From 8280bbebd1ecc4633b969a439ed4ca653d1bc958 Mon Sep 17 00:00:00 2001
From: Michael Haggerty <mhagger@alum.mit.edu>
Date: Mon, 2 Mar 2015 10:29:51 +0100
Subject: write_ref_sha1(): remove check for lock == NULL

None of the callers pass NULL to this function, and there doesn't seem
to be any usefulness to allowing them to do so.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/refs.c b/refs.c
index c5fa709..d1130e2 100644
--- a/refs.c
+++ b/refs.c
@@ -3080,10 +3080,6 @@ 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;
-- 
cgit v0.10.2-6-g49f6


From 706d5f816fbcb1299c19f4d41bea60f1e229165e Mon Sep 17 00:00:00 2001
From: Michael Haggerty <mhagger@alum.mit.edu>
Date: Mon, 2 Mar 2015 10:29:52 +0100
Subject: write_ref_sha1(): move write elision test to callers

write_ref_sha1() previously skipped the write if the reference already
had the desired value, unless lock->force_write was set. Instead,
perform that test at the callers.

Two of the callers (in rename_ref()) unconditionally set force_write
just before calling write_ref_sha1(), so they don't need the extra
check at all. Nor do they need to set force_write anymore.

The last caller, in ref_transaction_commit(), still needs the test.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/refs.c b/refs.c
index d1130e2..651e37e 100644
--- a/refs.c
+++ b/refs.c
@@ -2878,7 +2878,6 @@ 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);
@@ -2894,7 +2893,6 @@ 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))
@@ -3080,10 +3078,6 @@ static int write_ref_sha1(struct ref_lock *lock,
 	static char term = '\n';
 	struct object *o;
 
-	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",
@@ -3797,15 +3791,21 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 		struct ref_update *update = updates[i];
 
 		if (!is_null_sha1(update->new_sha1)) {
-			if (write_ref_sha1(update->lock, update->new_sha1,
-					   update->msg)) {
+			if (!update->lock->force_write &&
+			    !hashcmp(update->lock->old_sha1, update->new_sha1)) {
+				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 */
 		}
 	}
 
-- 
cgit v0.10.2-6-g49f6


From 074336e5ed4ff10577f22c6812e092e3f6607405 Mon Sep 17 00:00:00 2001
From: Michael Haggerty <mhagger@alum.mit.edu>
Date: Mon, 2 Mar 2015 10:29:53 +0100
Subject: lock_ref_sha1_basic(): do not set force_write for missing references

If a reference is missing, its SHA-1 will be null_sha1, which can't
possibly match a new value that ref_transaction_commit() is trying to
update it to. So there is no need to set force_write in this scenario.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/refs.c b/refs.c
index 651e37e..b6a2535 100644
--- a/refs.c
+++ b/refs.c
@@ -2259,7 +2259,6 @@ 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));
@@ -2298,13 +2297,13 @@ 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;
@@ -2320,8 +2319,6 @@ 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;
 
-- 
cgit v0.10.2-6-g49f6


From 5a6f47077b31be45bfadd6cef3b8b1a79ad57de5 Mon Sep 17 00:00:00 2001
From: Stefan Beller <sbeller@google.com>
Date: Tue, 3 Mar 2015 12:43:14 +0100
Subject: struct ref_lock: delete the force_write member

Instead, compute the value when it is needed.

Signed-off-by: Stefan Beller <sbeller@google.com>
Edited-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/refs.c b/refs.c
index b6a2535..5d8d57d 100644
--- a/refs.c
+++ b/refs.c
@@ -12,7 +12,6 @@ struct ref_lock {
 	struct lock_file *lk;
 	unsigned char old_sha1[20];
 	int lock_fd;
-	int force_write;
 };
 
 /*
@@ -2319,8 +2318,6 @@ 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 ((flags & REF_NODEREF) && (type & REF_ISSYMREF))
-		lock->force_write = 1;
 
  retry:
 	switch (safe_create_leading_directories(ref_file)) {
@@ -3788,8 +3785,15 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 		struct ref_update *update = updates[i];
 
 		if (!is_null_sha1(update->new_sha1)) {
-			if (!update->lock->force_write &&
-			    !hashcmp(update->lock->old_sha1, update->new_sha1)) {
+			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,
-- 
cgit v0.10.2-6-g49f6


From fe2a18165c97d3e0937bb99fda449e1f64e5c867 Mon Sep 17 00:00:00 2001
From: Michael Haggerty <mhagger@alum.mit.edu>
Date: Tue, 3 Mar 2015 12:43:15 +0100
Subject: reflog: improve and update documentation

Revamp the "git reflog" usage documentation in the manpage and the
command help to match the current reality and improve its clarity:

* Add documentation for some options that had been left out.

* Group the subcommands and options more logically and move more
  common subcommands/options higher.

* Improve some explanations.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-reflog.txt b/Documentation/git-reflog.txt
index 70791b9..730106c 100644
--- a/Documentation/git-reflog.txt
+++ b/Documentation/git-reflog.txt
@@ -17,85 +17,112 @@ 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.
 
 --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
diff --git a/builtin/reflog.c b/builtin/reflog.c
index 49c64f9..8182b64 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c
@@ -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;
-- 
cgit v0.10.2-6-g49f6


From 5e6f003ca8aed546d50a4f3fbf1e011186047bc0 Mon Sep 17 00:00:00 2001
From: Michael Haggerty <mhagger@alum.mit.edu>
Date: Tue, 3 Mar 2015 12:43:16 +0100
Subject: reflog_expire(): ignore --updateref for symbolic references

If we are expiring reflog entries for a symbolic reference, then how
should --updateref be handled if the newest reflog entry is expired?

Option 1: Update the referred-to reference. (This is what the current
code does.) This doesn't make sense, because the referred-to reference
has its own reflog, which hasn't been rewritten.

Option 2: Update the symbolic reference itself (as in, REF_NODEREF).
This would convert the symbolic reference into a non-symbolic
reference (e.g., detaching HEAD), which is surely not what a user
would expect.

Option 3: Error out. This is plausible, but it would make the
following usage impossible:

    git reflog expire ... --updateref --all

Option 4: Ignore --updateref for symbolic references.

We choose to implement option 4.

Note: another problem in this code will be fixed in a moment.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/git-reflog.txt b/Documentation/git-reflog.txt
index 730106c..5e7908e 100644
--- a/Documentation/git-reflog.txt
+++ b/Documentation/git-reflog.txt
@@ -88,7 +88,8 @@ Options for `expire`
 
 --updateref::
 	Update the reference to the value of the top reflog entry (i.e.
-	<ref>@\{0\}) if the previous top entry was pruned.
+	<ref>@\{0\}) if the previous top entry was pruned.  (This
+	option is ignored for symbolic references.)
 
 --rewrite::
 	If a reflog entry's predecessor is pruned, adjust its "old"
diff --git a/refs.c b/refs.c
index 5d8d57d..4684ffe 100644
--- a/refs.c
+++ b/refs.c
@@ -4029,6 +4029,7 @@ 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;
@@ -4040,7 +4041,7 @@ 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)) {
@@ -4077,10 +4078,18 @@ 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.
+		 */
+		int update = (flags & EXPIRE_REFLOGS_UPDATE_REF) &&
+			!(type & REF_ISSYMREF);
+
 		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 ||
@@ -4091,7 +4100,7 @@ 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);
 		}
 	}
-- 
cgit v0.10.2-6-g49f6


From 423c688b855c328ecda0b6a79c4b1af78d09a10c Mon Sep 17 00:00:00 2001
From: Michael Haggerty <mhagger@alum.mit.edu>
Date: Tue, 3 Mar 2015 12:43:17 +0100
Subject: reflog_expire(): never update a reference to null_sha1

Currently, if --updateref is specified and the very last reflog entry
is expired or deleted, the reference's value is set to 0{40}. This is
an invalid state of the repository, and breaks, for example, "git
fsck" and "git for-each-ref".

The only place we use --updateref in our own code is when dropping
stash entries. In that code, the very next step is to check if the
reflog has been made empty, and if so, delete the "refs/stash"
reference entirely. Thus that code path ultimately leaves the
repository in a valid state.

But we don't want to the repository in an invalid state even
temporarily, and we don't want to leave an invalid state if other
callers of "git reflog expire|delete --updateref" don't think to do
the extra cleanup step.

So, if "git reflog expire|delete" leaves no more entries in the
reflog, just leave the reference unchanged.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/refs.c b/refs.c
index 4684ffe..05a4be0 100644
--- a/refs.c
+++ b/refs.c
@@ -4081,10 +4081,13 @@ int reflog_expire(const char *refname, const unsigned char *sha1,
 		/*
 		 * 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.
+		 * 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);
+			!(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,
-- 
cgit v0.10.2-6-g49f6