Merge branch 'sp/reflog'

* sp/reflog:
  fetch.c: do not pass uninitialized lock to unlock_ref().
  Test that git-branch -l works.
  Verify git-commit provides a reflog message.
  Enable ref log creation in git checkout -b.
  Create/delete branch ref logs.
  Include ref log detail in commit, reset, etc.
  Change order of -m option to update-ref.
  Correct force_write bug in refs.c
  Change 'master@noon' syntax to 'master@{noon}'.
  Log ref updates made by fetch.
  Force writing ref if it doesn't exist.
  Added logs/ directory to repository layout.
  General ref log reading improvements.
  Fix ref log parsing so it works properly.
  Support 'master@2 hours ago' syntax
  Log ref updates to logs/refs/<ref>
  Convert update-ref to use ref_lock API.
  Improve abstraction of ref lock/write.

Documentation/config.txt

@@ -70,6 +70,14 @@ core.preferSymlinkRefs::
 	This is sometimes needed to work with old scripts that
 	expect HEAD to be a symbolic link.
 
+core.logAllRefUpdates::
+	If true, `git-update-ref` will append a line to
+	"$GIT_DIR/logs/<ref>" listing the new SHA1 and the date/time
+	of the update.	If the file does not exist it will be
+	created automatically.	This information can be used to
+	determine what commit was the tip of a branch "2 days ago".
+	This value is false by default (no logging).
+
 core.repositoryFormatVersion::
 	Internal variable identifying the repository format and layout
 	version.

Documentation/git-branch.txt

@@ -9,7 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git-branch' [-r]
-'git-branch' [-f] <branchname> [<start-point>]
+'git-branch' [-l] [-f] <branchname> [<start-point>]
 'git-branch' (-d | -D) <branchname>...
 
 DESCRIPTION
@@ -23,7 +23,8 @@ If no <start-point> is given, the branch will be created with a head
 equal to that of the currently checked out branch.
 
 With a `-d` or `-D` option, `<branchname>` will be deleted.  You may
-specify more than one branch for deletion.
+specify more than one branch for deletion.  If the branch currently
+has a ref log then the ref log will also be deleted.
 
 
 OPTIONS
@@ -34,6 +35,11 @@ OPTIONS
 -D::
 	Delete a branch irrespective of its index status.
 
+-l::
+	Create the branch's ref log.  This activates recording of
+	all changes to made the branch ref, enabling use of date
+	based sha1 expressions such as "<branchname>@{yesterday}".
+
 -f::
 	Force the creation of a new branch even if it means deleting
 	a branch that already exists with the same name.

Documentation/git-checkout.txt

@@ -8,7 +8,7 @@ git-checkout - Checkout and switch to a branch
 SYNOPSIS
 --------
 [verse]
-'git-checkout' [-f] [-b <new_branch>] [-m] [<branch>]
+'git-checkout' [-f] [-b <new_branch> [-l]] [-m] [<branch>]
 'git-checkout' [-m] [<branch>] <paths>...
 
 DESCRIPTION
@@ -40,6 +40,11 @@ OPTIONS
 	by gitlink:git-check-ref-format[1].  Some of these checks
 	may restrict the characters allowed in a branch name.
 
+-l::
+	Create the new branch's ref log.  This activates recording of
+	all changes to made the branch ref, enabling use of date
+	based sha1 expressions such as "<branchname>@{yesterday}".
+
 -m::
 	If you have local modifications to one or more files that
 	are different between the current branch and the branch to

Documentation/git-rev-parse.txt

@@ -124,6 +124,13 @@ syntax.
   happen to have both heads/master and tags/master, you can
   explicitly say 'heads/master' to tell git which one you mean.
 
+* A suffix '@' followed by a date specification enclosed in a brace
+  pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
+  second ago\}' or '\{1979-02-26 18:30:00\}') to specify the value
+  of the ref at a prior point in time.  This suffix may only be
+  used immediately following a ref name and the ref must have an
+  existing log ($GIT_DIR/logs/<ref>).
+
 * A suffix '{caret}' to a revision parameter means the first parent of
   that commit object.  '{caret}<n>' means the <n>th parent (i.e.
   'rev{caret}'

Documentation/git-update-ref.txt

@@ -7,7 +7,7 @@ git-update-ref - update the object name stored in a ref safely
 
 SYNOPSIS
 --------
-'git-update-ref' <ref> <newvalue> [<oldvalue>]
+'git-update-ref' [-m <reason>] <ref> <newvalue> [<oldvalue>]
 
 DESCRIPTION
 -----------
@@ -49,6 +49,32 @@ for reading but not for writing (so we'll never write through a
 ref symlink to some other tree, if you have copied a whole
 archive by creating a symlink tree).
 
+Logging Updates
+---------------
+If config parameter "core.logAllRefUpdates" is true or the file
+"$GIT_DIR/logs/<ref>" exists then `git-update-ref` will append
+a line to the log file "$GIT_DIR/logs/<ref>" (dereferencing all
+symbolic refs before creating the log name) describing the change
+in ref value.  Log lines are formatted as:
+
+    . oldsha1 SP newsha1 SP committer LF
++
+Where "oldsha1" is the 40 character hexadecimal value previously
+stored in <ref>, "newsha1" is the 40 character hexadecimal value of
+<newvalue> and "committer" is the committer's name, email address
+and date in the standard GIT committer ident format.
+
+Optionally with -m:
+
+    . oldsha1 SP newsha1 SP committer TAB message LF
++
+Where all fields are as described above and "message" is the
+value supplied to the -m option.
+
+An update will fail (without changing <ref>) if the current user is
+unable to create a new log file, append to the existing log file
+or does not have committer information available.
+
 Author
 ------
 Written by Linus Torvalds <torvalds@osdl.org>.

Documentation/repository-layout.txt

@@ -128,3 +128,14 @@ remotes::
 	Stores shorthands to be used to give URL and default
 	refnames to interact with remote repository to `git
 	fetch`, `git pull` and `git push` commands.
+
+logs::
+	Records of changes made to refs are stored in this
+	directory.  See the documentation on git-update-ref
+	for more information.
+
+logs/refs/heads/`name`::
+	Records all changes made to the branch tip named `name`.
+
+logs/refs/tags/`name`::
+	Records all changes made to the tag named `name`.

cache.h

@@ -179,6 +179,7 @@ extern void rollback_index_file(struct cache_file *);
 extern int trust_executable_bit;
 extern int assume_unchanged;
 extern int prefer_symlink_refs;
+extern int log_all_ref_updates;
 extern int warn_ambiguous_refs;
 extern int diff_rename_limit_default;
 extern int shared_repository;

config.c

@@ -269,6 +269,11 @@ int git_default_config(const char *var, const char *value)
 		return 0;
 	}
 
+	if (!strcmp(var, "core.logallrefupdates")) {
+		log_all_ref_updates = git_config_bool(var, value);
+		return 0;
+	}
+
 	if (!strcmp(var, "core.warnambiguousrefs")) {
 		warn_ambiguous_refs = git_config_bool(var, value);
 		return 0;

environment.c

@@ -14,6 +14,7 @@ char git_default_name[MAX_GITNAME];
 int trust_executable_bit = 1;
 int assume_unchanged = 0;
 int prefer_symlink_refs = 0;
+int log_all_ref_updates = 0;
 int warn_ambiguous_refs = 1;
 int repository_format_version = 0;
 char git_commit_encoding[MAX_ENCODING_LENGTH] = "utf-8";

fetch.c

@@ -8,6 +8,7 @@
 #include "refs.h"
 
 const char *write_ref = NULL;
+const char *write_ref_log_details = NULL;
 
 int get_tree = 0;
 int get_history = 0;
@@ -202,23 +203,51 @@ static int mark_complete(const char *path, const unsigned char *sha1)
 
 int pull(char *target)
 {
+	struct ref_lock *lock = NULL;
 	unsigned char sha1[20];
+	char *msg;
+	int ret;
 
 	save_commit_buffer = 0;
 	track_object_refs = 0;
+	if (write_ref) {
+		lock = lock_ref_sha1(write_ref, NULL, 0);
+		if (!lock) {
+			error("Can't lock ref %s", write_ref);
+			return -1;
+		}
+	}
 
 	if (!get_recover)
 		for_each_ref(mark_complete);
 
-	if (interpret_target(target, sha1))
-		return error("Could not interpret %s as something to pull",
-			     target);
-	if (process(lookup_unknown_object(sha1)))
+	if (interpret_target(target, sha1)) {
+		error("Could not interpret %s as something to pull", target);
+		if (lock)
+			unlock_ref(lock);
 		return -1;
-	if (loop())
+	}
+	if (process(lookup_unknown_object(sha1))) {
+		if (lock)
+			unlock_ref(lock);
 		return -1;
-
-	if (write_ref)
-		write_ref_sha1_unlocked(write_ref, sha1);
+	}
+	if (loop()) {
+		if (lock)
+			unlock_ref(lock);
+		return -1;
+	}
+
+	if (write_ref) {
+		if (write_ref_log_details) {
+			msg = xmalloc(strlen(write_ref_log_details) + 12);
+			sprintf(msg, "fetch from %s", write_ref_log_details);
+		} else
+			msg = NULL;
+		ret = write_ref_sha1(lock, sha1, msg ? msg : "fetch (unknown)");
+		if (msg)
+			free(msg);
+		return ret;
+	}
 	return 0;
 }

fetch.h

@@ -25,6 +25,9 @@ extern int fetch_ref(char *ref, unsigned char *sha1);
 /* If set, the ref filename to write the target value to. */
 extern const char *write_ref;
 
+/* If set additional text will appear in the ref log. */
+extern const char *write_ref_log_details;
+
 /* Set to fetch the target tree. */
 extern int get_tree;
 

git-am.sh

@@ -413,7 +413,7 @@ do
 	parent=$(git-rev-parse --verify HEAD) &&
 	commit=$(git-commit-tree $tree -p $parent <"$dotest/final-commit") &&
 	echo Committed: $commit &&
-	git-update-ref HEAD $commit $parent ||
+	git-update-ref -m "am: $SUBJECT" HEAD $commit $parent ||
 	stop_here $this
 
 	if test -x "$GIT_DIR"/hooks/post-applypatch

git-applypatch.sh

@@ -204,7 +204,7 @@ echo Wrote tree $tree
 parent=$(git-rev-parse --verify HEAD) &&
 commit=$(git-commit-tree $tree -p $parent <"$final") || exit 1
 echo Committed: $commit
-git-update-ref HEAD $commit $parent || exit
+git-update-ref -m "applypatch: $SUBJECT" HEAD $commit $parent || exit
 
 if test -x "$GIT_DIR"/hooks/post-applypatch
 then

git-branch.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-USAGE='[(-d | -D) <branchname>] | [[-f] <branchname> [<start-point>]] | -r'
+USAGE='[-l] [(-d | -D) <branchname>] | [[-f] <branchname> [<start-point>]] | -r'
 LONG_USAGE='If no arguments, show available branches and mark current branch with a star.
 If one argument, create a new branch <branchname> based off of current HEAD.
 If two arguments, create a new branch <branchname> based off of <start-point>.'
@@ -42,6 +42,7 @@ If you are sure you want to delete it, run 'git branch -D $branch_name'."
 	    esac
 	    ;;
 	esac
+	rm -f "$GIT_DIR/logs/refs/heads/$branch_name"
 	rm -f "$GIT_DIR/refs/heads/$branch_name"
 	echo "Deleted branch $branch_name."
     done
@@ -55,6 +56,7 @@ ls_remote_branches () {
 }
 
 force=
+create_log=
 while case "$#,$1" in 0,*) break ;; *,-*) ;; *) break ;; esac
 do
 	case "$1" in
@@ -69,6 +71,9 @@ do
 	-f)
 		force="$1"
 		;;
+	-l)
+		create_log="yes"
+		;;
 	--)
 		shift
 		break
@@ -117,4 +122,9 @@ then
 		die "cannot force-update the current branch."
 	fi
 fi
-git update-ref "refs/heads/$branchname" $rev
+if test "$create_log" = 'yes'
+then
+	mkdir -p $(dirname "$GIT_DIR/logs/refs/heads/$branchname")
+	touch "$GIT_DIR/logs/refs/heads/$branchname"
+fi
+git update-ref -m "branch: Created from $head" "refs/heads/$branchname" $rev

git-checkout.sh

@@ -5,10 +5,13 @@ SUBDIRECTORY_OK=Sometimes
 . git-sh-setup
 
 old=$(git-rev-parse HEAD)
+old_name=HEAD
 new=
+new_name=
 force=
 branch=
 newbranch=
+newbranch_log=
 merge=
 while [ "$#" != "0" ]; do
     arg="$1"
@@ -24,6 +27,9 @@ while [ "$#" != "0" ]; do
 		git-check-ref-format "heads/$newbranch" ||
 			die "git checkout: we do not like '$newbranch' as a branch name."
 		;;
+	"-l")
+		newbranch_log=1
+		;;
 	"-f")
 		force=1
 		;;
@@ -44,16 +50,19 @@ while [ "$#" != "0" ]; do
 				exit 1
 			fi
 			new="$rev"
+			new_name="$arg^0"
 			if [ -f "$GIT_DIR/refs/heads/$arg" ]; then
 				branch="$arg"
 			fi
 		elif rev=$(git-rev-parse --verify "$arg^{tree}" 2>/dev/null)
 		then
 			# checking out selected paths from a tree-ish.
 			new="$rev"
+			new_name="$arg^{tree}"
 			branch=
 		else
 			new=
+			new_name=
 			branch=
 			set x "$arg" "$@"
 			shift
@@ -114,7 +123,7 @@ then
 	cd "$cdup"
 fi
 
-[ -z "$new" ] && new=$old
+[ -z "$new" ] && new=$old && new_name="$old_name"
 
 # If we don't have an old branch that we're switching to,
 # and we don't have a new branch name for the target we
@@ -187,9 +196,11 @@ fi
 #
 if [ "$?" -eq 0 ]; then
 	if [ "$newbranch" ]; then
-		leading=`expr "refs/heads/$newbranch" : '\(.*\)/'` &&
-		mkdir -p "$GIT_DIR/$leading" &&
-		echo $new >"$GIT_DIR/refs/heads/$newbranch" || exit
+		if [ "$newbranch_log" ]; then
+			mkdir -p $(dirname "$GIT_DIR/logs/refs/heads/$newbranch")
+			touch "$GIT_DIR/logs/refs/heads/$newbranch"
+		fi
+		git-update-ref -m "checkout: Created from $new_name" "refs/heads/$newbranch" $new || exit
 		branch="$newbranch"
 	fi
 	[ "$branch" ] &&

git-commit.sh

@@ -713,7 +713,8 @@ then
 		rm -f "$TMP_INDEX"
 	fi &&
 	commit=$(cat "$GIT_DIR"/COMMIT_MSG | git-commit-tree $tree $PARENTS) &&
-	git-update-ref HEAD $commit $current &&
+	rlogm=$(sed -e 1q "$GIT_DIR"/COMMIT_MSG) &&
+	git-update-ref -m "commit: $rlogm" HEAD $commit $current &&
 	rm -f -- "$GIT_DIR/MERGE_HEAD" &&
 	if test -f "$NEXT_INDEX"
 	then

git-reset.sh

@@ -48,7 +48,7 @@ then
 else
 	rm -f "$GIT_DIR/ORIG_HEAD"
 fi
-git-update-ref HEAD "$rev"
+git-update-ref -m "reset $reset_type $@" HEAD "$rev"
 
 case "$reset_type" in
 --hard )