Merge branch 'jn/update-contrib-example-merge'

* jn/update-contrib-example-merge: (24 commits)
  merge script: learn --[no-]rerere-autoupdate
  merge script: notice @{-1} shorthand
  merge script: handle --no-ff --no-commit correctly
  merge script: --ff-only to disallow true merge
  merge script: handle many-way octopus
  merge script: handle -m --log correctly
  merge script: forbid merge -s index
  merge script: allow custom strategies
  merge script: merge -X<option>
  merge script: improve log message subject
  merge script: refuse to merge during merge
  merge script: tweak unmerged files message to match builtin
  merge script: --squash, --ff from unborn branch are errors
  fmt-merge-msg -m to override merge title
  merge-base --independent to print reduced parent list in a merge
  merge-base --octopus to mimic show-branch --merge-base
  Documentation: add a SEE ALSO section for merge-base
  t6200 (fmt-merge-msg): style nitpicks
  t6010 (merge-base): modernize style
  t7600 (merge): test merge from branch yet to be born
  ...

9 files changed, 701 insertions, 562 deletions

diff --git a/Documentation/git-fmt-merge-msg.txt b/Documentation/git-fmt-merge-msg.txt
index a585dbe898..302f56b889 100644
--- a/Documentation/git-fmt-merge-msg.txt
+++ b/Documentation/git-fmt-merge-msg.txt
@@ -9,8 +9,8 @@ git-fmt-merge-msg - Produce a merge commit message
 SYNOPSIS
 --------
 [verse]
-'git fmt-merge-msg' [--log | --no-log] <$GIT_DIR/FETCH_HEAD
-'git fmt-merge-msg' [--log | --no-log] -F <file>
+'git fmt-merge-msg' [-m <message>] [--log | --no-log] <$GIT_DIR/FETCH_HEAD
+'git fmt-merge-msg' [-m <message>] [--log | --no-log] -F <file>
 
 DESCRIPTION
 -----------
@@ -38,6 +38,11 @@ OPTIONS
 	Synonyms to --log and --no-log; these are deprecated and will be
 	removed in the future.
 
+-m <message>::
+--message <message>::
+	Use <message> instead of the branch names for the first line
+	of the log message.  For use with `--log`.
+
 -F <file>::
 --file <file>::
 	Take the list of merged objects from <file> instead of
diff --git a/Documentation/git-merge-base.txt b/Documentation/git-merge-base.txt
index ce5b369985..eedef1bb1a 100644
--- a/Documentation/git-merge-base.txt
+++ b/Documentation/git-merge-base.txt
@@ -8,7 +8,9 @@ git-merge-base - Find as good common ancestors as possible for a merge
 
 SYNOPSIS
 --------
-'git merge-base' [-a|--all] <commit> <commit>...
+[verse]
+'git merge-base' [-a|--all] [--octopus] <commit> <commit>...
+'git merge-base' --independent <commit>...
 
 DESCRIPTION
 -----------
@@ -20,12 +22,12 @@ that does not have any better common ancestor is a 'best common
 ancestor', i.e. a 'merge base'.  Note that there can be more than one
 merge base for a pair of commits.
 
-Among the two commits to compute the merge base from, one is specified by
-the first commit argument on the command line; the other commit is a
-(possibly hypothetical) commit that is a merge across all the remaining
-commits on the command line.  As the most common special case, specifying only
-two commits on the command line means computing the merge base between
-the given two commits.
+Unless `--octopus` is given, among the two commits to compute the merge
+base from, one is specified by the first commit argument on the command
+line; the other commit is a (possibly hypothetical) commit that is a merge
+across all the remaining commits on the command line.  As the most common
+special case, specifying only two commits on the command line means
+computing the merge base between the given two commits.
 
 As a consequence, the 'merge base' is not necessarily contained in each of the
 commit arguments if more than two commits are specified. This is different
@@ -37,6 +39,18 @@ OPTIONS
 --all::
 	Output all merge bases for the commits, instead of just one.
 
+--octopus::
+	Compute the best common ancestors of all supplied commits,
+	in preparation for an n-way merge.  This mimics the behavior
+	of 'git show-branch --merge-base'.
+
+--independent::
+	Instead of printing merge bases, print a minimal subset of
+	the supplied commits with the same ancestors.  In other words,
+	among the commits given, list those which cannot be reached
+	from any other.  This mimics the behavior of 'git show-branch
+	--independent'.
+
 DISCUSSION
 ----------
 
@@ -96,6 +110,12 @@ Documentation
 --------------
 Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>.
 
+See also
+--------
+linkgit:git-rev-list[1],
+linkgit:git-show-branch[1],
+linkgit:git-merge[1]
+
 GIT
 ---
 Part of the linkgit:git[1] suite
diff --git a/builtin/fmt-merge-msg.c b/builtin/fmt-merge-msg.c
index a76cd4e9d1..e7e12eea25 100644
--- a/builtin/fmt-merge-msg.c
+++ b/builtin/fmt-merge-msg.c
@@ -7,7 +7,7 @@
 #include "string-list.h"
 
 static const char * const fmt_merge_msg_usage[] = {
-	"git fmt-merge-msg [--log|--no-log] [--file <file>]",
+	"git fmt-merge-msg [-m <message>] [--log|--no-log] [--file <file>]",
 	NULL
 };
 
@@ -319,11 +319,14 @@ int fmt_merge_msg_shortlog(struct strbuf *in, struct strbuf *out) {
 int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
 {
 	const char *inpath = NULL;
+	const char *message = NULL;
 	struct option options[] = {
 		OPT_BOOLEAN(0, "log",     &merge_summary, "populate log with the shortlog"),
 		{ OPTION_BOOLEAN, 0, "summary", &merge_summary, NULL,
 		  "alias for --log (deprecated)",
 		  PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
+		OPT_STRING('m', "message", &message, "text",
+			"use <text> as start of message"),
 		OPT_FILENAME('F', "file", &inpath, "file to read from"),
 		OPT_END()
 	};
@@ -337,6 +340,12 @@ int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
 			     0);
 	if (argc > 0)
 		usage_with_options(fmt_merge_msg_usage, options);
+	if (message && !merge_summary) {
+		char nl = '\n';
+		write_in_full(STDOUT_FILENO, message, strlen(message));
+		write_in_full(STDOUT_FILENO, &nl, 1);
+		return 0;
+	}
 
 	if (inpath && strcmp(inpath, "-")) {
 		in = fopen(inpath, "r");
@@ -346,7 +355,12 @@ int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
 
 	if (strbuf_read(&input, fileno(in), 0) < 0)
 		die_errno("could not read input file");
-	ret = fmt_merge_msg(merge_summary, &input, &output);
+	if (message) {
+		strbuf_addstr(&output, message);
+		ret = fmt_merge_msg_shortlog(&input, &output);
+	} else {
+		ret = fmt_merge_msg(merge_summary, &input, &output);
+	}
 	if (ret)
 		return ret;
 	write_in_full(STDOUT_FILENO, output.buf, output.len);
diff --git a/builtin/merge-base.c b/builtin/merge-base.c
index 54e7ec2237..96dd160731 100644
--- a/builtin/merge-base.c
+++ b/builtin/merge-base.c
@@ -23,7 +23,8 @@ static int show_merge_base(struct commit **rev, int rev_nr, int show_all)
 }
 
 static const char * const merge_base_usage[] = {
-	"git merge-base [-a|--all] <commit> <commit>...",
+	"git merge-base [-a|--all] [--octopus] <commit> <commit>...",
+	"git merge-base --independent <commit>...",
 	NULL
 };
 
@@ -41,21 +42,58 @@ static struct commit *get_commit_reference(const char *arg)
 	return r;
 }
 
+static int handle_octopus(int count, const char **args, int reduce, int show_all)
+{
+	struct commit_list *revs = NULL;
+	struct commit_list *result;
+	int i;
+
+	if (reduce)
+		show_all = 1;
+
+	for (i = count - 1; i >= 0; i--)
+		commit_list_insert(get_commit_reference(args[i]), &revs);
+
+	result = reduce ? reduce_heads(revs) : get_octopus_merge_bases(revs);
+
+	if (!result)
+		return 1;
+
+	while (result) {
+		printf("%s\n", sha1_to_hex(result->item->object.sha1));
+		if (!show_all)
+			return 0;
+		result = result->next;
+	}
+
+	return 0;
+}
+
 int cmd_merge_base(int argc, const char **argv, const char *prefix)
 {
 	struct commit **rev;
 	int rev_nr = 0;
 	int show_all = 0;
+	int octopus = 0;
+	int reduce = 0;
 
 	struct option options[] = {
-		OPT_BOOLEAN('a', "all", &show_all, "outputs all common ancestors"),
+		OPT_BOOLEAN('a', "all", &show_all, "output all common ancestors"),
+		OPT_BOOLEAN(0, "octopus", &octopus, "find ancestors for a single n-way merge"),
+		OPT_BOOLEAN(0, "independent", &reduce, "list revs not reachable from others"),
 		OPT_END()
 	};
 
 	git_config(git_default_config, NULL);
 	argc = parse_options(argc, argv, prefix, options, merge_base_usage, 0);
-	if (argc < 2)
+	if (!octopus && !reduce && argc < 2)
 		usage_with_options(merge_base_usage, options);
+	if (reduce && (show_all || octopus))
+		die("--independent cannot be used with other options");
+
+	if (octopus || reduce)
+		return handle_octopus(argc, argv, reduce, show_all);
+
 	rev = xmalloc(argc * sizeof(*rev));
 	while (argc-- > 0)
 		rev[rev_nr++] = get_commit_reference(*argv++);
diff --git a/builtin/merge.c b/builtin/merge.c
index da26cd629a..576e81f145 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -438,7 +438,7 @@ static void merge_name(const char *remote, struct strbuf *msg)
 		strbuf_addstr(&truname, "refs/heads/");
 		strbuf_addstr(&truname, remote);
 		strbuf_setlen(&truname, truname.len - len);
-		if (resolve_ref(truname.buf, buf_sha, 0, NULL)) {
+		if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
 			strbuf_addf(msg,
 				    "%s\t\tbranch '%s'%s of .\n",
 				    sha1_to_hex(remote_head->sha1),
diff --git a/contrib/examples/git-merge.sh b/contrib/examples/git-merge.sh
index 8f617fcb70..7b922c3948 100755
--- a/contrib/examples/git-merge.sh
+++ b/contrib/examples/git-merge.sh
@@ -15,7 +15,10 @@ log                  add list of one-line log to merge commit message
 squash               create a single commit instead of doing a merge
 commit               perform a commit if the merge succeeds (default)
 ff                   allow fast-forward (default)
+ff-only              abort if fast-forward is not possible
+rerere-autoupdate    update index with any reused conflict resolution
 s,strategy=          merge strategy to use
+X=                   option for selected merge strategy
 m,message=           message to be used for the merge commit (if any)
 "
 
@@ -25,26 +28,32 @@ require_work_tree
 cd_to_toplevel
 
 test -z "$(git ls-files -u)" ||
-	die "You are in the middle of a conflicted merge."
+	die "Merge is not possible because you have unmerged files."
+
+! test -e "$GIT_DIR/MERGE_HEAD" ||
+	die 'You have not concluded your merge (MERGE_HEAD exists).'
 
 LF='
 '
 
 all_strategies='recur recursive octopus resolve stupid ours subtree'
 all_strategies="$all_strategies recursive-ours recursive-theirs"
+not_strategies='base file index tree'
 default_twohead_strategies='recursive'
 default_octopus_strategies='octopus'
 no_fast_forward_strategies='subtree ours'
 no_trivial_strategies='recursive recur subtree ours recursive-ours recursive-theirs'
 use_strategies=
+xopt=
 
 allow_fast_forward=t
+fast_forward_only=
 allow_trivial_merge=t
-squash= no_commit= log_arg=
+squash= no_commit= log_arg= rr_arg=
 
 dropsave() {
 	rm -f -- "$GIT_DIR/MERGE_HEAD" "$GIT_DIR/MERGE_MSG" \
-		 "$GIT_DIR/MERGE_STASH" || exit 1
+		 "$GIT_DIR/MERGE_STASH" "$GIT_DIR/MERGE_MODE" || exit 1
 }
 
 savestate() {
@@ -131,21 +140,34 @@ finish () {
 merge_name () {
 	remote="$1"
 	rh=$(git rev-parse --verify "$remote^0" 2>/dev/null) || return
-	bh=$(git show-ref -s --verify "refs/heads/$remote" 2>/dev/null)
-	if test "$rh" = "$bh"
-	then
-		echo "$rh		branch '$remote' of ."
-	elif truname=$(expr "$remote" : '\(.*\)~[1-9][0-9]*$') &&
+	if truname=$(expr "$remote" : '\(.*\)~[0-9]*$') &&
 		git show-ref -q --verify "refs/heads/$truname" 2>/dev/null
 	then
 		echo "$rh		branch '$truname' (early part) of ."
-	elif test "$remote" = "FETCH_HEAD" -a -r "$GIT_DIR/FETCH_HEAD"
+		return
+	fi
+	if found_ref=$(git rev-parse --symbolic-full-name --verify \
+							"$remote" 2>/dev/null)
+	then
+		expanded=$(git check-ref-format --branch "$remote") ||
+			exit
+		if test "${found_ref#refs/heads/}" != "$found_ref"
+		then
+			echo "$rh		branch '$expanded' of ."
+			return
+		elif test "${found_ref#refs/remotes/}" != "$found_ref"
+		then
+			echo "$rh		remote branch '$expanded' of ."
+			return
+		fi
+	fi
+	if test "$remote" = "FETCH_HEAD" -a -r "$GIT_DIR/FETCH_HEAD"
 	then
 		sed -e 's/	not-for-merge	/		/' -e 1q \
 			"$GIT_DIR/FETCH_HEAD"
-	else
-		echo "$rh		commit '$remote'"
+		return
 	fi
+	echo "$rh		commit '$remote'"
 }
 
 parse_config () {
@@ -172,16 +194,36 @@ parse_config () {
 		--no-ff)
 			test "$squash" != t ||
 				die "You cannot combine --squash with --no-ff."
+			test "$fast_forward_only" != t ||
+				die "You cannot combine --ff-only with --no-ff."
 			allow_fast_forward=f ;;
+		--ff-only)
+			test "$allow_fast_forward" != f ||
+				die "You cannot combine --ff-only with --no-ff."
+			fast_forward_only=t ;;
+		--rerere-autoupdate|--no-rerere-autoupdate)
+			rr_arg=$1 ;;
 		-s|--strategy)
 			shift
 			case " $all_strategies " in
 			*" $1 "*)
-				use_strategies="$use_strategies$1 " ;;
+				use_strategies="$use_strategies$1 "
+				;;
 			*)
-				die "available strategies are: $all_strategies" ;;
+				case " $not_strategies " in
+				*" $1 "*)
+					false
+				esac &&
+				type "git-merge-$1" >/dev/null 2>&1 ||
+					die "available strategies are: $all_strategies"
+				use_strategies="$use_strategies$1 "
+				;;
 			esac
 			;;
+		-X)
+			shift
+			xopt="${xopt:+$xopt }$(git rev-parse --sq-quote "--$1")"
+			;;
 		-m|--message)
 			shift
 			merge_msg="$1"
@@ -245,6 +287,10 @@ then
 		exit 1
 	fi
 
+	test "$squash" != t ||
+		die "Squash commit into empty head not supported yet"
+	test "$allow_fast_forward" = t ||
+		die "Non-fast-forward into an empty head does not make sense"
 	rh=$(git rev-parse --verify "$1^0") ||
 		die "$1 - not something we can merge"
 
@@ -261,12 +307,18 @@ else
 	# the given message.  If remote is invalid we will die
 	# later in the common codepath so we discard the error
 	# in this loop.
-	merge_name=$(for remote
+	merge_msg="$(
+		for remote
 		do
 			merge_name "$remote"
-		done | git fmt-merge-msg $log_arg
-	)
-	merge_msg="${merge_msg:+$merge_msg$LF$LF}$merge_name"
+		done |
+		if test "$have_message" = t
+		then
+			git fmt-merge-msg -m "$merge_msg" $log_arg
+		else
+			git fmt-merge-msg $log_arg
+		fi
+	)"
 fi
 head=$(git rev-parse --verify "$head_arg"^0) || usage
 
@@ -335,7 +387,7 @@ case "$#" in
 	common=$(git merge-base --all $head "$@")
 	;;
 *)
-	common=$(git show-branch --merge-base $head "$@")
+	common=$(git merge-base --all --octopus $head "$@")
 	;;
 esac
 echo "$head" >"$GIT_DIR/ORIG_HEAD"
@@ -373,8 +425,8 @@ t,1,"$head",*)
 	# We are not doing octopus, not fast-forward, and have only
 	# one common.
 	git update-index --refresh 2>/dev/null
-	case "$allow_trivial_merge" in
-	t)
+	case "$allow_trivial_merge,$fast_forward_only" in
+	t,)
 		# See if it is really trivial.
 		git var GIT_COMMITTER_IDENT >/dev/null || exit
 		echo "Trying really trivial in-index merge..."
@@ -413,6 +465,11 @@ t,1,"$head",*)
 	;;
 esac
 
+if test "$fast_forward_only" = t
+then
+	die "Not possible to fast-forward, aborting."
+fi
+
 # We are going to make a new commit.
 git var GIT_COMMITTER_IDENT >/dev/null || exit
 
@@ -451,7 +508,7 @@ do
     # Remember which strategy left the state in the working tree
     wt_strategy=$strategy
 
-    git-merge-$strategy $common -- "$head_arg" "$@"
+    eval 'git-merge-$strategy '"$xopt"' $common -- "$head_arg" "$@"'
     exit=$?
     if test "$no_commit" = t && test "$exit" = 0
     then
@@ -489,9 +546,9 @@ if test '' != "$result_tree"
 then
     if test "$allow_fast_forward" = "t"
     then
-        parents=$(git show-branch --independent "$head" "$@")
+	parents=$(git merge-base --independent "$head" "$@")
     else
-        parents=$(git rev-parse "$head" "$@")
+	parents=$(git rev-parse "$head" "$@")
     fi
     parents=$(echo "$parents" | sed -e 's/^/-p /')
     result_commit=$(printf '%s\n' "$merge_msg" | git commit-tree $result_tree $parents) || exit
@@ -533,7 +590,15 @@ else
 	do
 		echo $remote
 	done >"$GIT_DIR/MERGE_HEAD"
-	printf '%s\n' "$merge_msg" >"$GIT_DIR/MERGE_MSG"
+	printf '%s\n' "$merge_msg" >"$GIT_DIR/MERGE_MSG" ||
+		die "Could not write to $GIT_DIR/MERGE_MSG"
+	if test "$allow_fast_forward" != t
+	then
+		printf "%s" no-ff
+	else
+		:
+	fi >"$GIT_DIR/MERGE_MODE" ||
+		die "Could not write to $GIT_DIR/MERGE_MODE"
 fi
 
 if test "$merge_was_ok" = t
@@ -550,6 +615,6 @@ Conflicts:
 		sed -e 's/^[^	]*	/	/' |
 		uniq
 	} >>"$GIT_DIR/MERGE_MSG"
-	git rerere
+	git rerere $rr_arg
 	die "Automatic merge failed; fix conflicts and then commit the result."
 fi
diff --git a/t/t6010-merge-base.sh b/t/t6010-merge-base.sh
index 0144d9e858..62197a3d35 100755
--- a/t/t6010-merge-base.sh
+++ b/t/t6010-merge-base.sh
@@ -3,175 +3,231 @@
 # Copyright (c) 2005 Junio C Hamano
 #
 
-test_description='Merge base computation.
+test_description='Merge base and parent list computation.
 '
 
 . ./test-lib.sh
 
-T=$(git write-tree)
-
-M=1130000000
-Z=+0000
-
-GIT_COMMITTER_EMAIL=git@comm.iter.xz
-GIT_COMMITTER_NAME='C O Mmiter'
-GIT_AUTHOR_NAME='A U Thor'
-GIT_AUTHOR_EMAIL=git@au.thor.xz
-export GIT_COMMITTER_EMAIL GIT_COMMITTER_NAME GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL
-
-doit() {
-	OFFSET=$1; shift
-	NAME=$1; shift
-	PARENTS=
-	for P
-	do
-		PARENTS="${PARENTS}-p $P "
-	done
-	GIT_COMMITTER_DATE="$(($M + $OFFSET)) $Z"
-	GIT_AUTHOR_DATE=$GIT_COMMITTER_DATE
-	export GIT_COMMITTER_DATE GIT_AUTHOR_DATE
-	commit=$(echo $NAME | git commit-tree $T $PARENTS)
-	echo $commit >.git/refs/tags/$NAME
-	echo $commit
-}
-
-#  E---D---C---B---A
-#  \'-_         \   \
-#   \  `---------G   \
-#    \                \
-#     F----------------H
-
-# Setup...
-E=$(doit 5 E)
-D=$(doit 4 D $E)
-F=$(doit 6 F $E)
-C=$(doit 3 C $D)
-B=$(doit 2 B $C)
-A=$(doit 1 A $B)
-G=$(doit 7 G $B $E)
-H=$(doit 8 H $A $F)
-
-test_expect_success 'compute merge-base (single)' \
-    'MB=$(git merge-base G H) &&
-     expr "$(git name-rev "$MB")" : "[0-9a-f]* tags/B"'
-
-test_expect_success 'compute merge-base (all)' \
-    'MB=$(git merge-base --all G H) &&
-     expr "$(git name-rev "$MB")" : "[0-9a-f]* tags/B"'
-
-test_expect_success 'compute merge-base with show-branch' \
-    'MB=$(git show-branch --merge-base G H) &&
-     expr "$(git name-rev "$MB")" : "[0-9a-f]* tags/B"'
-
-# Setup for second test to demonstrate that relying on timestamps in a
-# distributed SCM to provide a _consistent_ partial ordering of commits
-# leads to insanity.
-#
-#               Relative
-# Structure     timestamps
-#
-#   PL  PR        +4  +4
-#  /  \/  \      /  \/  \
-# L2  C2  R2    +3  -1  +3
-# |   |   |     |   |   |
-# L1  C1  R1    +2  -2  +2
-# |   |   |     |   |   |
-# L0  C0  R0    +1  -3  +1
-#   \ |  /        \ |  /
-#     S             0
-#
-# The left and right chains of commits can be of any length and complexity as
-# long as all of the timestamps are greater than that of S.
+test_expect_success 'setup' '
+	T=$(git write-tree) &&
 
-S=$(doit  0 S)
+	M=1130000000 &&
+	Z=+0000 &&
 
-C0=$(doit -3 C0 $S)
-C1=$(doit -2 C1 $C0)
-C2=$(doit -1 C2 $C1)
+	GIT_COMMITTER_EMAIL=git@comm.iter.xz &&
+	GIT_COMMITTER_NAME="C O Mmiter" &&
+	GIT_AUTHOR_NAME="A U Thor" &&
+	GIT_AUTHOR_EMAIL=git@au.thor.xz &&
+	export GIT_COMMITTER_EMAIL GIT_COMMITTER_NAME GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL &&
 
-L0=$(doit  1 L0 $S)
-L1=$(doit  2 L1 $L0)
-L2=$(doit  3 L2 $L1)
+	doit() {
+		OFFSET=$1 &&
+		NAME=$2 &&
+		shift 2 &&
 
-R0=$(doit  1 R0 $S)
-R1=$(doit  2 R1 $R0)
-R2=$(doit  3 R2 $R1)
+		PARENTS= &&
+		for P
+		do
+			PARENTS="${PARENTS}-p $P "
+		done &&
 
-PL=$(doit  4 PL $L2 $C2)
-PR=$(doit  4 PR $C2 $R2)
+		GIT_COMMITTER_DATE="$(($M + $OFFSET)) $Z" &&
+		GIT_AUTHOR_DATE=$GIT_COMMITTER_DATE &&
+		export GIT_COMMITTER_DATE GIT_AUTHOR_DATE &&
 
-test_expect_success 'compute merge-base (single)' \
-    'MB=$(git merge-base PL PR) &&
-     expr "$(git name-rev "$MB")" : "[0-9a-f]* tags/C2"'
+		commit=$(echo $NAME | git commit-tree $T $PARENTS) &&
 
-test_expect_success 'compute merge-base (all)' \
-    'MB=$(git merge-base --all PL PR) &&
-     expr "$(git name-rev "$MB")" : "[0-9a-f]* tags/C2"'
+		echo $commit >.git/refs/tags/$NAME &&
+		echo $commit
+	}
+'
 
-# Another set to demonstrate base between one commit and a merge
-# in the documentation.
-#
-# * C (MMC) * B (MMB) * A  (MMA)
-# * o       * o       * o
-# * o       * o       * o
-# * o       * o       * o
-# * o       | _______/
-# |         |/
-# |         * 1 (MM1)
-# | _______/
-# |/
-# * root (MMR)
+test_expect_success 'set up G and H' '
+	# E---D---C---B---A
+	# \"-_         \   \
+	#  \  `---------G   \
+	#   \                \
+	#    F----------------H
+	E=$(doit 5 E) &&
+	D=$(doit 4 D $E) &&
+	F=$(doit 6 F $E) &&
+	C=$(doit 3 C $D) &&
+	B=$(doit 2 B $C) &&
+	A=$(doit 1 A $B) &&
+	G=$(doit 7 G $B $E) &&
+	H=$(doit 8 H $A $F)
+'
+
+test_expect_success 'merge-base G H' '
+	git name-rev $B >expected &&
+
+	MB=$(git merge-base G H) &&
+	git name-rev "$MB" >actual.single &&
+
+	MB=$(git merge-base --all G H) &&
+	git name-rev "$MB" >actual.all &&
+
+	MB=$(git show-branch --merge-base G H) &&
+	git name-rev "$MB" >actual.sb &&
+
+	test_cmp expected actual.single &&
+	test_cmp expected actual.all &&
+	test_cmp expected actual.sb
+'
 
+test_expect_success 'merge-base/show-branch --independent' '
+	git name-rev "$H" >expected1 &&
+	git name-rev "$H" "$G" >expected2 &&
+
+	parents=$(git merge-base --independent H) &&
+	git name-rev $parents >actual1.mb &&
+	parents=$(git merge-base --independent A H G) &&
+	git name-rev $parents >actual2.mb &&
+
+	parents=$(git show-branch --independent H) &&
+	git name-rev $parents >actual1.sb &&
+	parents=$(git show-branch --independent A H G) &&
+	git name-rev $parents >actual2.sb &&
+
+	test_cmp expected1 actual1.mb &&
+	test_cmp expected2 actual2.mb &&
+	test_cmp expected1 actual1.sb &&
+	test_cmp expected2 actual2.sb
+'
+
+test_expect_success 'unsynchronized clocks' '
+	# This test is to demonstrate that relying on timestamps in a distributed
+	# SCM to provide a _consistent_ partial ordering of commits leads to
+	# insanity.
+	#
+	#               Relative
+	# Structure     timestamps
+	#
+	#   PL  PR        +4  +4
+	#  /  \/  \      /  \/  \
+	# L2  C2  R2    +3  -1  +3
+	# |   |   |     |   |   |
+	# L1  C1  R1    +2  -2  +2
+	# |   |   |     |   |   |
+	# L0  C0  R0    +1  -3  +1
+	#   \ |  /        \ |  /
+	#     S             0
+	#
+	# The left and right chains of commits can be of any length and complexity as
+	# long as all of the timestamps are greater than that of S.
+
+	S=$(doit  0 S) &&
+
+	C0=$(doit -3 C0 $S) &&
+	C1=$(doit -2 C1 $C0) &&
+	C2=$(doit -1 C2 $C1) &&
+
+	L0=$(doit  1 L0 $S) &&
+	L1=$(doit  2 L1 $L0) &&
+	L2=$(doit  3 L2 $L1) &&
+
+	R0=$(doit  1 R0 $S) &&
+	R1=$(doit  2 R1 $R0) &&
+	R2=$(doit  3 R2 $R1) &&
+
+	PL=$(doit  4 PL $L2 $C2) &&
+	PR=$(doit  4 PR $C2 $R2)
+
+	git name-rev $C2 >expected &&
+
+	MB=$(git merge-base PL PR) &&
+	git name-rev "$MB" >actual.single &&
+
+	MB=$(git merge-base --all PL PR) &&
+	git name-rev "$MB" >actual.all &&
+
+	test_cmp expected actual.single &&
+	test_cmp expected actual.all
+'
+
+test_expect_success '--independent with unsynchronized clocks' '
+	IB=$(doit 0 IB) &&
+	I1=$(doit -10 I1 $IB) &&
+	I2=$(doit  -9 I2 $I1) &&
+	I3=$(doit  -8 I3 $I2) &&
+	I4=$(doit  -7 I4 $I3) &&
+	I5=$(doit  -6 I5 $I4) &&
+	I6=$(doit  -5 I6 $I5) &&
+	I7=$(doit  -4 I7 $I6) &&
+	I8=$(doit  -3 I8 $I7) &&
+	IH=$(doit  -2 IH $I8) &&
+
+	echo $IH >expected &&
+	git merge-base --independent IB IH >actual &&
+	test_cmp expected actual
+'
 
 test_expect_success 'merge-base for octopus-step (setup)' '
-	test_tick && git commit --allow-empty -m root && git tag MMR &&
-	test_tick && git commit --allow-empty -m 1 && git tag MM1 &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m A && git tag MMA &&
+	# Another set to demonstrate base between one commit and a merge
+	# in the documentation.
+	#
+	# * C (MMC) * B (MMB) * A  (MMA)
+	# * o       * o       * o
+	# * o       * o       * o
+	# * o       * o       * o
+	# * o       | _______/
+	# |         |/
+	# |         * 1 (MM1)
+	# | _______/
+	# |/
+	# * root (MMR)
+
+	test_commit MMR &&
+	test_commit MM1 &&
+	test_commit MM-o &&
+	test_commit MM-p &&
+	test_commit MM-q &&
+	test_commit MMA &&
 	git checkout MM1 &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m B && git tag MMB &&
+	test_commit MM-r &&
+	test_commit MM-s &&
+	test_commit MM-t &&
+	test_commit MMB &&
 	git checkout MMR &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m C && git tag MMC
+	test_commit MM-u &&
+	test_commit MM-v &&
+	test_commit MM-w &&
+	test_commit MM-x &&
+	test_commit MMC
 '
 
 test_expect_success 'merge-base A B C' '
-	MB=$(git merge-base --all MMA MMB MMC) &&
-	MM1=$(git rev-parse --verify MM1) &&
-	test "$MM1" = "$MB"
-'
+	git rev-parse --verify MM1 >expected &&
+	git rev-parse --verify MMR >expected.sb &&
 
-test_expect_success 'merge-base A B C using show-branch' '
-	MB=$(git show-branch --merge-base MMA MMB MMC) &&
-	MMR=$(git rev-parse --verify MMR) &&
-	test "$MMR" = "$MB"
+	git merge-base --all MMA MMB MMC >actual &&
+	git merge-base --all --octopus MMA MMB MMC >actual.common &&
+	git show-branch --merge-base MMA MMB MMC >actual.sb &&
+
+	test_cmp expected actual &&
+	test_cmp expected.sb actual.common &&
+	test_cmp expected.sb actual.sb
 '
 
-test_expect_success 'criss-cross merge-base for octopus-step (setup)' '
+test_expect_success 'criss-cross merge-base for octopus-step' '
 	git reset --hard MMR &&
-	test_tick && git commit --allow-empty -m 1 && git tag CC1 &&
+	test_commit CC1 &&
 	git reset --hard E &&
-	test_tick && git commit --allow-empty -m 2 && git tag CC2 &&
-	test_tick && git merge -s ours CC1 &&
-	test_tick && git commit --allow-empty -m o &&
-	test_tick && git commit --allow-empty -m B && git tag CCB &&
+	test_commit CC2 &&
+	test_tick &&
+	git merge -s ours CC1 &&
+	test_commit CC-o &&
+	test_commit CCB &&
 	git reset --hard CC1 &&
-	test_tick && git merge -s ours CC2 &&
-	test_tick && git commit --allow-empty -m A && git tag CCA
-'
+	git merge -s ours CC2 &&
+	test_commit CCA &&
+
+	git rev-parse CC1 CC2 >expected &&
+	git merge-base --all CCB CCA^^ CCA^^2 >actual &&
 
-test_expect_success 'merge-base B A^^ A^^2' '
-	MB0=$(git merge-base --all CCB CCA^^ CCA^^2 | sort) &&
-	MB1=$(git rev-parse CC1 CC2 | sort) &&
-	test "$MB0" = "$MB1"
+	sort expected >expected.sorted &&
+	sort actual >actual.sorted &&
+	test_cmp expected.sorted actual.sorted
 '
 
 test_done
diff --git a/t/t6200-fmt-merge-msg.sh b/t/t6200-fmt-merge-msg.sh
index 42f8ece097..71f6cad3c2 100755
--- a/t/t6200-fmt-merge-msg.sh
+++ b/t/t6200-fmt-merge-msg.sh
@@ -70,14 +70,13 @@ test_expect_success setup '
 		i=$(($i+1))
 	done &&
 
-	git show-branch
-'
+	git show-branch &&
 
-cat >expected <<\EOF
-Merge branch 'left'
-EOF
+	apos="'\''"
+'
 
-test_expect_success 'merge-msg test #1' '
+test_expect_success 'message for merging local branch' '
+	echo "Merge branch ${apos}left${apos}" >expected &&
 
 	git checkout master &&
 	git fetch . left &&
@@ -86,11 +85,8 @@ test_expect_success 'merge-msg test #1' '
 	test_cmp expected actual
 '
 
-cat >expected <<EOF
-Merge branch 'left' of $(pwd)
-EOF
-
-test_expect_success 'merge-msg test #2' '
+test_expect_success 'message for merging external branch' '
+	echo "Merge branch ${apos}left${apos} of $(pwd)" >expected &&
 
 	git checkout master &&
 	git fetch "$(pwd)" left &&
@@ -99,139 +95,140 @@ test_expect_success 'merge-msg test #2' '
 	test_cmp expected actual
 '
 
-cat >expected <<\EOF
-Merge branch 'left'
-
-* left:
-  Left #5
-  Left #4
-  Left #3
-  Common #2
-  Common #1
-EOF
+test_expect_success '[merge] summary/log configuration' '
+	cat >expected <<-EOF &&
+	Merge branch ${apos}left${apos}
 
-test_expect_success 'merge-msg test #3-1' '
+	* left:
+	  Left #5
+	  Left #4
+	  Left #3
+	  Common #2
+	  Common #1
+	EOF
 
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
 	git config merge.log true &&
+	test_might_fail git config --unset-all merge.summary &&
 
 	git checkout master &&
 	test_tick &&
 	git fetch . left &&
 
-	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
-	test_cmp expected actual
-'
-
-test_expect_success 'merge-msg test #3-2' '
+	git fmt-merge-msg <.git/FETCH_HEAD >actual1 &&
 
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+	test_might_fail git config --unset-all merge.log &&
 	git config merge.summary true &&
 
 	git checkout master &&
 	test_tick &&
 	git fetch . left &&
 
-	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
-	test_cmp expected actual
-'
-
-cat >expected <<\EOF
-Merge branches 'left' and 'right'
+	git fmt-merge-msg <.git/FETCH_HEAD >actual2 &&
 
-* left:
-  Left #5
-  Left #4
-  Left #3
-  Common #2
-  Common #1
+	test_cmp expected actual1 &&
+	test_cmp expected actual2
+'
 
-* right:
-  Right #5
-  Right #4
-  Right #3
-  Common #2
-  Common #1
-EOF
+test_expect_success 'fmt-merge-msg -m' '
+	echo "Sync with left" >expected &&
+	cat >expected.log <<-EOF &&
+	Sync with left
+
+	* ${apos}left${apos} of $(pwd):
+	  Left #5
+	  Left #4
+	  Left #3
+	  Common #2
+	  Common #1
+	EOF
+
+	test_might_fail git config --unset merge.log &&
+	test_might_fail git config --unset merge.summary &&
+	git checkout master &&
+	git fetch "$(pwd)" left &&
+	git fmt-merge-msg -m "Sync with left" <.git/FETCH_HEAD >actual &&
+	git fmt-merge-msg --log -m "Sync with left" \
+					<.git/FETCH_HEAD >actual.log &&
+	git config merge.log true &&
+	git fmt-merge-msg -m "Sync with left" \
+					<.git/FETCH_HEAD >actual.log-config &&
+	git fmt-merge-msg --no-log -m "Sync with left" \
+					<.git/FETCH_HEAD >actual.nolog &&
+
+	test_cmp expected actual &&
+	test_cmp expected.log actual.log &&
+	test_cmp expected.log actual.log-config &&
+	test_cmp expected actual.nolog
+'
 
-test_expect_success 'merge-msg test #4-1' '
+test_expect_success 'setup: expected shortlog for two branches' '
+	cat >expected <<-EOF
+	Merge branches ${apos}left${apos} and ${apos}right${apos}
+
+	* left:
+	  Left #5
+	  Left #4
+	  Left #3
+	  Common #2
+	  Common #1
+
+	* right:
+	  Right #5
+	  Right #4
+	  Right #3
+	  Common #2
+	  Common #1
+	EOF
+'
 
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+test_expect_success 'shortlog for two branches' '
 	git config merge.log true &&
-
+	test_might_fail git config --unset-all merge.summary &&
 	git checkout master &&
 	test_tick &&
 	git fetch . left right &&
+	git fmt-merge-msg <.git/FETCH_HEAD >actual1 &&
 
-	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
-	test_cmp expected actual
-'
-
-test_expect_success 'merge-msg test #4-2' '
-
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+	test_might_fail git config --unset-all merge.log &&
 	git config merge.summary true &&
-
 	git checkout master &&
 	test_tick &&
 	git fetch . left right &&
+	git fmt-merge-msg <.git/FETCH_HEAD >actual2 &&
 
-	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
-	test_cmp expected actual
-'
-
-test_expect_success 'merge-msg test #5-1' '
-
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
 	git config merge.log yes &&
-
+	test_might_fail git config --unset-all merge.summary &&
 	git checkout master &&
 	test_tick &&
 	git fetch . left right &&
+	git fmt-merge-msg <.git/FETCH_HEAD >actual3 &&
 
-	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
-	test_cmp expected actual
-'
-
-test_expect_success 'merge-msg test #5-2' '
-
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+	test_might_fail git config --unset-all merge.log &&
 	git config merge.summary yes &&
-
 	git checkout master &&
 	test_tick &&
 	git fetch . left right &&
+	git fmt-merge-msg <.git/FETCH_HEAD >actual4 &&
 
-	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
-	test_cmp expected actual
+	test_cmp expected actual1 &&
+	test_cmp expected actual2 &&
+	test_cmp expected actual3 &&
+	test_cmp expected actual4
 '
 
 test_expect_success 'merge-msg -F' '
-
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+	test_might_fail git config --unset-all merge.log &&
 	git config merge.summary yes &&
-
 	git checkout master &&
 	test_tick &&
 	git fetch . left right &&
-
 	git fmt-merge-msg -F .git/FETCH_HEAD >actual &&
 	test_cmp expected actual
 '
 
 test_expect_success 'merge-msg -F in subdirectory' '
-
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+	test_might_fail git config --unset-all merge.log &&
 	git config merge.summary yes &&
-
 	git checkout master &&
 	test_tick &&
 	git fetch . left right &&
@@ -245,11 +242,11 @@ test_expect_success 'merge-msg -F in subdirectory' '
 '
 
 test_expect_success 'merge-msg with nothing to merge' '
-
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+	test_might_fail git config --unset-all merge.log &&
 	git config merge.summary yes &&
 
+	>empty &&
+
 	(
 		cd remote &&
 		git checkout -b unrelated &&
@@ -258,22 +255,20 @@ test_expect_success 'merge-msg with nothing to merge' '
 		git fmt-merge-msg <.git/FETCH_HEAD >../actual
 	) &&
 
-	test_cmp /dev/null actual
+	test_cmp empty actual
 '
 
-cat >expected <<\EOF
-Merge tag 'tag-r3'
-
-* tag 'tag-r3':
-  Right #3
-  Common #2
-  Common #1
-EOF
-
 test_expect_success 'merge-msg tag' '
+	cat >expected <<-EOF &&
+	Merge tag ${apos}tag-r3${apos}
 
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+	* tag ${apos}tag-r3${apos}:
+	  Right #3
+	  Common #2
+	  Common #1
+	EOF
+
+	test_might_fail git config --unset-all merge.log &&
 	git config merge.summary yes &&
 
 	git checkout master &&
@@ -284,26 +279,24 @@ test_expect_success 'merge-msg tag' '
 	test_cmp expected actual
 '
 
-cat >expected <<\EOF
-Merge tags 'tag-r3' and 'tag-l5'
-
-* tag 'tag-r3':
-  Right #3
-  Common #2
-  Common #1
-
-* tag 'tag-l5':
-  Left #5
-  Left #4
-  Left #3
-  Common #2
-  Common #1
-EOF
-
 test_expect_success 'merge-msg two tags' '
-
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+	cat >expected <<-EOF &&
+	Merge tags ${apos}tag-r3${apos} and ${apos}tag-l5${apos}
+
+	* tag ${apos}tag-r3${apos}:
+	  Right #3
+	  Common #2
+	  Common #1
+
+	* tag ${apos}tag-l5${apos}:
+	  Left #5
+	  Left #4
+	  Left #3
+	  Common #2
+	  Common #1
+	EOF
+
+	test_might_fail git config --unset-all merge.log &&
 	git config merge.summary yes &&
 
 	git checkout master &&
@@ -314,26 +307,24 @@ test_expect_success 'merge-msg two tags' '
 	test_cmp expected actual
 '
 
-cat >expected <<\EOF
-Merge branch 'left', tag 'tag-r3'
-
-* tag 'tag-r3':
-  Right #3
-  Common #2
-  Common #1
-
-* left:
-  Left #5
-  Left #4
-  Left #3
-  Common #2
-  Common #1
-EOF
-
 test_expect_success 'merge-msg tag and branch' '
-
-	git config --unset-all merge.log
-	git config --unset-all merge.summary
+	cat >expected <<-EOF &&
+	Merge branch ${apos}left${apos}, tag ${apos}tag-r3${apos}
+
+	* tag ${apos}tag-r3${apos}:
+	  Right #3
+	  Common #2
+	  Common #1
+
+	* left:
+	  Left #5
+	  Left #4
+	  Left #3
+	  Common #2
+	  Common #1
+	EOF
+
+	test_might_fail git config --unset-all merge.log &&
 	git config merge.summary yes &&
 
 	git checkout master &&
@@ -344,26 +335,27 @@ test_expect_success 'merge-msg tag and branch' '
 	test_cmp expected actual
 '
 
-cat >expected <<\EOF
-Merge branch 'long'
-
-* long: (35 commits)
-EOF
-
 test_expect_success 'merge-msg lots of commits' '
+	{
+		cat <<-EOF &&
+		Merge branch ${apos}long${apos}
+
+		* long: (35 commits)
+		EOF
+
+		i=29 &&
+		while test $i -gt 9
+		do
+			echo "  $i" &&
+			i=$(($i-1))
+		done &&
+		echo "  ..."
+	} >expected &&
 
 	git checkout master &&
 	test_tick &&
 	git fetch . long &&
 
-	i=29 &&
-	while test $i -gt 9
-	do
-		echo "  $i" &&
-		i=$(($i-1))
-	done >>expected &&
-	echo "  ..." >>expected
-
 	git fmt-merge-msg <.git/FETCH_HEAD >actual &&
 	test_cmp expected actual
 '
diff --git a/t/t7600-merge.sh b/t/t7600-merge.sh
index cde8390c1b..b4f40e4c3a 100755
--- a/t/t7600-merge.sh
+++ b/t/t7600-merge.sh
@@ -5,189 +5,103 @@
 
 test_description='git merge
 
-Testing basic merge operations/option parsing.'
+Testing basic merge operations/option parsing.
+
+! [c0] commit 0
+ ! [c1] commit 1
+  ! [c2] commit 2
+   ! [c3] commit 3
+    ! [c4] c4
+     ! [c5] c5
+      ! [c6] c6
+       * [master] Merge commit 'c1'
+--------
+       - [master] Merge commit 'c1'
+ +     * [c1] commit 1
+      +  [c6] c6
+     +   [c5] c5
+    ++   [c4] c4
+   ++++  [c3] commit 3
+  +      [c2] commit 2
++++++++* [c0] commit 0
+'
 
 . ./test-lib.sh
 
-cat >file <<EOF
-1
-2
-3
-4
-5
-6
-7
-8
-9
-EOF
-
-cat >file.1 <<EOF
-1 X
-2
-3
-4
-5
-6
-7
-8
-9
-EOF
-
-cat >file.5 <<EOF
-1
-2
-3
-4
-5 X
-6
-7
-8
-9
-EOF
-
-cat >file.9 <<EOF
-1
-2
-3
-4
-5
-6
-7
-8
-9 X
-EOF
-
-cat  >result.1 <<EOF
-1 X
-2
-3
-4
-5
-6
-7
-8
-9
-EOF
-
-cat >result.1-5 <<EOF
-1 X
-2
-3
-4
-5 X
-6
-7
-8
-9
-EOF
-
-cat >result.1-5-9 <<EOF
-1 X
-2
-3
-4
-5 X
-6
-7
-8
-9 X
-EOF
-
-create_merge_msgs() {
-	echo "Merge commit 'c2'" >msg.1-5 &&
-	echo "Merge commit 'c2'; commit 'c3'" >msg.1-5-9 &&
-	echo "Squashed commit of the following:" >squash.1 &&
-	echo >>squash.1 &&
-	git log --no-merges ^HEAD c1 >>squash.1 &&
-	echo "Squashed commit of the following:" >squash.1-5 &&
-	echo >>squash.1-5 &&
-	git log --no-merges ^HEAD c2 >>squash.1-5 &&
-	echo "Squashed commit of the following:" >squash.1-5-9 &&
-	echo >>squash.1-5-9 &&
-	git log --no-merges ^HEAD c2 c3 >>squash.1-5-9 &&
-	echo > msg.nolog &&
-	echo "* commit 'c3':" >msg.log &&
-	echo "  commit 3" >>msg.log &&
-	echo >>msg.log
-}
-
-verify_diff() {
-	if ! test_cmp "$1" "$2"
-	then
-		echo "$3"
-		false
-	fi
-}
-
-verify_merge() {
-	verify_diff "$2" "$1" "[OOPS] bad merge result" &&
-	if test $(git ls-files -u | wc -l) -gt 0
-	then
-		echo "[OOPS] unmerged files"
-		false
-	fi &&
-	if test_must_fail git diff --exit-code
-	then
-		echo "[OOPS] working tree != index"
-		false
-	fi &&
-	if test -n "$3"
-	then
-		git show -s --pretty=format:%s HEAD >msg.act &&
-		verify_diff "$3" msg.act "[OOPS] bad merge message"
-	fi
-}
-
-verify_head() {
-	if test "$1" != "$(git rev-parse HEAD)"
-	then
-		echo "[OOPS] HEAD != $1"
-		false
-	fi
-}
-
-verify_parents() {
-	i=1
-	while test $# -gt 0
-	do
-		if test "$1" != "$(git rev-parse HEAD^$i)"
+test_expect_success 'set up test data and helpers' '
+	printf "%s\n" 1 2 3 4 5 6 7 8 9 >file &&
+	printf "%s\n" "1 X" 2 3 4 5 6 7 8 9 >file.1 &&
+	printf "%s\n" 1 2 3 4 "5 X" 6 7 8 9 >file.5 &&
+	printf "%s\n" 1 2 3 4 5 6 7 8 "9 X" >file.9 &&
+	printf "%s\n" "1 X" 2 3 4 5 6 7 8 9 >result.1 &&
+	printf "%s\n" "1 X" 2 3 4 "5 X" 6 7 8 9 >result.1-5 &&
+	printf "%s\n" "1 X" 2 3 4 "5 X" 6 7 8 "9 X" >result.1-5-9 &&
+
+	create_merge_msgs() {
+		echo "Merge commit '\''c2'\''" >msg.1-5 &&
+		echo "Merge commit '\''c2'\''; commit '\''c3'\''" >msg.1-5-9 &&
+		{
+			echo "Squashed commit of the following:" &&
+			echo &&
+			git log --no-merges ^HEAD c1
+		} >squash.1 &&
+		{
+			echo "Squashed commit of the following:" &&
+			echo &&
+			git log --no-merges ^HEAD c2
+		} >squash.1-5 &&
+		{
+			echo "Squashed commit of the following:" &&
+			echo &&
+			git log --no-merges ^HEAD c2 c3
+		} >squash.1-5-9 &&
+		echo >msg.nolog &&
+		{
+			echo "* commit '\''c3'\'':" &&
+			echo "  commit 3" &&
+			echo
+		} >msg.log
+	} &&
+
+	verify_merge() {
+		test_cmp "$2" "$1" &&
+		git update-index --refresh &&
+		git diff --exit-code &&
+		if test -n "$3"
 		then
-			echo "[OOPS] HEAD^$i != $1"
-			return 1
+			git show -s --pretty=format:%s HEAD >msg.act &&
+			test_cmp "$3" msg.act
 		fi
-		i=$(expr $i + 1)
-		shift
-	done
-}
-
-verify_mergeheads() {
-	i=1
-	if ! test -f .git/MERGE_HEAD
-	then
-		echo "[OOPS] MERGE_HEAD is missing"
-		false
-	fi &&
-	while test $# -gt 0
-	do
-		head=$(head -n $i .git/MERGE_HEAD | sed -ne \$p)
-		if test "$1" != "$head"
-		then
-			echo "[OOPS] MERGE_HEAD $i != $1"
+	} &&
+
+	verify_head() {
+		echo "$1" >head.expected &&
+		git rev-parse HEAD >head.actual &&
+		test_cmp head.expected head.actual
+	} &&
+
+	verify_parents() {
+		printf "%s\n" "$@" >parents.expected &&
+		>parents.actual &&
+		i=1 &&
+		while test $i -le $#
+		do
+			git rev-parse HEAD^$i >>parents.actual &&
+			i=$(expr $i + 1) ||
 			return 1
-		fi
-		i=$(expr $i + 1)
-		shift
-	done
-}
+		done &&
+		test_cmp parents.expected parents.actual
+	} &&
 
-verify_no_mergehead() {
-	if test -f .git/MERGE_HEAD
-	then
-		echo "[OOPS] MERGE_HEAD exists"
-		false
-	fi
-}
+	verify_mergeheads() {
+		printf "%s\n" "$@" >mergehead.expected &&
+		test_cmp mergehead.expected .git/MERGE_HEAD
+	} &&
 
+	verify_no_mergehead() {
+		! test -e .git/MERGE_HEAD
+	}
+'
 
 test_expect_success 'setup' '
 	git add file &&
@@ -219,7 +133,7 @@ test_expect_success 'setup' '
 	create_merge_msgs
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'test option parsing' '
 	test_must_fail git merge -$ c1 &&
@@ -235,13 +149,19 @@ test_expect_success 'reject non-strategy with a git-merge-foo name' '
 '
 
 test_expect_success 'merge c0 with c1' '
+	echo "OBJID HEAD@{0}: merge c1: Fast-forward" >reflog.expected &&
+
 	git reset --hard c0 &&
 	git merge c1 &&
 	verify_merge file result.1 &&
-	verify_head "$c1"
+	verify_head "$c1" &&
+
+	git reflog -1 >reflog.actual &&
+	sed "s/$_x05[0-9a-f]*/OBJID/g" reflog.actual >reflog.fuzzy &&
+	test_cmp reflog.expected reflog.fuzzy
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c0 with c1 with --ff-only' '
 	git reset --hard c0 &&
@@ -251,7 +171,28 @@ test_expect_success 'merge c0 with c1 with --ff-only' '
 	verify_head "$c1"
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
+
+test_expect_success 'merge from unborn branch' '
+	git checkout -f master &&
+	test_might_fail git branch -D kid &&
+
+	echo "OBJID HEAD@{0}: initial pull" >reflog.expected &&
+
+	git checkout --orphan kid &&
+	test_when_finished "git checkout -f master" &&
+	git rm -fr . &&
+	test_tick &&
+	git merge --ff-only c1 &&
+	verify_merge file result.1 &&
+	verify_head "$c1" &&
+
+	git reflog -1 >reflog.actual &&
+	sed "s/$_x05[0-9a-f][0-9a-f]/OBJID/g" reflog.actual >reflog.fuzzy &&
+	test_cmp reflog.expected reflog.fuzzy
+'
+
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2' '
 	git reset --hard c1 &&
@@ -261,7 +202,7 @@ test_expect_success 'merge c1 with c2' '
 	verify_parents $c1 $c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2 and c3' '
 	git reset --hard c1 &&
@@ -271,7 +212,7 @@ test_expect_success 'merge c1 with c2 and c3' '
 	verify_parents $c1 $c2 $c3
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'failing merges with --ff-only' '
 	git reset --hard c1 &&
@@ -288,7 +229,7 @@ test_expect_success 'merge c0 with c1 (no-commit)' '
 	verify_head $c1
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2 (no-commit)' '
 	git reset --hard c1 &&
@@ -298,7 +239,7 @@ test_expect_success 'merge c1 with c2 (no-commit)' '
 	verify_mergeheads $c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2 and c3 (no-commit)' '
 	git reset --hard c1 &&
@@ -308,7 +249,7 @@ test_expect_success 'merge c1 with c2 and c3 (no-commit)' '
 	verify_mergeheads $c2 $c3
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c0 with c1 (squash)' '
 	git reset --hard c0 &&
@@ -316,10 +257,10 @@ test_expect_success 'merge c0 with c1 (squash)' '
 	verify_merge file result.1 &&
 	verify_head $c0 &&
 	verify_no_mergehead &&
-	verify_diff squash.1 .git/SQUASH_MSG "[OOPS] bad squash message"
+	test_cmp squash.1 .git/SQUASH_MSG
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c0 with c1 (squash, ff-only)' '
 	git reset --hard c0 &&
@@ -327,10 +268,10 @@ test_expect_success 'merge c0 with c1 (squash, ff-only)' '
 	verify_merge file result.1 &&
 	verify_head $c0 &&
 	verify_no_mergehead &&
-	verify_diff squash.1 .git/SQUASH_MSG "[OOPS] bad squash message"
+	test_cmp squash.1 .git/SQUASH_MSG
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2 (squash)' '
 	git reset --hard c1 &&
@@ -338,17 +279,17 @@ test_expect_success 'merge c1 with c2 (squash)' '
 	verify_merge file result.1-5 &&
 	verify_head $c1 &&
 	verify_no_mergehead &&
-	verify_diff squash.1-5 .git/SQUASH_MSG "[OOPS] bad squash message"
+	test_cmp squash.1-5 .git/SQUASH_MSG
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'unsuccesful merge of c1 with c2 (squash, ff-only)' '
 	git reset --hard c1 &&
 	test_must_fail git merge --squash --ff-only c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2 and c3 (squash)' '
 	git reset --hard c1 &&
@@ -356,10 +297,10 @@ test_expect_success 'merge c1 with c2 and c3 (squash)' '
 	verify_merge file result.1-5-9 &&
 	verify_head $c1 &&
 	verify_no_mergehead &&
-	verify_diff squash.1-5-9 .git/SQUASH_MSG "[OOPS] bad squash message"
+	test_cmp squash.1-5-9 .git/SQUASH_MSG
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2 (no-commit in config)' '
 	git reset --hard c1 &&
@@ -370,7 +311,7 @@ test_expect_success 'merge c1 with c2 (no-commit in config)' '
 	verify_mergeheads $c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2 (squash in config)' '
 	git reset --hard c1 &&
@@ -379,10 +320,10 @@ test_expect_success 'merge c1 with c2 (squash in config)' '
 	verify_merge file result.1-5 &&
 	verify_head $c1 &&
 	verify_no_mergehead &&
-	verify_diff squash.1-5 .git/SQUASH_MSG "[OOPS] bad squash message"
+	test_cmp squash.1-5 .git/SQUASH_MSG
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'override config option -n with --summary' '
 	git reset --hard c1 &&
@@ -412,7 +353,7 @@ test_expect_success 'override config option -n with --stat' '
 	fi
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'override config option --stat' '
 	git reset --hard c1 &&
@@ -428,7 +369,7 @@ test_expect_success 'override config option --stat' '
 	fi
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2 (override --no-commit)' '
 	git reset --hard c1 &&
@@ -439,7 +380,7 @@ test_expect_success 'merge c1 with c2 (override --no-commit)' '
 	verify_parents $c1 $c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c2 (override --squash)' '
 	git reset --hard c1 &&
@@ -450,7 +391,7 @@ test_expect_success 'merge c1 with c2 (override --squash)' '
 	verify_parents $c1 $c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c0 with c1 (no-ff)' '
 	git reset --hard c0 &&
@@ -461,7 +402,7 @@ test_expect_success 'merge c0 with c1 (no-ff)' '
 	verify_parents $c0 $c1
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'combining --squash and --no-ff is refused' '
 	test_must_fail git merge --squash --no-ff c1 &&
@@ -485,20 +426,20 @@ test_expect_success 'merge log message' '
 	git reset --hard c0 &&
 	git merge --no-log c2 &&
 	git show -s --pretty=format:%b HEAD >msg.act &&
-	verify_diff msg.nolog msg.act "[OOPS] bad merge log message" &&
+	test_cmp msg.nolog msg.act &&
 
 	git merge --log c3 &&
 	git show -s --pretty=format:%b HEAD >msg.act &&
-	verify_diff msg.log msg.act "[OOPS] bad merge log message" &&
+	test_cmp msg.log msg.act &&
 
 	git reset --hard HEAD^ &&
 	git config merge.log yes &&
 	git merge c3 &&
 	git show -s --pretty=format:%b HEAD >msg.act &&
-	verify_diff msg.log msg.act "[OOPS] bad merge log message"
+	test_cmp msg.log msg.act
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c0, c2, c0, and c1' '
        git reset --hard c1 &&
@@ -509,7 +450,7 @@ test_expect_success 'merge c1 with c0, c2, c0, and c1' '
        verify_parents $c1 $c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c0, c2, c0, and c1' '
        git reset --hard c1 &&
@@ -520,7 +461,7 @@ test_expect_success 'merge c1 with c0, c2, c0, and c1' '
        verify_parents $c1 $c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge c1 with c1 and c2' '
        git reset --hard c1 &&
@@ -531,7 +472,7 @@ test_expect_success 'merge c1 with c1 and c2' '
        verify_parents $c1 $c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge fast-forward in a dirty tree' '
        git reset --hard c0 &&
@@ -541,16 +482,16 @@ test_expect_success 'merge fast-forward in a dirty tree' '
        git merge c2
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'in-index merge' '
 	git reset --hard c0 &&
-	git merge --no-ff -s resolve c1 > out &&
+	git merge --no-ff -s resolve c1 >out &&
 	grep "Wonderful." out &&
 	verify_parents $c0 $c1
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'refresh the index before merging' '
 	git reset --hard c1 &&
@@ -558,31 +499,39 @@ test_expect_success 'refresh the index before merging' '
 	git merge c3
 '
 
-cat >expected <<EOF
-Merge branch 'c5' (early part)
+cat >expected.branch <<\EOF
+Merge branch 'c5-branch' (early part)
+EOF
+cat >expected.tag <<\EOF
+Merge commit 'c5~1'
 EOF
 
 test_expect_success 'merge early part of c2' '
 	git reset --hard c3 &&
-	echo c4 > c4.c &&
+	echo c4 >c4.c &&
 	git add c4.c &&
 	git commit -m c4 &&
 	git tag c4 &&
-	echo c5 > c5.c &&
+	echo c5 >c5.c &&
 	git add c5.c &&
 	git commit -m c5 &&
 	git tag c5 &&
 	git reset --hard c3 &&
-	echo c6 > c6.c &&
+	echo c6 >c6.c &&
 	git add c6.c &&
 	git commit -m c6 &&
 	git tag c6 &&
+	git branch -f c5-branch c5 &&
+	git merge c5-branch~1 &&
+	git show -s --pretty=format:%s HEAD >actual.branch &&
+	git reset --keep HEAD^ &&
 	git merge c5~1 &&
-	git show -s --pretty=format:%s HEAD > actual &&
-	test_cmp actual expected
+	git show -s --pretty=format:%s HEAD >actual.tag &&
+	test_cmp expected.branch actual.branch &&
+	test_cmp expected.tag actual.tag
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'merge --no-ff --no-commit && commit' '
 	git reset --hard c0 &&
@@ -591,13 +540,13 @@ test_expect_success 'merge --no-ff --no-commit && commit' '
 	verify_parents $c0 $c1
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_expect_success 'amending no-ff merge commit' '
 	EDITOR=: git commit --amend &&
 	verify_parents $c0 $c1
 '
 
-test_debug 'gitk --all'
+test_debug 'git log --graph --decorate --oneline --all'
 
 test_done