamp, sign, zone,
-			message);
+	if (cb->t) {
+		if (transaction_update_reflog(cb->t, cb->refname, nsha1, osha1,
+					      email, timestamp, tz, message, 0,
+					      &err))
+			return -1;
 		hashcpy(cb->last_kept_sha1, nsha1);
 	}
 	if (cb->cmd->verbose)
 		printf("keep %s", message);
 	return 0;
  prune:
-	if (!cb->newlog)
+	if (!cb->t)
 		printf("would prune %s", message);
 	else if (cb->cmd->verbose)
 		printf("prune %s", message);

@@ -353,29 +354,26 @@ static int expire_reflog(const char *ref, const unsigned char *sha1, int unused,
 {
 	struct cmd_reflog_expire_cb *cmd = cb_data;
 	struct expire_reflog_cb cb;
-	struct ref_lock *lock;
-	char *log_file, *newlog_path = NULL;
 	struct commit *tip_commit;
 	struct commit_list *tips;
 	int status = 0;
 
 	memset(&cb, 0, sizeof(cb));
+	cb.refname = ref;
 
-	/*
-	 * we take the lock for the ref itself to prevent it from
-	 * getting updated.
-	 */
-	lock = lock_any_ref_for_update(ref, sha1, 0, NULL);
-	if (!lock)
-		return error("cannot lock ref '%s'", ref);
-	log_file = git_pathdup("logs/%s", ref);
 	if (!reflog_exists(ref))
 		goto finish;
-	if (!cmd->dry_run) {
-		newlog_path = git_pathdup("logs/%s.lock", ref);
-		cb.newlog = fopen(newlog_path, "w");
+	cb.t = transaction_begin(&err);
+	if (!cb.t) {
+		status |= error("%s", err.buf);
+		goto cleanup;
+	}
+	if (transaction_update_reflog(cb.t, cb.refname, null_sha1, null_sha1,
+				      NULL, 0, 0, NULL, REFLOG_TRUNCATE,
+				      &err)) {
+		status |= error("%s", err.buf);
+		goto cleanup;
 	}
-
 	cb.cmd = cmd;
 
 	if (!cmd->expire_unreachable || !strcmp(ref, "HEAD")) {

@@ -407,7 +405,10 @@ static int expire_reflog(const char *ref, const unsigned char *sha1, int unused,
 		mark_reachable(&cb);
 	}
 
-	for_each_reflog_ent(ref, expire_reflog_ent, &cb);
+	if (for_each_reflog_ent(ref, expire_reflog_ent, &cb)) {
+		status |= error("%s", err.buf);
+		goto cleanup;
+	}
 
 	if (cb.unreachable_expire_kind != UE_ALWAYS) {
 		if (cb.unreachable_expire_kind == UE_HEAD) {

@@ -420,32 +421,20 @@ static int expire_reflog(const char *ref, const unsigned char *sha1, int unused,
 		}
 	}
  finish:
-	if (cb.newlog) {
-		if (fclose(cb.newlog)) {
-			status |= error("%s: %s", strerror(errno),
-					newlog_path);
-			unlink(newlog_path);
-		} else if (cmd->updateref &&
-			(write_in_full(lock->lock_fd,
-				sha1_to_hex(cb.last_kept_sha1), 40) != 40 ||
-			 write_str_in_full(lock->lock_fd, "\n") != 1 ||
-			 close_ref(lock) < 0)) {
-			status |= error("Couldn't write %s",
-					lock->lk->filename.buf);
-			unlink(newlog_path);
-		} else if (rename(newlog_path, log_file)) {
-			status |= error("cannot rename %s to %s",
-					newlog_path, log_file);
-			unlink(newlog_path);
-		} else if (cmd->updateref && commit_ref(lock)) {
-			status |= error("Couldn't set %s", lock->ref_name);
-		} else {
-			adjust_shared_perm(log_file);
+	if (!cmd->dry_run) {
+		if (cmd->updateref &&
+		    transaction_update_ref(cb.t, cb.refname,
+					   cb.last_kept_sha1, sha1,
+					   0, 1, NULL, &err)) {
+			status |= error("%s", err.buf);
+			goto cleanup;
 		}
+		if (transaction_commit(cb.t, &err))
+			status |= error("%s", err.buf);
 	}
-	free(newlog_path);
-	free(log_file);
-	unlock_ref(lock);
+ cleanup:
+	transaction_free(cb.t);
+	strbuf_release(&err);
 	return status;
 }

-- 
2.2.0.rc3

[PATCH 1/4] refs.c: rename the transaction functions

From: Stefan Beller <hidden>
Date: 2016-06-15 23:03:07

From: Ronnie Sahlberg <redacted>

Rename the transaction functions. Remove the leading ref_ from the
names and append _ref to the names for functions that create/delete/
update sha1 refs.

Signed-off-by: Ronnie Sahlberg <redacted>
Signed-off-by: Stefan Beller <redacted>
---

This commit can be reproduced via
find . -name "*.[ch]" -print | xargs sed -i ' \
	s/REF_TRANSACTION_OPEN/TRANSACTION_OPEN/; \
	s/REF_TRANSACTION_CLOSED/TRANSACTION_CLOSED/; \
	s/ref_transaction_begin/transaction_begin/; \
	s/ref_transaction_commit/transaction_commit/; \
	s/ref_transaction_create/transaction_create_ref/; \
	s/ref_transaction_delete/transaction_delete_ref/; \
	s/ref_transaction_free/transaction_free/; \
	s/ref_transaction_update/transaction_update_ref/; \
	s/ref_transaction/transaction/'
modulo white space changes for alignment.

---
 branch.c               | 13 +++++----
 builtin/commit.c       | 10 +++----
 builtin/fetch.c        | 12 ++++----
 builtin/receive-pack.c | 13 ++++-----
 builtin/replace.c      | 10 +++----
 builtin/tag.c          | 10 +++----
 builtin/update-ref.c   | 26 ++++++++---------
 fast-import.c          | 22 +++++++-------
 refs.c                 | 78 +++++++++++++++++++++++++-------------------------
 refs.h                 | 36 +++++++++++------------
 sequencer.c            | 12 ++++----
 walker.c               | 10 +++----
 12 files changed, 126 insertions(+), 126 deletions(-)

diff --git a/branch.c b/branch.c
index 4bab55a..c8462de 100644
--- a/branch.c
+++ b/branch.c

@@ -279,16 +279,17 @@ void create_branch(const char *head,
 		log_all_ref_updates = 1;
 
 	if (!dont_change_ref) {
-		struct ref_transaction *transaction;
+		struct transaction *transaction;
 		struct strbuf err = STRBUF_INIT;
 
-		transaction = ref_transaction_begin(&err);
+		transaction = transaction_begin(&err);
 		if (!transaction ||
-		    ref_transaction_update(transaction, ref.buf, sha1,
-					   null_sha1, 0, !forcing, msg, &err) ||
-		    ref_transaction_commit(transaction, &err))
+		    transaction_update_ref(transaction, ref.buf, sha1,
+					   null_sha1, 0, !forcing, msg,
+					   &err) ||
+		    transaction_commit(transaction, &err))
 			die("%s", err.buf);
-		ref_transaction_free(transaction);
+		transaction_free(transaction);
 		strbuf_release(&err);
 	}

diff --git a/builtin/commit.c b/builtin/commit.c
index e108c53..f50b7df 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c

@@ -1673,7 +1673,7 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	struct stat statbuf;
 	struct commit *current_head = NULL;
 	struct commit_extra_header *extra = NULL;
-	struct ref_transaction *transaction;
+	struct transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 
 	if (argc == 2 && !strcmp(argv[1], "-h"))

@@ -1804,17 +1804,17 @@ int cmd_commit(int argc, const char **argv, const char *prefix)
 	strbuf_insert(&sb, 0, reflog_msg, strlen(reflog_msg));
 	strbuf_insert(&sb, strlen(reflog_msg), ": ", 2);
 
-	transaction = ref_transaction_begin(&err);
+	transaction = transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_update(transaction, "HEAD", sha1,
+	    transaction_update_ref(transaction, "HEAD", sha1,
 				   current_head
 				   ? current_head->object.sha1 : NULL,
 				   0, !!current_head, sb.buf, &err) ||
-	    ref_transaction_commit(transaction, &err)) {
+	    transaction_commit(transaction, &err)) {
 		rollback_index_files();
 		die("%s", err.buf);
 	}
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 
 	unlink(git_path("CHERRY_PICK_HEAD"));
 	unlink(git_path("REVERT_HEAD"));

diff --git a/builtin/fetch.c b/builtin/fetch.c
index 7b84d35..0be0b09 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c

@@ -404,7 +404,7 @@ static int s_update_ref(const char *action,
 {
 	char msg[1024];
 	char *rla = getenv("GIT_REFLOG_ACTION");
-	struct ref_transaction *transaction;
+	struct transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 	int ret, df_conflict = 0;

@@ -414,23 +414,23 @@ static int s_update_ref(const char *action,
 		rla = default_rla.buf;
 	snprintf(msg, sizeof(msg), "%s: %s", rla, action);
 
-	transaction = ref_transaction_begin(&err);
+	transaction = transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_update(transaction, ref->name, ref->new_sha1,
+	    transaction_update_ref(transaction, ref->name, ref->new_sha1,
 				   ref->old_sha1, 0, check_old, msg, &err))
 		goto fail;
 
-	ret = ref_transaction_commit(transaction, &err);
+	ret = transaction_commit(transaction, &err);
 	if (ret) {
 		df_conflict = (ret == TRANSACTION_NAME_CONFLICT);
 		goto fail;
 	}
 
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	strbuf_release(&err);
 	return 0;
 fail:
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	error("%s", err.buf);
 	strbuf_release(&err);
 	return df_conflict ? STORE_REF_ERROR_DF_CONFLICT

diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 32fc540..397abc9 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c

@@ -838,26 +838,25 @@ static const char *update(struct command *cmd, struct shallow_info *si)
 	}
 	else {
 		struct strbuf err = STRBUF_INIT;
-		struct ref_transaction *transaction;
+		struct transaction *transaction;
 
 		if (shallow_update && si->shallow_ref[cmd->index] &&
 		    update_shallow_ref(cmd, si))
 			return "shallow error";
 
-		transaction = ref_transaction_begin(&err);
+		transaction = transaction_begin(&err);
 		if (!transaction ||
-		    ref_transaction_update(transaction, namespaced_name,
+		    transaction_update_ref(transaction, namespaced_name,
 					   new_sha1, old_sha1, 0, 1, "push",
 					   &err) ||
-		    ref_transaction_commit(transaction, &err)) {
-			ref_transaction_free(transaction);
-
+		    transaction_commit(transaction, &err)) {
+			transaction_free(transaction);
 			rp_error("%s", err.buf);
 			strbuf_release(&err);
 			return "failed to update ref";
 		}
 
-		ref_transaction_free(transaction);
+		transaction_free(transaction);
 		strbuf_release(&err);
 		return NULL; /* good */
 	}

diff --git a/builtin/replace.c b/builtin/replace.c
index 85d39b5..5a7ab1f 100644
--- a/builtin/replace.c
+++ b/builtin/replace.c

@@ -155,7 +155,7 @@ static int replace_object_sha1(const char *object_ref,
 	unsigned char prev[20];
 	enum object_type obj_type, repl_type;
 	char ref[PATH_MAX];
-	struct ref_transaction *transaction;
+	struct transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 
 	obj_type = sha1_object_info(object, NULL);

@@ -169,14 +169,14 @@ static int replace_object_sha1(const char *object_ref,
 
 	check_ref_valid(object, prev, ref, sizeof(ref), force);
 
-	transaction = ref_transaction_begin(&err);
+	transaction = transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_update(transaction, ref, repl, prev,
+	    transaction_update_ref(transaction, ref, repl, prev,
 				   0, 1, NULL, &err) ||
-	    ref_transaction_commit(transaction, &err))
+	    transaction_commit(transaction, &err))
 		die("%s", err.buf);
 
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	return 0;
 }

diff --git a/builtin/tag.c b/builtin/tag.c
index e633f4e..5f3554b 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c

@@ -583,7 +583,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	const char *msgfile = NULL, *keyid = NULL;
 	struct msg_arg msg = { 0, STRBUF_INIT };
 	struct commit_list *with_commit = NULL;
-	struct ref_transaction *transaction;
+	struct transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 	struct option options[] = {
 		OPT_CMDMODE('l', "list", &cmdmode, N_("list tag names"), 'l'),

@@ -730,13 +730,13 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	if (annotate)
 		create_tag(object, tag, &buf, &opt, prev, object);
 
-	transaction = ref_transaction_begin(&err);
+	transaction = transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_update(transaction, ref.buf, object, prev,
+	    transaction_update_ref(transaction, ref.buf, object, prev,
 				   0, 1, NULL, &err) ||
-	    ref_transaction_commit(transaction, &err))
+	    transaction_commit(transaction, &err))
 		die("%s", err.buf);
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	if (force && !is_null_sha1(prev) && hashcmp(prev, object))
 		printf(_("Updated tag '%s' (was %s)\n"), tag, find_unique_abbrev(prev, DEFAULT_ABBREV));

diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 6c9be05..af08dd9 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c

@@ -175,7 +175,7 @@ static int parse_next_sha1(struct strbuf *input, const char **next,
  * depending on how line_termination is set.
  */
 
-static const char *parse_cmd_update(struct ref_transaction *transaction,
+static const char *parse_cmd_update(struct transaction *transaction,
 				    struct strbuf *input, const char *next)
 {
 	struct strbuf err = STRBUF_INIT;

@@ -198,7 +198,7 @@ static const char *parse_cmd_update(struct ref_transaction *transaction,
 	if (*next != line_termination)
 		die("update %s: extra input: %s", refname, next);
 
-	if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
+	if (transaction_update_ref(transaction, refname, new_sha1, old_sha1,
 				   update_flags, have_old, msg, &err))
 		die("%s", err.buf);

@@ -209,7 +209,7 @@ static const char *parse_cmd_update(struct ref_transaction *transaction,
 	return next;
 }
 
-static const char *parse_cmd_create(struct ref_transaction *transaction,
+static const char *parse_cmd_create(struct transaction *transaction,
 				    struct strbuf *input, const char *next)
 {
 	struct strbuf err = STRBUF_INIT;

@@ -229,7 +229,7 @@ static const char *parse_cmd_create(struct ref_transaction *transaction,
 	if (*next != line_termination)
 		die("create %s: extra input: %s", refname, next);
 
-	if (ref_transaction_create(transaction, refname, new_sha1,
+	if (transaction_create_ref(transaction, refname, new_sha1,
 				   update_flags, msg, &err))
 		die("%s", err.buf);

@@ -240,7 +240,7 @@ static const char *parse_cmd_create(struct ref_transaction *transaction,
 	return next;
 }
 
-static const char *parse_cmd_delete(struct ref_transaction *transaction,
+static const char *parse_cmd_delete(struct transaction *transaction,
 				    struct strbuf *input, const char *next)
 {
 	struct strbuf err = STRBUF_INIT;

@@ -264,7 +264,7 @@ static const char *parse_cmd_delete(struct ref_transaction *transaction,
 	if (*next != line_termination)
 		die("delete %s: extra input: %s", refname, next);
 
-	if (ref_transaction_delete(transaction, refname, old_sha1,
+	if (transaction_delete_ref(transaction, refname, old_sha1,
 				   update_flags, have_old, msg, &err))
 		die("%s", err.buf);

@@ -275,7 +275,7 @@ static const char *parse_cmd_delete(struct ref_transaction *transaction,
 	return next;
 }
 
-static const char *parse_cmd_verify(struct ref_transaction *transaction,
+static const char *parse_cmd_verify(struct transaction *transaction,
 				    struct strbuf *input, const char *next)
 {
 	struct strbuf err = STRBUF_INIT;

@@ -300,7 +300,7 @@ static const char *parse_cmd_verify(struct ref_transaction *transaction,
 	if (*next != line_termination)
 		die("verify %s: extra input: %s", refname, next);
 
-	if (ref_transaction_update(transaction, refname, new_sha1, old_sha1,
+	if (transaction_update_ref(transaction, refname, new_sha1, old_sha1,
 				   update_flags, have_old, msg, &err))
 		die("%s", err.buf);

@@ -320,7 +320,7 @@ static const char *parse_cmd_option(struct strbuf *input, const char *next)
 	return next + 8;
 }
 
-static void update_refs_stdin(struct ref_transaction *transaction)
+static void update_refs_stdin(struct transaction *transaction)
 {
 	struct strbuf input = STRBUF_INIT;
 	const char *next;

@@ -376,9 +376,9 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 
 	if (read_stdin) {
 		struct strbuf err = STRBUF_INIT;
-		struct ref_transaction *transaction;
+		struct transaction *transaction;
 
-		transaction = ref_transaction_begin(&err);
+		transaction = transaction_begin(&err);
 		if (!transaction)
 			die("%s", err.buf);
 		if (delete || no_deref || argc > 0)

@@ -386,9 +386,9 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 		if (end_null)
 			line_termination = '\0';
 		update_refs_stdin(transaction);
-		if (ref_transaction_commit(transaction, &err))
+		if (transaction_commit(transaction, &err))
 			die("%s", err.buf);
-		ref_transaction_free(transaction);
+		transaction_free(transaction);
 		strbuf_release(&err);
 		return 0;
 	}

diff --git a/fast-import.c b/fast-import.c
index d0bd285..152d944 100644
--- a/fast-import.c
+++ b/fast-import.c

@@ -1687,7 +1687,7 @@ found_entry:
 static int update_branch(struct branch *b)
 {
 	static const char *msg = "fast-import";
-	struct ref_transaction *transaction;
+	struct transaction *transaction;
 	unsigned char old_sha1[20];
 	struct strbuf err = STRBUF_INIT;

@@ -1713,17 +1713,17 @@ static int update_branch(struct branch *b)
 			return -1;
 		}
 	}
-	transaction = ref_transaction_begin(&err);
+	transaction = transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_update(transaction, b->name, b->sha1, old_sha1,
+	    transaction_update_ref(transaction, b->name, b->sha1, old_sha1,
 				   0, 1, msg, &err) ||
-	    ref_transaction_commit(transaction, &err)) {
-		ref_transaction_free(transaction);
+	    transaction_commit(transaction, &err)) {
+		transaction_free(transaction);
 		error("%s", err.buf);
 		strbuf_release(&err);
 		return -1;
 	}
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	strbuf_release(&err);
 	return 0;
 }

@@ -1745,9 +1745,9 @@ static void dump_tags(void)
 	struct tag *t;
 	struct strbuf ref_name = STRBUF_INIT;
 	struct strbuf err = STRBUF_INIT;
-	struct ref_transaction *transaction;
+	struct transaction *transaction;
 
-	transaction = ref_transaction_begin(&err);
+	transaction = transaction_begin(&err);
 	if (!transaction) {
 		failure |= error("%s", err.buf);
 		goto cleanup;

@@ -1756,17 +1756,17 @@ static void dump_tags(void)
 		strbuf_reset(&ref_name);
 		strbuf_addf(&ref_name, "refs/tags/%s", t->name);
 
-		if (ref_transaction_update(transaction, ref_name.buf, t->sha1,
+		if (transaction_update_ref(transaction, ref_name.buf, t->sha1,
 					   NULL, 0, 0, msg, &err)) {
 			failure |= error("%s", err.buf);
 			goto cleanup;
 		}
 	}
-	if (ref_transaction_commit(transaction, &err))
+	if (transaction_commit(transaction, &err))
 		failure |= error("%s", err.buf);
 
  cleanup:
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	strbuf_release(&ref_name);
 	strbuf_release(&err);
 }

diff --git a/refs.c b/refs.c
index 150c980..f0f0d23 100644
--- a/refs.c
+++ b/refs.c

@@ -26,7 +26,7 @@ static unsigned char refname_disposition[256] = {
 };
 
 /*
- * Used as a flag to ref_transaction_delete when a loose ref is being
+ * Used as a flag to transaction_delete_ref when a loose ref is being
  * pruned.
  */
 #define REF_ISPRUNING	0x0100

@@ -2533,23 +2533,23 @@ static void try_remove_empty_parents(char *name)
 /* make sure nobody touched the ref, and unlink */
 static void prune_ref(struct ref_to_prune *r)
 {
-	struct ref_transaction *transaction;
+	struct transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 
 	if (check_refname_format(r->name, 0))
 		return;
 
-	transaction = ref_transaction_begin(&err);
+	transaction = transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_delete(transaction, r->name, r->sha1,
+	    transaction_delete_ref(transaction, r->name, r->sha1,
 				   REF_ISPRUNING, 1, NULL, &err) ||
-	    ref_transaction_commit(transaction, &err)) {
-		ref_transaction_free(transaction);
+	    transaction_commit(transaction, &err)) {
+		transaction_free(transaction);
 		error("%s", err.buf);
 		strbuf_release(&err);
 		return;
 	}
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	strbuf_release(&err);
 	try_remove_empty_parents(r->name);
 }

@@ -2711,20 +2711,20 @@ static int delete_ref_loose(struct ref_lock *lock, int flag, struct strbuf *err)
 
 int delete_ref(const char *refname, const unsigned char *sha1, int delopt)
 {
-	struct ref_transaction *transaction;
+	struct transaction *transaction;
 	struct strbuf err = STRBUF_INIT;
 
-	transaction = ref_transaction_begin(&err);
+	transaction = transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_delete(transaction, refname, sha1, delopt,
+	    transaction_delete_ref(transaction, refname, sha1, delopt,
 				   sha1 && !is_null_sha1(sha1), NULL, &err) ||
-	    ref_transaction_commit(transaction, &err)) {
+	    transaction_commit(transaction, &err)) {
 		error("%s", err.buf);
-		ref_transaction_free(transaction);
+		transaction_free(transaction);
 		strbuf_release(&err);
 		return 1;
 	}
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	strbuf_release(&err);
 	return 0;
 }

@@ -3543,9 +3543,9 @@ struct ref_update {
  *         an active transaction or if there is a failure while building
  *         the transaction thus rendering it failed/inactive.
  */
-enum ref_transaction_state {
-	REF_TRANSACTION_OPEN   = 0,
-	REF_TRANSACTION_CLOSED = 1
+enum transaction_state {
+	TRANSACTION_OPEN   = 0,
+	TRANSACTION_CLOSED = 1
 };
 
 /*

@@ -3553,21 +3553,21 @@ enum ref_transaction_state {
  * consist of checks and updates to multiple references, carried out
  * as atomically as possible.  This structure is opaque to callers.
  */
-struct ref_transaction {
+struct transaction {
 	struct ref_update **updates;
 	size_t alloc;
 	size_t nr;
-	enum ref_transaction_state state;
+	enum transaction_state state;
 };
 
-struct ref_transaction *ref_transaction_begin(struct strbuf *err)
+struct transaction *transaction_begin(struct strbuf *err)
 {
 	assert(err);
 
-	return xcalloc(1, sizeof(struct ref_transaction));
+	return xcalloc(1, sizeof(struct transaction));
 }
 
-void ref_transaction_free(struct ref_transaction *transaction)
+void transaction_free(struct transaction *transaction)
 {
 	int i;

@@ -3582,7 +3582,7 @@ void ref_transaction_free(struct ref_transaction *transaction)
 	free(transaction);
 }
 
-static struct ref_update *add_update(struct ref_transaction *transaction,
+static struct ref_update *add_update(struct transaction *transaction,
 				     const char *refname)
 {
 	size_t len = strlen(refname);

@@ -3594,7 +3594,7 @@ static struct ref_update *add_update(struct ref_transaction *transaction,
 	return update;
 }
 
-int ref_transaction_update(struct ref_transaction *transaction,
+int transaction_update_ref(struct transaction *transaction,
 			   const char *refname,
 			   const unsigned char *new_sha1,
 			   const unsigned char *old_sha1,

@@ -3605,7 +3605,7 @@ int ref_transaction_update(struct ref_transaction *transaction,
 
 	assert(err);
 
-	if (transaction->state != REF_TRANSACTION_OPEN)
+	if (transaction->state != TRANSACTION_OPEN)
 		die("BUG: update called for transaction that is not open");
 
 	if (have_old && !old_sha1)

@@ -3629,23 +3629,23 @@ int ref_transaction_update(struct ref_transaction *transaction,
 	return 0;
 }
 
-int ref_transaction_create(struct ref_transaction *transaction,
+int transaction_create_ref(struct transaction *transaction,
 			   const char *refname,
 			   const unsigned char *new_sha1,
 			   int flags, const char *msg,
 			   struct strbuf *err)
 {
-	return ref_transaction_update(transaction, refname, new_sha1,
+	return transaction_update_ref(transaction, refname, new_sha1,
 				      null_sha1, flags, 1, msg, err);
 }
 
-int ref_transaction_delete(struct ref_transaction *transaction,
+int transaction_delete_ref(struct transaction *transaction,
 			   const char *refname,
 			   const unsigned char *old_sha1,
 			   int flags, int have_old, const char *msg,
 			   struct strbuf *err)
 {
-	return ref_transaction_update(transaction, refname, null_sha1,
+	return transaction_update_ref(transaction, refname, null_sha1,
 				      old_sha1, flags, have_old, msg, err);
 }

@@ -3653,17 +3653,17 @@ int update_ref(const char *action, const char *refname,
 	       const unsigned char *sha1, const unsigned char *oldval,
 	       int flags, enum action_on_err onerr)
 {
-	struct ref_transaction *t;
+	struct transaction *t;
 	struct strbuf err = STRBUF_INIT;
 
-	t = ref_transaction_begin(&err);
+	t = transaction_begin(&err);
 	if (!t ||
-	    ref_transaction_update(t, refname, sha1, oldval, flags,
+	    transaction_update_ref(t, refname, sha1, oldval, flags,
 				   !!oldval, action, &err) ||
-	    ref_transaction_commit(t, &err)) {
+	    transaction_commit(t, &err)) {
 		const char *str = "update_ref failed for ref '%s': %s";
 
-		ref_transaction_free(t);
+		transaction_free(t);
 		switch (onerr) {
 		case UPDATE_REFS_MSG_ON_ERR:
 			error(str, refname, err.buf);

@@ -3678,7 +3678,7 @@ int update_ref(const char *action, const char *refname,
 		return 1;
 	}
 	strbuf_release(&err);
-	ref_transaction_free(t);
+	transaction_free(t);
 	return 0;
 }

@@ -3706,8 +3706,8 @@ static int ref_update_reject_duplicates(struct ref_update **updates, int n,
 	return 0;
 }
 
-int ref_transaction_commit(struct ref_transaction *transaction,
-			   struct strbuf *err)
+int transaction_commit(struct transaction *transaction,
+		       struct strbuf *err)
 {
 	int ret = 0, delnum = 0, i;
 	const char **delnames;

@@ -3716,11 +3716,11 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 
 	assert(err);
 
-	if (transaction->state != REF_TRANSACTION_OPEN)
+	if (transaction->state != TRANSACTION_OPEN)
 		die("BUG: commit called for transaction that is not open");
 
 	if (!n) {
-		transaction->state = REF_TRANSACTION_CLOSED;
+		transaction->state = TRANSACTION_CLOSED;
 		return 0;
 	}

@@ -3799,7 +3799,7 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 	clear_loose_ref_cache(&ref_cache);
 
 cleanup:
-	transaction->state = REF_TRANSACTION_CLOSED;
+	transaction->state = TRANSACTION_CLOSED;
 
 	for (i = 0; i < n; i++)
 		if (updates[i]->lock)

diff --git a/refs.h b/refs.h
index 7d675b7..556adfd 100644
--- a/refs.h
+++ b/refs.h

@@ -11,22 +11,22 @@ struct ref_lock {
 };
 
 /*
- * A ref_transaction represents a collection of ref updates
+ * A transaction represents a collection of ref updates
  * that should succeed or fail together.
  *
  * Calling sequence
  * ----------------
- * - Allocate and initialize a `struct ref_transaction` by calling
- *   `ref_transaction_begin()`.
+ * - Allocate and initialize a `struct transaction` by calling
+ *   `transaction_begin()`.
  *
  * - List intended ref updates by calling functions like
- *   `ref_transaction_update()` and `ref_transaction_create()`.
+ *   `transaction_update_ref()` and `transaction_create_ref()`.
  *
- * - Call `ref_transaction_commit()` to execute the transaction.
+ * - Call `transaction_commit()` to execute the transaction.
  *   If this succeeds, the ref updates will have taken place and
  *   the transaction cannot be rolled back.
  *
- * - At any time call `ref_transaction_free()` to discard the
+ * - At any time call `transaction_free()` to discard the
  *   transaction and free associated resources.  In particular,
  *   this rolls back the transaction if it has not been
  *   successfully committed.

@@ -42,7 +42,7 @@ struct ref_lock {
  * The message is appended to err without first clearing err.
  * err will not be '\n' terminated.
  */
-struct ref_transaction;
+struct transaction;
 
 /*
  * Bit values set in the flags argument passed to each_ref_fn():

@@ -181,8 +181,8 @@ extern int is_branch(const char *refname);
 extern int peel_ref(const char *refname, unsigned char *sha1);
 
 /*
- * Flags controlling lock_any_ref_for_update(), ref_transaction_update(),
- * ref_transaction_create(), etc.
+ * Flags controlling lock_any_ref_for_update(), transaction_update_ref(),
+ * transaction_create_ref(), etc.
  * REF_NODEREF: act on the ref directly, instead of dereferencing
  *              symbolic references.
  * REF_DELETING: tolerate broken refs

@@ -269,13 +269,13 @@ enum action_on_err {
 
 /*
  * Begin a reference transaction.  The reference transaction must
- * be freed by calling ref_transaction_free().
+ * be freed by calling transaction_free().
  */
-struct ref_transaction *ref_transaction_begin(struct strbuf *err);
+struct transaction *transaction_begin(struct strbuf *err);
 
 /*
  * The following functions add a reference check or update to a
- * ref_transaction.  In all of them, refname is the name of the
+ * transaction.  In all of them, refname is the name of the
  * reference to be affected.  The functions make internal copies of
  * refname and msg, so the caller retains ownership of these parameters.
  * flags can be REF_NODEREF; it is passed to update_ref_lock().

@@ -291,7 +291,7 @@ struct ref_transaction *ref_transaction_begin(struct strbuf *err);
  * means that the transaction as a whole has failed and will need to be
  * rolled back.
  */
-int ref_transaction_update(struct ref_transaction *transaction,
+int transaction_update_ref(struct transaction *transaction,
 			   const char *refname,
 			   const unsigned char *new_sha1,
 			   const unsigned char *old_sha1,

@@ -307,7 +307,7 @@ int ref_transaction_update(struct ref_transaction *transaction,
  * means that the transaction as a whole has failed and will need to be
  * rolled back.
  */
-int ref_transaction_create(struct ref_transaction *transaction,
+int transaction_create_ref(struct transaction *transaction,
 			   const char *refname,
 			   const unsigned char *new_sha1,
 			   int flags, const char *msg,

@@ -321,7 +321,7 @@ int ref_transaction_create(struct ref_transaction *transaction,
  * means that the transaction as a whole has failed and will need to be
  * rolled back.
  */
-int ref_transaction_delete(struct ref_transaction *transaction,
+int transaction_delete_ref(struct transaction *transaction,
 			   const char *refname,
 			   const unsigned char *old_sha1,
 			   int flags, int have_old, const char *msg,

@@ -337,13 +337,13 @@ int ref_transaction_delete(struct ref_transaction *transaction,
 #define TRANSACTION_NAME_CONFLICT -1
 /* All other errors. */
 #define TRANSACTION_GENERIC_ERROR -2
-int ref_transaction_commit(struct ref_transaction *transaction,
-			   struct strbuf *err);
+int transaction_commit(struct transaction *transaction,
+		       struct strbuf *err);
 
 /*
  * Free an existing transaction and all associated data.
  */
-void ref_transaction_free(struct ref_transaction *transaction);
+void transaction_free(struct transaction *transaction);
 
 /** Lock a ref and then write its file */
 int update_ref(const char *action, const char *refname,

diff --git a/sequencer.c b/sequencer.c
index a03d4fa..f888005 100644
--- a/sequencer.c
+++ b/sequencer.c

@@ -238,7 +238,7 @@ static int error_dirty_index(struct replay_opts *opts)
 static int fast_forward_to(const unsigned char *to, const unsigned char *from,
 			int unborn, struct replay_opts *opts)
 {
-	struct ref_transaction *transaction;
+	struct transaction *transaction;
 	struct strbuf sb = STRBUF_INIT;
 	struct strbuf err = STRBUF_INIT;

@@ -248,13 +248,13 @@ static int fast_forward_to(const unsigned char *to, const unsigned char *from,
 
 	strbuf_addf(&sb, "%s: fast-forward", action_name(opts));
 
-	transaction = ref_transaction_begin(&err);
+	transaction = transaction_begin(&err);
 	if (!transaction ||
-	    ref_transaction_update(transaction, "HEAD",
+	    transaction_update_ref(transaction, "HEAD",
 				   to, unborn ? null_sha1 : from,
 				   0, 1, sb.buf, &err) ||
-	    ref_transaction_commit(transaction, &err)) {
-		ref_transaction_free(transaction);
+	    transaction_commit(transaction, &err)) {
+		transaction_free(transaction);
 		error("%s", err.buf);
 		strbuf_release(&sb);
 		strbuf_release(&err);

@@ -263,7 +263,7 @@ static int fast_forward_to(const unsigned char *to, const unsigned char *from,
 
 	strbuf_release(&sb);
 	strbuf_release(&err);
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	return 0;
 }

diff --git a/walker.c b/walker.c
index f149371..f1d5e9b 100644
--- a/walker.c
+++ b/walker.c

@@ -253,7 +253,7 @@ int walker_fetch(struct walker *walker, int targets, char **target,
 {
 	struct strbuf refname = STRBUF_INIT;
 	struct strbuf err = STRBUF_INIT;
-	struct ref_transaction *transaction = NULL;
+	struct transaction *transaction = NULL;
 	unsigned char *sha1 = xmalloc(targets * 20);
 	char *msg = NULL;
 	int i, ret = -1;

@@ -261,7 +261,7 @@ int walker_fetch(struct walker *walker, int targets, char **target,
 	save_commit_buffer = 0;
 
 	if (write_ref) {
-		transaction = ref_transaction_begin(&err);
+		transaction = transaction_begin(&err);
 		if (!transaction) {
 			error("%s", err.buf);
 			goto done;

@@ -298,7 +298,7 @@ int walker_fetch(struct walker *walker, int targets, char **target,
 			continue;
 		strbuf_reset(&refname);
 		strbuf_addf(&refname, "refs/%s", write_ref[i]);
-		if (ref_transaction_update(transaction, refname.buf,
+		if (transaction_update_ref(transaction, refname.buf,
 					   &sha1[20 * i], NULL, 0, 0,
 					   msg ? msg : "fetch (unknown)",
 					   &err)) {

@@ -306,7 +306,7 @@ int walker_fetch(struct walker *walker, int targets, char **target,
 			goto done;
 		}
 	}
-	if (ref_transaction_commit(transaction, &err)) {
+	if (transaction_commit(transaction, &err)) {
 		error("%s", err.buf);
 		goto done;
 	}

@@ -314,7 +314,7 @@ int walker_fetch(struct walker *walker, int targets, char **target,
 	ret = 0;
 
 done:
-	ref_transaction_free(transaction);
+	transaction_free(transaction);
 	free(msg);
 	free(sha1);
 	strbuf_release(&err);

-- 
2.2.0.rc3

[PATCH 3/4] refs.c: add a transaction function to append a reflog entry

From: Stefan Beller <hidden>
Date: 2016-06-15 23:03:07

From: Ronnie Sahlberg <redacted>

Define a new transaction update type, UPDATE_LOG, and a new function
transaction_update_reflog. This function will lock the reflog and append
an entry to it during transaction commit. We can pass a flag to this
function, which can truncate the the reflog file before we write the
update.

When performing a reflog transaction update, only write to the reflog iff
msg is non-NULL. This can then be combined with REFLOG_TRUNCATE to perform
an update that only truncates but does not write. This change only affects
whether or not a reflog entry should be generated and written. If msg == NULL
then no such entry will be written.

Orthogonal to this we have a boolean flag REFLOG_TRUNCATE which is used to
tell the transaction system to "truncate the reflog and thus discard all
previous users".

At the current time the only place where we use msg == NULL is also the
place, where we use REFLOG_TRUNCATE. Even though these two settings are
currently only ever used together it still makes sense to have them through
two separate knobs.

This allows future consumers of this API that may want to do things
differently. For example someone can do:
  msg="Reflog truncated by Bob because ..." + REFLOG_TRUNCATE
and have it truncate the log and have it start fresh with an initial message
that explains the log was truncated. This API allows that.

During one transaction we allow to make multiple reflog updates to the
same ref. This means we only need to lock the reflog once, during the first
update that touches the reflog, and that all further updates can just write the
reflog entry since the reflog is already locked.

This allows us to write code (internally in refs.c) such as:

t = transaction_begin()
transaction_reflog_update(t, "foo", REFLOG_TRUNCATE, NULL);
loop-over-something...
   transaction_reflog_update(t, "foo", 0, <message>);
transaction_commit(t)

where we first truncate the reflog and then build the new content one line
at a time.

While this technically looks like O(n2) behavior it is not that bad.
We only do this loop for transactions that cover a single ref during
reflog expire. This means that the linear search inside
transaction_update_reflog() will find the match on the very first entry
thus making it O(1) and not O(n) or our usecases. Thus the whole expire
becomes O(n) instead of O(n2). If in the future we start doing this for many
refs in one single transaction we might want to optimize this.
But there is no need to complexify the code and optimize for future usecases
that might never materialize at this stage.

Instead of recording the line by line reflog updates in memory, use a
tempfile: .git/tmp_reflog_XXXXXX which we write the entries to as the
transaction is built. Then just rename this file onto the destination
reflog file when the transaction is committed.

todo:
This patch needs to add an atexit() thingy as well to ensure that
any remaining files are unlinked on exit, just like the lock_file() thing does.

Signed-off-by: Ronnie Sahlberg <redacted>
Signed-off-by: Stefan Beller <redacted>
---

This is a complete rewrite from previous series. Sorry no diff to previous versions.

 refs.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 refs.h |  21 ++++++++++
 2 files changed, 167 insertions(+), 2 deletions(-)

diff --git a/refs.c b/refs.c
index 84e086f..a1af703 100644
--- a/refs.c
+++ b/refs.c

@@ -3517,7 +3517,8 @@ int for_each_reflog(each_ref_fn fn, void *cb_data)
 }
 
 enum transaction_update_type {
-	UPDATE_SHA1 = 0
+	UPDATE_SHA1 = 0,
+	UPDATE_LOG = 1
 };
 
 /**

@@ -3530,11 +3531,18 @@ struct ref_update {
 	enum transaction_update_type update_type;
 	unsigned char new_sha1[20];
 	unsigned char old_sha1[20];
-	int flags; /* REF_NODEREF? */
+	int flags;  /* The flags to transaction_update_ref[log] are defined
+		     * in refs.h
+		     */
 	int have_old; /* 1 if old_sha1 is valid, 0 otherwise */
 	struct ref_lock *lock;
 	int type;
 	char *msg;
+
+	/* used by reflog updates */
+	char *tmp_reflog;
+	int reflog_fd;
+
 	const char refname[FLEX_ARRAY];
 };

@@ -3580,6 +3588,7 @@ void transaction_free(struct transaction *transaction)
 		return;
 
 	for (i = 0; i < transaction->nr; i++) {
+		free(transaction->updates[i]->tmp_reflog);
 		free(transaction->updates[i]->msg);
 		free(transaction->updates[i]);
 	}

@@ -3601,6 +3610,116 @@ static struct ref_update *add_update(struct transaction *transaction,
 	return update;
 }
 
+int transaction_update_reflog(struct transaction *transaction,
+			      const char *refname,
+			      const unsigned char *new_sha1,
+			      const unsigned char *old_sha1,
+			      const char *email,
+			      unsigned long timestamp, int tz,
+			      const char *msg, int flags,
+			      struct strbuf *err)
+{
+	struct ref_update *update;
+	struct strbuf buf = STRBUF_INIT;
+	int i;
+
+	if (transaction->state != TRANSACTION_OPEN)
+		die("BUG: update_reflog called for transaction that is not open");
+
+	/* Check if there is another reflog update for this ref already. */
+	for (i = 0; transaction->nr > 0 && i < transaction->nr; i++) {
+		if (transaction->updates[i]->update_type != UPDATE_LOG)
+			continue;
+		if (!strcmp(transaction->updates[i]->refname,
+			    refname)) {
+			break;
+		}
+	}
+	/* When starting the transaction or when we did not find the ref,
+	 * we will need to create a new temporary file. */
+	if (transaction->nr == 0 || i == transaction->nr) {
+		int orig_fd;
+		update = add_update(transaction, refname, UPDATE_LOG);
+
+		orig_fd = open(git_path("logs/%s", refname), O_RDONLY);
+		if (orig_fd < 0) {
+			const char *str = "Cannot open reflog for '%s'. %s";
+
+			strbuf_addf(err, str, refname, strerror(errno));
+			transaction->state = TRANSACTION_CLOSED;
+			return 1;
+		}
+
+		update->tmp_reflog = xstrdup(git_path(".tmp_reflog_XXXXXX"));
+		update->reflog_fd = mkstemp(update->tmp_reflog);
+		if (update->reflog_fd == -1) {
+			const char *str = "Could not create temporary "
+			  "reflog for '%s'. %s";
+
+			close(orig_fd);
+			strbuf_addf(err, str, refname, strerror(errno));
+			transaction->state = TRANSACTION_CLOSED;
+			return 1;
+		}
+		if (adjust_shared_perm(update->tmp_reflog)) {
+			strbuf_addf(err, "Could not fix permission bits for "
+				    "reflog: %s. %s",
+				    update->tmp_reflog, strerror(errno));
+			close(orig_fd);
+			unlink_or_warn(update->tmp_reflog);
+			close(update->reflog_fd);
+			update->reflog_fd = -1;
+			transaction->state = TRANSACTION_CLOSED;
+			return 1;
+		}
+		if (copy_fd(orig_fd, update->reflog_fd)) {
+			strbuf_addf(err, "Could not copy reflog: %s. %s",
+				    refname, strerror(errno));
+			close(orig_fd);
+			unlink_or_warn(update->tmp_reflog);
+			close(update->reflog_fd);
+			update->reflog_fd = -1;
+			transaction->state = TRANSACTION_CLOSED;
+			return 1;
+		}
+		close(orig_fd);
+	} else {
+		update = transaction->updates[i];
+	}
+
+	if (flags & REFLOG_TRUNCATE) {
+		if (lseek(update->reflog_fd, 0, SEEK_SET) < 0 ||
+			ftruncate(update->reflog_fd, 0)) {
+			strbuf_addf(err, "Could not truncate reflog: %s. %s",
+				    refname, strerror(errno));
+			unlink_or_warn(update->tmp_reflog);
+			close(update->reflog_fd);
+			update->reflog_fd = -1;
+			transaction->state = TRANSACTION_CLOSED;
+			return 1;
+		}
+	}
+	if (email)
+		strbuf_addf(&buf, "%s %lu %+05d", email, timestamp, tz);
+
+	if (msg &&
+	    log_ref_write_fd(update->reflog_fd,
+			     old_sha1, new_sha1,
+			     buf.buf, msg)) {
+		strbuf_addf(err, "Could not write to reflog: %s. %s",
+			    refname, strerror(errno));
+		unlink_or_warn(update->tmp_reflog);
+		close(update->reflog_fd);
+		update->reflog_fd = -1;
+		transaction->state = TRANSACTION_CLOSED;
+		strbuf_release(&buf);
+		return 1;
+	}
+	strbuf_release(&buf);
+
+	return 0;
+}
+
 int transaction_update_ref(struct transaction *transaction,
 			   const char *refname,
 			   const unsigned char *new_sha1,

@@ -3815,6 +3934,31 @@ int transaction_commit(struct transaction *transaction,
 	}
 	for (i = 0; i < delnum; i++)
 		unlink_or_warn(git_path("logs/%s", delnames[i]));
+
+	/* Commit all reflog files */
+	for (i = 0; i < n; i++) {
+		struct ref_update *update = updates[i];
+
+		if (update->update_type != UPDATE_LOG)
+			continue;
+		if (update->reflog_fd == -1)
+			continue;
+		if (close(update->reflog_fd) == -1) {
+			error("Could not commit temporary reflog: %s. %s",
+			      update->refname, strerror(errno));
+			update->reflog_fd = -1;
+			continue;
+		}
+		update->reflog_fd = -1;
+		if (rename(update->tmp_reflog,
+			   git_path("logs/%s", update->refname))) {
+			error("Could not commit reflog: %s. %s",
+			      update->refname, strerror(errno));
+			update->reflog_fd = -1;
+			continue;
+		}
+	}
+
 	clear_loose_ref_cache(&ref_cache);
 
 cleanup:

diff --git a/refs.h b/refs.h
index 556adfd..9f70b89 100644
--- a/refs.h
+++ b/refs.h

@@ -328,6 +328,27 @@ int transaction_delete_ref(struct transaction *transaction,
 			   struct strbuf *err);
 
 /*
+ * Flags controlling transaction_update_reflog().
+ * REFLOG_TRUNCATE: Truncate the reflog.
+ *
+ * Flags >= 0x100 are reserved for internal use.
+ */
+#define REFLOG_TRUNCATE 0x01
+/*
+ * Append a reflog entry for refname. If the REFLOG_TRUNCATE flag is set
+ * this update will first truncate the reflog before writing the entry.
+ * If msg is NULL no update will be written to the log.
+ */
+int transaction_update_reflog(struct transaction *transaction,
+			      const char *refname,
+			      const unsigned char *new_sha1,
+			      const unsigned char *old_sha1,
+			      const char *email,
+			      unsigned long timestamp, int tz,
+			      const char *msg, int flags,
+			      struct strbuf *err);
+
+/*
  * Commit all of the changes that have been queued in transaction, as
  * atomically as possible.
  *

-- 
2.2.0.rc3

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