Merge branch 'jh/notes' (early part)

* 'jh/notes' (early part):
  Add selftests verifying concatenation of multiple notes for the same commit
  Refactor notes code to concatenate multiple notes annotating the same object
  Add selftests verifying that we can parse notes trees with various fanouts
  Teach the notes lookup code to parse notes trees with various fanout schemes
  Teach notes code to free its internal data structures on request
  Add '%N'-format for pretty-printing commit notes
  Add flags to get_commit_notes() to control the format of the note string
  t3302-notes-index-expensive: Speed up create_repo()
  fast-import: Add support for importing commit notes
  Teach "-m <msg>" and "-F <file>" to "git notes edit"
  Add an expensive test for git-notes
  Speed up git notes lookup
  Add a script to edit/inspect notes
  Introduce commit notes

Conflicts:
	.gitignore
	Documentation/pretty-formats.txt
	pretty.c

20 files changed, 1408 insertions, 10 deletions

diff --git a/.gitignore b/.gitignore
index f63992a6cc..ac02a580da 100644
--- a/.gitignore
+++ b/.gitignore
@@ -87,6 +87,7 @@
 /git-mktree
 /git-name-rev
 /git-mv
+/git-notes
 /git-pack-redundant
 /git-pack-objects
 /git-pack-refs
diff --git a/Documentation/config.txt b/Documentation/config.txt
index 1ff21938e7..78ee906319 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -456,6 +456,19 @@ On some file system/operating system combinations, this is unreliable.
 Set this config setting to 'rename' there; However, This will remove the
 check that makes sure that existing object files will not get overwritten.
 
+core.notesRef::
+	When showing commit messages, also show notes which are stored in
+	the given ref.  This ref is expected to contain files named
+	after the full SHA-1 of the commit they annotate.
++
+If such a file exists in the given ref, the referenced blob is read, and
+appended to the commit message, separated by a "Notes:" line.  If the
+given ref itself does not exist, it is not an error, but means that no
+notes should be printed.
++
+This setting defaults to "refs/notes/commits", and can be overridden by
+the `GIT_NOTES_REF` environment variable.
+
 add.ignore-errors::
 	Tells 'git-add' to continue adding files when some files cannot be
 	added due to indexing errors. Equivalent to the '--ignore-errors'
diff --git a/Documentation/git-fast-import.txt b/Documentation/git-fast-import.txt
index c2f483a8d2..288032c7b8 100644
--- a/Documentation/git-fast-import.txt
+++ b/Documentation/git-fast-import.txt
@@ -316,7 +316,7 @@ change to the project.
 	data
 	('from' SP <committish> LF)?
 	('merge' SP <committish> LF)?
-	(filemodify | filedelete | filecopy | filerename | filedeleteall)*
+	(filemodify | filedelete | filecopy | filerename | filedeleteall | notemodify)*
 	LF?
 ....
 
@@ -339,14 +339,13 @@ commit message use a 0 length data.  Commit messages are free-form
 and are not interpreted by Git.  Currently they must be encoded in
 UTF-8, as fast-import does not permit other encodings to be specified.
 
-Zero or more `filemodify`, `filedelete`, `filecopy`, `filerename`
-and `filedeleteall` commands
+Zero or more `filemodify`, `filedelete`, `filecopy`, `filerename`,
+`filedeleteall` and `notemodify` commands
 may be included to update the contents of the branch prior to
 creating the commit.  These commands may be supplied in any order.
 However it is recommended that a `filedeleteall` command precede
-all `filemodify`, `filecopy` and `filerename` commands in the same
-commit, as `filedeleteall`
-wipes the branch clean (see below).
+all `filemodify`, `filecopy`, `filerename` and `notemodify` commands in
+the same commit, as `filedeleteall` wipes the branch clean (see below).
 
 The `LF` after the command is optional (it used to be required).
 
@@ -595,6 +594,40 @@ more memory per active branch (less than 1 MiB for even most large
 projects); so frontends that can easily obtain only the affected
 paths for a commit are encouraged to do so.
 
+`notemodify`
+^^^^^^^^^^^^
+Included in a `commit` command to add a new note (annotating a given
+commit) or change the content of an existing note.  This command has
+two different means of specifying the content of the note.
+
+External data format::
+	The data content for the note was already supplied by a prior
+	`blob` command.  The frontend just needs to connect it to the
+	commit that is to be annotated.
++
+....
+	'N' SP <dataref> SP <committish> LF
+....
++
+Here `<dataref>` can be either a mark reference (`:<idnum>`)
+set by a prior `blob` command, or a full 40-byte SHA-1 of an
+existing Git blob object.
+
+Inline data format::
+	The data content for the note has not been supplied yet.
+	The frontend wants to supply it as part of this modify
+	command.
++
+....
+	'N' SP 'inline' SP <committish> LF
+	data
+....
++
+See below for a detailed description of the `data` command.
+
+In both formats `<committish>` is any of the commit specification
+expressions also accepted by `from` (see above).
+
 `mark`
 ~~~~~~
 Arranges for fast-import to save a reference to the current object, allowing
diff --git a/Documentation/git-notes.txt b/Documentation/git-notes.txt
new file mode 100644
index 0000000000..94cceb1319
--- /dev/null
+++ b/Documentation/git-notes.txt
@@ -0,0 +1,60 @@
+git-notes(1)
+============
+
+NAME
+----
+git-notes - Add/inspect commit notes
+
+SYNOPSIS
+--------
+[verse]
+'git-notes' (edit [-F <file> | -m <msg>] | show) [commit]
+
+DESCRIPTION
+-----------
+This command allows you to add notes to commit messages, without
+changing the commit.  To discern these notes from the message stored
+in the commit object, the notes are indented like the message, after
+an unindented line saying "Notes:".
+
+To disable commit notes, you have to set the config variable
+core.notesRef to the empty string.  Alternatively, you can set it
+to a different ref, something like "refs/notes/bugzilla".  This setting
+can be overridden by the environment variable "GIT_NOTES_REF".
+
+
+SUBCOMMANDS
+-----------
+
+edit::
+	Edit the notes for a given commit (defaults to HEAD).
+
+show::
+	Show the notes for a given commit (defaults to HEAD).
+
+
+OPTIONS
+-------
+-m <msg>::
+	Use the given note message (instead of prompting).
+	If multiple `-m` (or `-F`) options are given, their
+	values are concatenated as separate paragraphs.
+
+-F <file>::
+	Take the note message from the given file.  Use '-' to
+	read the note message from the standard input.
+	If multiple `-F` (or `-m`) options are given, their
+	values are concatenated as separate paragraphs.
+
+
+Author
+------
+Written by Johannes Schindelin <johannes.schindelin@gmx.de>
+
+Documentation
+-------------
+Documentation by Johannes Schindelin
+
+GIT
+---
+Part of the linkgit:git[7] suite
diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 38b9904791..09462021ea 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -123,6 +123,7 @@ The placeholders are:
 - '%s': subject
 - '%f': sanitized subject line, suitable for a filename
 - '%b': body
+- '%N': commit notes
 - '%gD': reflog selector, e.g., `refs/stash@\{1\}`
 - '%gd': shortened reflog selector, e.g., `stash@\{1\}`
 - '%gs': reflog subject
diff --git a/Makefile b/Makefile
index da418c39c9..abb7a741ee 100644
--- a/Makefile
+++ b/Makefile
@@ -343,6 +343,7 @@ SCRIPT_SH += git-merge-one-file.sh
 SCRIPT_SH += git-merge-resolve.sh
 SCRIPT_SH += git-mergetool.sh
 SCRIPT_SH += git-mergetool--lib.sh
+SCRIPT_SH += git-notes.sh
 SCRIPT_SH += git-parse-remote.sh
 SCRIPT_SH += git-pull.sh
 SCRIPT_SH += git-quiltimport.sh
@@ -457,6 +458,7 @@ LIB_H += ll-merge.h
 LIB_H += log-tree.h
 LIB_H += mailmap.h
 LIB_H += merge-recursive.h
+LIB_H += notes.h
 LIB_H += object.h
 LIB_H += pack.h
 LIB_H += pack-refs.h
@@ -542,6 +544,7 @@ LIB_OBJS += match-trees.o
 LIB_OBJS += merge-file.o
 LIB_OBJS += merge-recursive.o
 LIB_OBJS += name-hash.o
+LIB_OBJS += notes.o
 LIB_OBJS += object.o
 LIB_OBJS += pack-check.o
 LIB_OBJS += pack-refs.o
diff --git a/cache.h b/cache.h
index 2cfce27abd..f7533ff862 100644
--- a/cache.h
+++ b/cache.h
@@ -372,6 +372,8 @@ static inline enum object_type object_type(unsigned int mode)
 #define GITATTRIBUTES_FILE ".gitattributes"
 #define INFOATTRIBUTES_FILE "info/attributes"
 #define ATTRIBUTE_MACRO_PREFIX "[attr]"
+#define GIT_NOTES_REF_ENVIRONMENT "GIT_NOTES_REF"
+#define GIT_NOTES_DEFAULT_REF "refs/notes/commits"
 
 extern int is_bare_repository_cfg;
 extern int is_bare_repository(void);
@@ -568,6 +570,8 @@ enum object_creation_mode {
 
 extern enum object_creation_mode object_creation_mode;
 
+extern char *notes_ref_name;
+
 extern int grafts_replace_parents;
 
 #define GIT_REPO_VERSION 0
diff --git a/command-list.txt b/command-list.txt
index 59b0adc39b..cc5d48b385 100644
--- a/command-list.txt
+++ b/command-list.txt
@@ -74,6 +74,7 @@ git-mktag                               plumbingmanipulators
 git-mktree                              plumbingmanipulators
 git-mv                                  mainporcelain common
 git-name-rev                            plumbinginterrogators
+git-notes                               mainporcelain
 git-pack-objects                        plumbingmanipulators
 git-pack-redundant                      plumbinginterrogators
 git-pack-refs                           ancillarymanipulators
diff --git a/commit.c b/commit.c
index 51839fbedb..632061c2c3 100644
--- a/commit.c
+++ b/commit.c
@@ -5,6 +5,7 @@
 #include "utf8.h"
 #include "diff.h"
 #include "revision.h"
+#include "notes.h"
 
 int save_commit_buffer = 1;
 
diff --git a/config.c b/config.c
index c644061136..51f22088e7 100644
--- a/config.c
+++ b/config.c
@@ -467,6 +467,11 @@ static int git_default_core_config(const char *var, const char *value)
 		return 0;
 	}
 
+	if (!strcmp(var, "core.notesref")) {
+		notes_ref_name = xstrdup(value);
+		return 0;
+	}
+
 	if (!strcmp(var, "core.pager"))
 		return git_config_string(&pager_program, var, value);
 
diff --git a/environment.c b/environment.c
index 5de6837840..571ab56b7e 100644
--- a/environment.c
+++ b/environment.c
@@ -49,6 +49,7 @@ enum push_default_type push_default = PUSH_DEFAULT_MATCHING;
 #define OBJECT_CREATION_MODE OBJECT_CREATION_USES_HARDLINKS
 #endif
 enum object_creation_mode object_creation_mode = OBJECT_CREATION_MODE;
+char *notes_ref_name;
 int grafts_replace_parents = 1;
 
 /* Parallel index stat data preload? */
diff --git a/fast-import.c b/fast-import.c
index f4f1de6dd7..dd3c99d60d 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -22,8 +22,8 @@ Format of STDIN stream:
     ('author' sp name sp '<' email '>' sp when lf)?
     'committer' sp name sp '<' email '>' sp when lf
     commit_msg
-    ('from' sp (ref_str | hexsha1 | sha1exp_str | idnum) lf)?
-    ('merge' sp (ref_str | hexsha1 | sha1exp_str | idnum) lf)*
+    ('from' sp committish lf)?
+    ('merge' sp committish lf)*
     file_change*
     lf?;
   commit_msg ::= data;
@@ -41,15 +41,18 @@ Format of STDIN stream:
   file_obm ::= 'M' sp mode sp (hexsha1 | idnum) sp path_str lf;
   file_inm ::= 'M' sp mode sp 'inline' sp path_str lf
     data;
+  note_obm ::= 'N' sp (hexsha1 | idnum) sp committish lf;
+  note_inm ::= 'N' sp 'inline' sp committish lf
+    data;
 
   new_tag ::= 'tag' sp tag_str lf
-    'from' sp (ref_str | hexsha1 | sha1exp_str | idnum) lf
+    'from' sp committish lf
     ('tagger' sp name sp '<' email '>' sp when lf)?
     tag_msg;
   tag_msg ::= data;
 
   reset_branch ::= 'reset' sp ref_str lf
-    ('from' sp (ref_str | hexsha1 | sha1exp_str | idnum) lf)?
+    ('from' sp committish lf)?
     lf?;
 
   checkpoint ::= 'checkpoint' lf
@@ -88,6 +91,7 @@ Format of STDIN stream:
      # stream formatting is: \, " and LF.  Otherwise these values
      # are UTF8.
      #
+  committish  ::= (ref_str | hexsha1 | sha1exp_str | idnum);
   ref_str     ::= ref;
   sha1exp_str ::= sha1exp;
   tag_str     ::= tag;
@@ -2006,6 +2010,80 @@ static void file_change_cr(struct branch *b, int rename)
 		leaf.tree);
 }
 
+static void note_change_n(struct branch *b)
+{
+	const char *p = command_buf.buf + 2;
+	static struct strbuf uq = STRBUF_INIT;
+	struct object_entry *oe = oe;
+	struct branch *s;
+	unsigned char sha1[20], commit_sha1[20];
+	uint16_t inline_data = 0;
+
+	/* <dataref> or 'inline' */
+	if (*p == ':') {
+		char *x;
+		oe = find_mark(strtoumax(p + 1, &x, 10));
+		hashcpy(sha1, oe->sha1);
+		p = x;
+	} else if (!prefixcmp(p, "inline")) {
+		inline_data = 1;
+		p += 6;
+	} else {
+		if (get_sha1_hex(p, sha1))
+			die("Invalid SHA1: %s", command_buf.buf);
+		oe = find_object(sha1);
+		p += 40;
+	}
+	if (*p++ != ' ')
+		die("Missing space after SHA1: %s", command_buf.buf);
+
+	/* <committish> */
+	s = lookup_branch(p);
+	if (s) {
+		hashcpy(commit_sha1, s->sha1);
+	} else if (*p == ':') {
+		uintmax_t commit_mark = strtoumax(p + 1, NULL, 10);
+		struct object_entry *commit_oe = find_mark(commit_mark);
+		if (commit_oe->type != OBJ_COMMIT)
+			die("Mark :%" PRIuMAX " not a commit", commit_mark);
+		hashcpy(commit_sha1, commit_oe->sha1);
+	} else if (!get_sha1(p, commit_sha1)) {
+		unsigned long size;
+		char *buf = read_object_with_reference(commit_sha1,
+			commit_type, &size, commit_sha1);
+		if (!buf || size < 46)
+			die("Not a valid commit: %s", p);
+		free(buf);
+	} else
+		die("Invalid ref name or SHA1 expression: %s", p);
+
+	if (inline_data) {
+		static struct strbuf buf = STRBUF_INIT;
+
+		if (p != uq.buf) {
+			strbuf_addstr(&uq, p);
+			p = uq.buf;
+		}
+		read_next_command();
+		parse_data(&buf);
+		store_object(OBJ_BLOB, &buf, &last_blob, sha1, 0);
+	} else if (oe) {
+		if (oe->type != OBJ_BLOB)
+			die("Not a blob (actually a %s): %s",
+				typename(oe->type), command_buf.buf);
+	} else {
+		enum object_type type = sha1_object_info(sha1, NULL);
+		if (type < 0)
+			die("Blob not found: %s", command_buf.buf);
+		if (type != OBJ_BLOB)
+			die("Not a blob (actually a %s): %s",
+			    typename(type), command_buf.buf);
+	}
+
+	tree_content_set(&b->branch_tree, sha1_to_hex(commit_sha1), sha1,
+		S_IFREG | 0644, NULL);
+}
+
 static void file_change_deleteall(struct branch *b)
 {
 	release_tree_content_recursive(b->branch_tree.tree);
@@ -2175,6 +2253,8 @@ static void parse_new_commit(void)
 			file_change_cr(b, 1);
 		else if (!prefixcmp(command_buf.buf, "C "))
 			file_change_cr(b, 0);
+		else if (!prefixcmp(command_buf.buf, "N "))
+			note_change_n(b);
 		else if (!strcmp("deleteall", command_buf.buf))
 			file_change_deleteall(b);
 		else {
diff --git a/git-notes.sh b/git-notes.sh
new file mode 100755
index 0000000000..e642e47d9f
--- /dev/null
+++ b/git-notes.sh
@@ -0,0 +1,121 @@
+#!/bin/sh
+
+USAGE="(edit [-F <file> | -m <msg>] | show) [commit]"
+. git-sh-setup
+
+test -z "$1" && usage
+ACTION="$1"; shift
+
+test -z "$GIT_NOTES_REF" && GIT_NOTES_REF="$(git config core.notesref)"
+test -z "$GIT_NOTES_REF" && GIT_NOTES_REF="refs/notes/commits"
+
+MESSAGE=
+while test $# != 0
+do
+	case "$1" in
+	-m)
+		test "$ACTION" = "edit" || usage
+		shift
+		if test "$#" = "0"; then
+			die "error: option -m needs an argument"
+		else
+			if [ -z "$MESSAGE" ]; then
+				MESSAGE="$1"
+			else
+				MESSAGE="$MESSAGE
+
+$1"
+			fi
+			shift
+		fi
+		;;
+	-F)
+		test "$ACTION" = "edit" || usage
+		shift
+		if test "$#" = "0"; then
+			die "error: option -F needs an argument"
+		else
+			if [ -z "$MESSAGE" ]; then
+				MESSAGE="$(cat "$1")"
+			else
+				MESSAGE="$MESSAGE
+
+$(cat "$1")"
+			fi
+			shift
+		fi
+		;;
+	-*)
+		usage
+		;;
+	*)
+		break
+		;;
+	esac
+done
+
+COMMIT=$(git rev-parse --verify --default HEAD "$@") ||
+die "Invalid commit: $@"
+
+case "$ACTION" in
+edit)
+	if [ "${GIT_NOTES_REF#refs/notes/}" = "$GIT_NOTES_REF" ]; then
+		die "Refusing to edit notes in $GIT_NOTES_REF (outside of refs/notes/)"
+	fi
+
+	MSG_FILE="$GIT_DIR/new-notes-$COMMIT"
+	GIT_INDEX_FILE="$MSG_FILE.idx"
+	export GIT_INDEX_FILE
+
+	trap '
+		test -f "$MSG_FILE" && rm "$MSG_FILE"
+		test -f "$GIT_INDEX_FILE" && rm "$GIT_INDEX_FILE"
+	' 0
+
+	CURRENT_HEAD=$(git show-ref "$GIT_NOTES_REF" | cut -f 1 -d ' ')
+	if [ -z "$CURRENT_HEAD" ]; then
+		PARENT=
+	else
+		PARENT="-p $CURRENT_HEAD"
+		git read-tree "$GIT_NOTES_REF" || die "Could not read index"
+	fi
+
+	if [ -z "$MESSAGE" ]; then
+		GIT_NOTES_REF= git log -1 $COMMIT | sed "s/^/#/" > "$MSG_FILE"
+		if [ ! -z "$CURRENT_HEAD" ]; then
+			git cat-file blob :$COMMIT >> "$MSG_FILE" 2> /dev/null
+		fi
+		core_editor="$(git config core.editor)"
+		${GIT_EDITOR:-${core_editor:-${VISUAL:-${EDITOR:-vi}}}} "$MSG_FILE"
+	else
+		echo "$MESSAGE" > "$MSG_FILE"
+	fi
+
+	grep -v ^# < "$MSG_FILE" | git stripspace > "$MSG_FILE".processed
+	mv "$MSG_FILE".processed "$MSG_FILE"
+	if [ -s "$MSG_FILE" ]; then
+		BLOB=$(git hash-object -w "$MSG_FILE") ||
+			die "Could not write into object database"
+		git update-index --add --cacheinfo 0644 $BLOB $COMMIT ||
+			die "Could not write index"
+	else
+		test -z "$CURRENT_HEAD" &&
+			die "Will not initialise with empty tree"
+		git update-index --force-remove $COMMIT ||
+			die "Could not update index"
+	fi
+
+	TREE=$(git write-tree) || die "Could not write tree"
+	NEW_HEAD=$(echo Annotate $COMMIT | git commit-tree $TREE $PARENT) ||
+		die "Could not annotate"
+	git update-ref -m "Annotate $COMMIT" \
+		"$GIT_NOTES_REF" $NEW_HEAD $CURRENT_HEAD
+;;
+show)
+	git rev-parse -q --verify "$GIT_NOTES_REF":$COMMIT > /dev/null ||
+		die "No note for commit $COMMIT."
+	git show "$GIT_NOTES_REF":$COMMIT
+;;
+*)
+	usage
+esac
diff --git a/notes.c b/notes.c
new file mode 100644
index 0000000000..50a4672d7c
--- /dev/null
+++ b/notes.c
@@ -0,0 +1,429 @@
+#include "cache.h"
+#include "commit.h"
+#include "notes.h"
+#include "refs.h"
+#include "utf8.h"
+#include "strbuf.h"
+#include "tree-walk.h"
+
+/*
+ * Use a non-balancing simple 16-tree structure with struct int_node as
+ * internal nodes, and struct leaf_node as leaf nodes. Each int_node has a
+ * 16-array of pointers to its children.
+ * The bottom 2 bits of each pointer is used to identify the pointer type
+ * - ptr & 3 == 0 - NULL pointer, assert(ptr == NULL)
+ * - ptr & 3 == 1 - pointer to next internal node - cast to struct int_node *
+ * - ptr & 3 == 2 - pointer to note entry - cast to struct leaf_node *
+ * - ptr & 3 == 3 - pointer to subtree entry - cast to struct leaf_node *
+ *
+ * The root node is a statically allocated struct int_node.
+ */
+struct int_node {
+	void *a[16];
+};
+
+/*
+ * Leaf nodes come in two variants, note entries and subtree entries,
+ * distinguished by the LSb of the leaf node pointer (see above).
+ * As a note entry, the key is the SHA1 of the referenced commit, and the
+ * value is the SHA1 of the note object.
+ * As a subtree entry, the key is the prefix SHA1 (w/trailing NULs) of the
+ * referenced commit, using the last byte of the key to store the length of
+ * the prefix. The value is the SHA1 of the tree object containing the notes
+ * subtree.
+ */
+struct leaf_node {
+	unsigned char key_sha1[20];
+	unsigned char val_sha1[20];
+};
+
+#define PTR_TYPE_NULL     0
+#define PTR_TYPE_INTERNAL 1
+#define PTR_TYPE_NOTE     2
+#define PTR_TYPE_SUBTREE  3
+
+#define GET_PTR_TYPE(ptr)       ((uintptr_t) (ptr) & 3)
+#define CLR_PTR_TYPE(ptr)       ((void *) ((uintptr_t) (ptr) & ~3))
+#define SET_PTR_TYPE(ptr, type) ((void *) ((uintptr_t) (ptr) | (type)))
+
+#define GET_NIBBLE(n, sha1) (((sha1[n >> 1]) >> ((~n & 0x01) << 2)) & 0x0f)
+
+#define SUBTREE_SHA1_PREFIXCMP(key_sha1, subtree_sha1) \
+	(memcmp(key_sha1, subtree_sha1, subtree_sha1[19]))
+
+static struct int_node root_node;
+
+static int initialized;
+
+static void load_subtree(struct leaf_node *subtree, struct int_node *node,
+		unsigned int n);
+
+/*
+ * Search the tree until the appropriate location for the given key is found:
+ * 1. Start at the root node, with n = 0
+ * 2. If a[0] at the current level is a matching subtree entry, unpack that
+ *    subtree entry and remove it; restart search at the current level.
+ * 3. Use the nth nibble of the key as an index into a:
+ *    - If a[n] is an int_node, recurse from #2 into that node and increment n
+ *    - If a matching subtree entry, unpack that subtree entry (and remove it);
+ *      restart search at the current level.
+ *    - Otherwise, we have found one of the following:
+ *      - a subtree entry which does not match the key
+ *      - a note entry which may or may not match the key
+ *      - an unused leaf node (NULL)
+ *      In any case, set *tree and *n, and return pointer to the tree location.
+ */
+static void **note_tree_search(struct int_node **tree,
+		unsigned char *n, const unsigned char *key_sha1)
+{
+	struct leaf_node *l;
+	unsigned char i;
+	void *p = (*tree)->a[0];
+
+	if (GET_PTR_TYPE(p) == PTR_TYPE_SUBTREE) {
+		l = (struct leaf_node *) CLR_PTR_TYPE(p);
+		if (!SUBTREE_SHA1_PREFIXCMP(key_sha1, l->key_sha1)) {
+			/* unpack tree and resume search */
+			(*tree)->a[0] = NULL;
+			load_subtree(l, *tree, *n);
+			free(l);
+			return note_tree_search(tree, n, key_sha1);
+		}
+	}
+
+	i = GET_NIBBLE(*n, key_sha1);
+	p = (*tree)->a[i];
+	switch(GET_PTR_TYPE(p)) {
+	case PTR_TYPE_INTERNAL:
+		*tree = CLR_PTR_TYPE(p);
+		(*n)++;
+		return note_tree_search(tree, n, key_sha1);
+	case PTR_TYPE_SUBTREE:
+		l = (struct leaf_node *) CLR_PTR_TYPE(p);
+		if (!SUBTREE_SHA1_PREFIXCMP(key_sha1, l->key_sha1)) {
+			/* unpack tree and resume search */
+			(*tree)->a[i] = NULL;
+			load_subtree(l, *tree, *n);
+			free(l);
+			return note_tree_search(tree, n, key_sha1);
+		}
+		/* fall through */
+	default:
+		return &((*tree)->a[i]);
+	}
+}
+
+/*
+ * To find a leaf_node:
+ * Search to the tree location appropriate for the given key:
+ * If a note entry with matching key, return the note entry, else return NULL.
+ */
+static struct leaf_node *note_tree_find(struct int_node *tree, unsigned char n,
+		const unsigned char *key_sha1)
+{
+	void **p = note_tree_search(&tree, &n, key_sha1);
+	if (GET_PTR_TYPE(*p) == PTR_TYPE_NOTE) {
+		struct leaf_node *l = (struct leaf_node *) CLR_PTR_TYPE(*p);
+		if (!hashcmp(key_sha1, l->key_sha1))
+			return l;
+	}
+	return NULL;
+}
+
+/* Create a new blob object by concatenating the two given blob objects */
+static int concatenate_notes(unsigned char *cur_sha1,
+		const unsigned char *new_sha1)
+{
+	char *cur_msg, *new_msg, *buf;
+	unsigned long cur_len, new_len, buf_len;
+	enum object_type cur_type, new_type;
+	int ret;
+
+	/* read in both note blob objects */
+	new_msg = read_sha1_file(new_sha1, &new_type, &new_len);
+	if (!new_msg || !new_len || new_type != OBJ_BLOB) {
+		free(new_msg);
+		return 0;
+	}
+	cur_msg = read_sha1_file(cur_sha1, &cur_type, &cur_len);
+	if (!cur_msg || !cur_len || cur_type != OBJ_BLOB) {
+		free(cur_msg);
+		free(new_msg);
+		hashcpy(cur_sha1, new_sha1);
+		return 0;
+	}
+
+	/* we will separate the notes by a newline anyway */
+	if (cur_msg[cur_len - 1] == '\n')
+		cur_len--;
+
+	/* concatenate cur_msg and new_msg into buf */
+	buf_len = cur_len + 1 + new_len;
+	buf = (char *) xmalloc(buf_len);
+	memcpy(buf, cur_msg, cur_len);
+	buf[cur_len] = '\n';
+	memcpy(buf + cur_len + 1, new_msg, new_len);
+
+	free(cur_msg);
+	free(new_msg);
+
+	/* create a new blob object from buf */
+	ret = write_sha1_file(buf, buf_len, "blob", cur_sha1);
+	free(buf);
+	return ret;
+}
+
+/*
+ * To insert a leaf_node:
+ * Search to the tree location appropriate for the given leaf_node's key:
+ * - If location is unused (NULL), store the tweaked pointer directly there
+ * - If location holds a note entry that matches the note-to-be-inserted, then
+ *   concatenate the two notes.
+ * - If location holds a note entry that matches the subtree-to-be-inserted,
+ *   then unpack the subtree-to-be-inserted into the location.
+ * - If location holds a matching subtree entry, unpack the subtree at that
+ *   location, and restart the insert operation from that level.
+ * - Else, create a new int_node, holding both the node-at-location and the
+ *   node-to-be-inserted, and store the new int_node into the location.
+ */
+static void note_tree_insert(struct int_node *tree, unsigned char n,
+		struct leaf_node *entry, unsigned char type)
+{
+	struct int_node *new_node;
+	struct leaf_node *l;
+	void **p = note_tree_search(&tree, &n, entry->key_sha1);
+
+	assert(GET_PTR_TYPE(entry) == 0); /* no type bits set */
+	l = (struct leaf_node *) CLR_PTR_TYPE(*p);
+	switch(GET_PTR_TYPE(*p)) {
+	case PTR_TYPE_NULL:
+		assert(!*p);
+		*p = SET_PTR_TYPE(entry, type);
+		return;
+	case PTR_TYPE_NOTE:
+		switch (type) {
+		case PTR_TYPE_NOTE:
+			if (!hashcmp(l->key_sha1, entry->key_sha1)) {
+				/* skip concatenation if l == entry */
+				if (!hashcmp(l->val_sha1, entry->val_sha1))
+					return;
+
+				if (concatenate_notes(l->val_sha1,
+						entry->val_sha1))
+					die("failed to concatenate note %s "
+					    "into note %s for commit %s",
+					    sha1_to_hex(entry->val_sha1),
+					    sha1_to_hex(l->val_sha1),
+					    sha1_to_hex(l->key_sha1));
+				free(entry);
+				return;
+			}
+			break;
+		case PTR_TYPE_SUBTREE:
+			if (!SUBTREE_SHA1_PREFIXCMP(l->key_sha1,
+						    entry->key_sha1)) {
+				/* unpack 'entry' */
+				load_subtree(entry, tree, n);
+				free(entry);
+				return;
+			}
+			break;
+		}
+		break;
+	case PTR_TYPE_SUBTREE:
+		if (!SUBTREE_SHA1_PREFIXCMP(entry->key_sha1, l->key_sha1)) {
+			/* unpack 'l' and restart insert */
+			*p = NULL;
+			load_subtree(l, tree, n);
+			free(l);
+			note_tree_insert(tree, n, entry, type);
+			return;
+		}
+		break;
+	}
+
+	/* non-matching leaf_node */
+	assert(GET_PTR_TYPE(*p) == PTR_TYPE_NOTE ||
+	       GET_PTR_TYPE(*p) == PTR_TYPE_SUBTREE);
+	new_node = (struct int_node *) xcalloc(sizeof(struct int_node), 1);
+	note_tree_insert(new_node, n + 1, l, GET_PTR_TYPE(*p));
+	*p = SET_PTR_TYPE(new_node, PTR_TYPE_INTERNAL);
+	note_tree_insert(new_node, n + 1, entry, type);
+}
+
+/* Free the entire notes data contained in the given tree */
+static void note_tree_free(struct int_node *tree)
+{
+	unsigned int i;
+	for (i = 0; i < 16; i++) {
+		void *p = tree->a[i];
+		switch(GET_PTR_TYPE(p)) {
+		case PTR_TYPE_INTERNAL:
+			note_tree_free(CLR_PTR_TYPE(p));
+			/* fall through */
+		case PTR_TYPE_NOTE:
+		case PTR_TYPE_SUBTREE:
+			free(CLR_PTR_TYPE(p));
+		}
+	}
+}
+
+/*
+ * Convert a partial SHA1 hex string to the corresponding partial SHA1 value.
+ * - hex      - Partial SHA1 segment in ASCII hex format
+ * - hex_len  - Length of above segment. Must be multiple of 2 between 0 and 40
+ * - sha1     - Partial SHA1 value is written here
+ * - sha1_len - Max #bytes to store in sha1, Must be >= hex_len / 2, and < 20
+ * Returns -1 on error (invalid arguments or invalid SHA1 (not in hex format).
+ * Otherwise, returns number of bytes written to sha1 (i.e. hex_len / 2).
+ * Pads sha1 with NULs up to sha1_len (not included in returned length).
+ */
+static int get_sha1_hex_segment(const char *hex, unsigned int hex_len,
+		unsigned char *sha1, unsigned int sha1_len)
+{
+	unsigned int i, len = hex_len >> 1;
+	if (hex_len % 2 != 0 || len > sha1_len)
+		return -1;
+	for (i = 0; i < len; i++) {
+		unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
+		if (val & ~0xff)
+			return -1;
+		*sha1++ = val;
+		hex += 2;
+	}
+	for (; i < sha1_len; i++)
+		*sha1++ = 0;
+	return len;
+}
+
+static void load_subtree(struct leaf_node *subtree, struct int_node *node,
+		unsigned int n)
+{
+	unsigned char commit_sha1[20];
+	unsigned int prefix_len;
+	void *buf;
+	struct tree_desc desc;
+	struct name_entry entry;
+
+	buf = fill_tree_descriptor(&desc, subtree->val_sha1);
+	if (!buf)
+		die("Could not read %s for notes-index",
+		     sha1_to_hex(subtree->val_sha1));
+
+	prefix_len = subtree->key_sha1[19];
+	assert(prefix_len * 2 >= n);
+	memcpy(commit_sha1, subtree->key_sha1, prefix_len);
+	while (tree_entry(&desc, &entry)) {
+		int len = get_sha1_hex_segment(entry.path, strlen(entry.path),
+				commit_sha1 + prefix_len, 20 - prefix_len);
+		if (len < 0)
+			continue; /* entry.path is not a SHA1 sum. Skip */
+		len += prefix_len;
+
+		/*
+		 * If commit SHA1 is complete (len == 20), assume note object
+		 * If commit SHA1 is incomplete (len < 20), assume note subtree
+		 */
+		if (len <= 20) {
+			unsigned char type = PTR_TYPE_NOTE;
+			struct leaf_node *l = (struct leaf_node *)
+				xcalloc(sizeof(struct leaf_node), 1);
+			hashcpy(l->key_sha1, commit_sha1);
+			hashcpy(l->val_sha1, entry.sha1);
+			if (len < 20) {
+				l->key_sha1[19] = (unsigned char) len;
+				type = PTR_TYPE_SUBTREE;
+			}
+			note_tree_insert(node, n, l, type);
+		}
+	}
+	free(buf);
+}
+
+static void initialize_notes(const char *notes_ref_name)
+{
+	unsigned char sha1[20], commit_sha1[20];
+	unsigned mode;
+	struct leaf_node root_tree;
+
+	if (!notes_ref_name || read_ref(notes_ref_name, commit_sha1) ||
+	    get_tree_entry(commit_sha1, "", sha1, &mode))
+		return;
+
+	hashclr(root_tree.key_sha1);
+	hashcpy(root_tree.val_sha1, sha1);
+	load_subtree(&root_tree, &root_node, 0);
+}
+
+static unsigned char *lookup_notes(const unsigned char *commit_sha1)
+{
+	struct leaf_node *found = note_tree_find(&root_node, 0, commit_sha1);
+	if (found)
+		return found->val_sha1;
+	return NULL;
+}
+
+void free_notes(void)
+{
+	note_tree_free(&root_node);
+	memset(&root_node, 0, sizeof(struct int_node));
+	initialized = 0;
+}
+
+void get_commit_notes(const struct commit *commit, struct strbuf *sb,
+		const char *output_encoding, int flags)
+{
+	static const char utf8[] = "utf-8";
+	unsigned char *sha1;
+	char *msg, *msg_p;
+	unsigned long linelen, msglen;
+	enum object_type type;
+
+	if (!initialized) {
+		const char *env = getenv(GIT_NOTES_REF_ENVIRONMENT);
+		if (env)
+			notes_ref_name = getenv(GIT_NOTES_REF_ENVIRONMENT);
+		else if (!notes_ref_name)
+			notes_ref_name = GIT_NOTES_DEFAULT_REF;
+		initialize_notes(notes_ref_name);
+		initialized = 1;
+	}
+
+	sha1 = lookup_notes(commit->object.sha1);
+	if (!sha1)
+		return;
+
+	if (!(msg = read_sha1_file(sha1, &type, &msglen)) || !msglen ||
+			type != OBJ_BLOB) {
+		free(msg);
+		return;
+	}
+
+	if (output_encoding && *output_encoding &&
+			strcmp(utf8, output_encoding)) {
+		char *reencoded = reencode_string(msg, output_encoding, utf8);
+		if (reencoded) {
+			free(msg);
+			msg = reencoded;
+			msglen = strlen(msg);
+		}
+	}
+
+	/* we will end the annotation by a newline anyway */
+	if (msglen && msg[msglen - 1] == '\n')
+		msglen--;
+
+	if (flags & NOTES_SHOW_HEADER)
+		strbuf_addstr(sb, "\nNotes:\n");
+
+	for (msg_p = msg; msg_p < msg + msglen; msg_p += linelen + 1) {
+		linelen = strchrnul(msg_p, '\n') - msg_p;
+
+		if (flags & NOTES_INDENT)
+			strbuf_addstr(sb, "    ");
+		strbuf_add(sb, msg_p, linelen);
+		strbuf_addch(sb, '\n');
+	}
+
+	free(msg);
+}
diff --git a/notes.h b/notes.h
new file mode 100644
index 0000000000..a1421e351a
--- /dev/null
+++ b/notes.h
@@ -0,0 +1,13 @@
+#ifndef NOTES_H
+#define NOTES_H
+
+/* Free (and de-initialize) the internal notes tree structure */
+void free_notes(void);
+
+#define NOTES_SHOW_HEADER 1
+#define NOTES_INDENT 2
+
+void get_commit_notes(const struct commit *commit, struct strbuf *sb,
+		const char *output_encoding, int flags);
+
+#endif
diff --git a/pretty.c b/pretty.c
index 2e031e62fd..5661cba595 100644
--- a/pretty.c
+++ b/pretty.c
@@ -6,6 +6,7 @@
 #include "string-list.h"
 #include "mailmap.h"
 #include "log-tree.h"
+#include "notes.h"
 #include "color.h"
 #include "reflog-walk.h"
 
@@ -773,6 +774,10 @@ static size_t format_commit_item(struct strbuf *sb, const char *placeholder,
 			return 2;
 		}
 		return 0;	/* unknown %g placeholder */
+	case 'N':
+		get_commit_notes(commit, sb, git_log_output_encoding ?
+			     git_log_output_encoding : git_commit_encoding, 0);
+		return 1;
 	}
 
 	/* For the rest we have to parse the commit header. */
@@ -1050,5 +1055,10 @@ void pretty_print_commit(enum cmit_fmt fmt, const struct commit *commit,
 	 */
 	if (fmt == CMIT_FMT_EMAIL && sb->len <= beginning_of_body)
 		strbuf_addch(sb, '\n');
+
+	if (fmt != CMIT_FMT_ONELINE)
+		get_commit_notes(commit, sb, encoding,
+				 NOTES_SHOW_HEADER | NOTES_INDENT);
+
 	free(reencoded);
 }
diff --git a/t/t3301-notes.sh b/t/t3301-notes.sh
new file mode 100755
index 0000000000..1e34f4836f
--- /dev/null
+++ b/t/t3301-notes.sh
@@ -0,0 +1,150 @@
+#!/bin/sh
+#
+# Copyright (c) 2007 Johannes E. Schindelin
+#
+
+test_description='Test commit notes'
+
+. ./test-lib.sh
+
+cat > fake_editor.sh << \EOF
+echo "$MSG" > "$1"
+echo "$MSG" >& 2
+EOF
+chmod a+x fake_editor.sh
+VISUAL=./fake_editor.sh
+export VISUAL
+
+test_expect_success 'cannot annotate non-existing HEAD' '
+	(MSG=3 && export MSG && test_must_fail git notes edit)
+'
+
+test_expect_success setup '
+	: > a1 &&
+	git add a1 &&
+	test_tick &&
+	git commit -m 1st &&
+	: > a2 &&
+	git add a2 &&
+	test_tick &&
+	git commit -m 2nd
+'
+
+test_expect_success 'need valid notes ref' '
+	(MSG=1 GIT_NOTES_REF=/ && export MSG GIT_NOTES_REF &&
+	 test_must_fail git notes edit) &&
+	(MSG=2 GIT_NOTES_REF=/ && export MSG GIT_NOTES_REF &&
+	 test_must_fail git notes show)
+'
+
+test_expect_success 'refusing to edit in refs/heads/' '
+	(MSG=1 GIT_NOTES_REF=refs/heads/bogus &&
+	 export MSG GIT_NOTES_REF &&
+	 test_must_fail git notes edit)
+'
+
+test_expect_success 'refusing to edit in refs/remotes/' '
+	(MSG=1 GIT_NOTES_REF=refs/remotes/bogus &&
+	 export MSG GIT_NOTES_REF &&
+	 test_must_fail git notes edit)
+'
+
+# 1 indicates caught gracefully by die, 128 means git-show barked
+test_expect_success 'handle empty notes gracefully' '
+	git notes show ; test 1 = $?
+'
+
+test_expect_success 'create notes' '
+	git config core.notesRef refs/notes/commits &&
+	MSG=b1 git notes edit &&
+	test ! -f .git/new-notes &&
+	test 1 = $(git ls-tree refs/notes/commits | wc -l) &&
+	test b1 = $(git notes show) &&
+	git show HEAD^ &&
+	test_must_fail git notes show HEAD^
+'
+
+cat > expect << EOF
+commit 268048bfb8a1fb38e703baceb8ab235421bf80c5
+Author: A U Thor <author@example.com>
+Date:   Thu Apr 7 15:14:13 2005 -0700
+
+    2nd
+
+Notes:
+    b1
+EOF
+
+test_expect_success 'show notes' '
+	! (git cat-file commit HEAD | grep b1) &&
+	git log -1 > output &&
+	test_cmp expect output
+'
+test_expect_success 'create multi-line notes (setup)' '
+	: > a3 &&
+	git add a3 &&
+	test_tick &&
+	git commit -m 3rd &&
+	MSG="b3
+c3c3c3c3
+d3d3d3" git notes edit
+'
+
+cat > expect-multiline << EOF
+commit 1584215f1d29c65e99c6c6848626553fdd07fd75
+Author: A U Thor <author@example.com>
+Date:   Thu Apr 7 15:15:13 2005 -0700
+
+    3rd
+
+Notes:
+    b3
+    c3c3c3c3
+    d3d3d3
+EOF
+
+printf "\n" >> expect-multiline
+cat expect >> expect-multiline
+
+test_expect_success 'show multi-line notes' '
+	git log -2 > output &&
+	test_cmp expect-multiline output
+'
+test_expect_success 'create -m and -F notes (setup)' '
+	: > a4 &&
+	git add a4 &&
+	test_tick &&
+	git commit -m 4th &&
+	echo "xyzzy" > note5 &&
+	git notes edit -m spam -F note5 -m "foo
+bar
+baz"
+'
+
+whitespace="    "
+cat > expect-m-and-F << EOF
+commit 15023535574ded8b1a89052b32673f84cf9582b8
+Author: A U Thor <author@example.com>
+Date:   Thu Apr 7 15:16:13 2005 -0700
+
+    4th
+
+Notes:
+    spam
+$whitespace
+    xyzzy
+$whitespace
+    foo
+    bar
+    baz
+EOF
+
+printf "\n" >> expect-m-and-F
+cat expect-multiline >> expect-m-and-F
+
+test_expect_success 'show -m and -F notes' '
+	git log -3 > output &&
+	test_cmp expect-m-and-F output
+'
+
+test_done
diff --git a/t/t3302-notes-index-expensive.sh b/t/t3302-notes-index-expensive.sh
new file mode 100755
index 0000000000..ee84fc4884
--- /dev/null
+++ b/t/t3302-notes-index-expensive.sh
@@ -0,0 +1,118 @@
+#!/bin/sh
+#
+# Copyright (c) 2007 Johannes E. Schindelin
+#
+
+test_description='Test commit notes index (expensive!)'
+
+. ./test-lib.sh
+
+test -z "$GIT_NOTES_TIMING_TESTS" && {
+	say Skipping timing tests
+	test_done
+	exit
+}
+
+create_repo () {
+	number_of_commits=$1
+	nr=0
+	test -d .git || {
+	git init &&
+	(
+		while [ $nr -lt $number_of_commits ]; do
+			nr=$(($nr+1))
+			mark=$(($nr+$nr))
+			notemark=$(($mark+1))
+			test_tick &&
+			cat <<INPUT_END &&
+commit refs/heads/master
+mark :$mark
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+commit #$nr
+COMMIT
+
+M 644 inline file
+data <<EOF
+file in commit #$nr
+EOF
+
+blob
+mark :$notemark
+data <<EOF
+note for commit #$nr
+EOF
+
+INPUT_END
+
+			echo "N :$notemark :$mark" >> note_commit
+		done &&
+		test_tick &&
+		cat <<INPUT_END &&
+commit refs/notes/commits
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+notes
+COMMIT
+
+INPUT_END
+
+		cat note_commit
+	) |
+	git fast-import --quiet &&
+	git config core.notesRef refs/notes/commits
+	}
+}
+
+test_notes () {
+	count=$1 &&
+	git config core.notesRef refs/notes/commits &&
+	git log | grep "^    " > output &&
+	i=$count &&
+	while [ $i -gt 0 ]; do
+		echo "    commit #$i" &&
+		echo "    note for commit #$i" &&
+		i=$(($i-1));
+	done > expect &&
+	test_cmp expect output
+}
+
+cat > time_notes << \EOF
+	mode=$1
+	i=1
+	while [ $i -lt $2 ]; do
+		case $1 in
+		no-notes)
+			GIT_NOTES_REF=non-existing; export GIT_NOTES_REF
+		;;
+		notes)
+			unset GIT_NOTES_REF
+		;;
+		esac
+		git log >/dev/null
+		i=$(($i+1))
+	done
+EOF
+
+time_notes () {
+	for mode in no-notes notes
+	do
+		echo $mode
+		/usr/bin/time sh ../time_notes $mode $1
+	done
+}
+
+for count in 10 100 1000 10000; do
+
+	mkdir $count
+	(cd $count;
+
+	test_expect_success "setup $count" "create_repo $count"
+
+	test_expect_success 'notes work' "test_notes $count"
+
+	test_expect_success 'notes timing' "time_notes 100"
+	)
+done
+
+test_done
diff --git a/t/t3303-notes-subtrees.sh b/t/t3303-notes-subtrees.sh
new file mode 100755
index 0000000000..edc4bc8841
--- /dev/null
+++ b/t/t3303-notes-subtrees.sh
@@ -0,0 +1,188 @@
+#!/bin/sh
+
+test_description='Test commit notes organized in subtrees'
+
+. ./test-lib.sh
+
+number_of_commits=100
+
+start_note_commit () {
+	test_tick &&
+	cat <<INPUT_END
+commit refs/notes/commits
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+notes
+COMMIT
+
+from refs/notes/commits^0
+deleteall
+INPUT_END
+
+}
+
+verify_notes () {
+	git log | grep "^    " > output &&
+	i=$number_of_commits &&
+	while [ $i -gt 0 ]; do
+		echo "    commit #$i" &&
+		echo "    note for commit #$i" &&
+		i=$(($i-1));
+	done > expect &&
+	test_cmp expect output
+}
+
+test_expect_success "setup: create $number_of_commits commits" '
+
+	(
+		nr=0 &&
+		while [ $nr -lt $number_of_commits ]; do
+			nr=$(($nr+1)) &&
+			test_tick &&
+			cat <<INPUT_END
+commit refs/heads/master
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+commit #$nr
+COMMIT
+
+M 644 inline file
+data <<EOF
+file in commit #$nr
+EOF
+
+INPUT_END
+
+		done &&
+		test_tick &&
+		cat <<INPUT_END
+commit refs/notes/commits
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+no notes
+COMMIT
+
+deleteall
+
+INPUT_END
+
+	) |
+	git fast-import --quiet &&
+	git config core.notesRef refs/notes/commits
+'
+
+test_sha1_based () {
+	(
+		start_note_commit &&
+		nr=$number_of_commits &&
+		git rev-list refs/heads/master |
+		while read sha1; do
+			note_path=$(echo "$sha1" | sed "$1")
+			cat <<INPUT_END &&
+M 100644 inline $note_path
+data <<EOF
+note for commit #$nr
+EOF
+
+INPUT_END
+
+			nr=$(($nr-1))
+		done
+	) |
+	git fast-import --quiet
+}
+
+test_expect_success 'test notes in 2/38-fanout' 'test_sha1_based "s|^..|&/|"'
+test_expect_success 'verify notes in 2/38-fanout' 'verify_notes'
+
+test_expect_success 'test notes in 4/36-fanout' 'test_sha1_based "s|^....|&/|"'
+test_expect_success 'verify notes in 4/36-fanout' 'verify_notes'
+
+test_expect_success 'test notes in 2/2/36-fanout' 'test_sha1_based "s|^\(..\)\(..\)|\1/\2/|"'
+test_expect_success 'verify notes in 2/2/36-fanout' 'verify_notes'
+
+test_same_notes () {
+	(
+		start_note_commit &&
+		nr=$number_of_commits &&
+		git rev-list refs/heads/master |
+		while read sha1; do
+			first_note_path=$(echo "$sha1" | sed "$1")
+			second_note_path=$(echo "$sha1" | sed "$2")
+			cat <<INPUT_END &&
+M 100644 inline $second_note_path
+data <<EOF
+note for commit #$nr
+EOF
+
+M 100644 inline $first_note_path
+data <<EOF
+note for commit #$nr
+EOF
+
+INPUT_END
+
+			nr=$(($nr-1))
+		done
+	) |
+	git fast-import --quiet
+}
+
+test_expect_success 'test same notes in 4/36-fanout and 2/38-fanout' 'test_same_notes "s|^..|&/|" "s|^....|&/|"'
+test_expect_success 'verify same notes in 4/36-fanout and 2/38-fanout' 'verify_notes'
+
+test_expect_success 'test same notes in 2/38-fanout and 2/2/36-fanout' 'test_same_notes "s|^\(..\)\(..\)|\1/\2/|" "s|^..|&/|"'
+test_expect_success 'verify same notes in 2/38-fanout and 2/2/36-fanout' 'verify_notes'
+
+test_expect_success 'test same notes in 4/36-fanout and 2/2/36-fanout' 'test_same_notes "s|^\(..\)\(..\)|\1/\2/|" "s|^....|&/|"'
+test_expect_success 'verify same notes in 4/36-fanout and 2/2/36-fanout' 'verify_notes'
+
+test_concatenated_notes () {
+	(
+		start_note_commit &&
+		nr=$number_of_commits &&
+		git rev-list refs/heads/master |
+		while read sha1; do
+			first_note_path=$(echo "$sha1" | sed "$1")
+			second_note_path=$(echo "$sha1" | sed "$2")
+			cat <<INPUT_END &&
+M 100644 inline $second_note_path
+data <<EOF
+second note for commit #$nr
+EOF
+
+M 100644 inline $first_note_path
+data <<EOF
+first note for commit #$nr
+EOF
+
+INPUT_END
+
+			nr=$(($nr-1))
+		done
+	) |
+	git fast-import --quiet
+}
+
+verify_concatenated_notes () {
+    git log | grep "^    " > output &&
+    i=$number_of_commits &&
+    while [ $i -gt 0 ]; do
+        echo "    commit #$i" &&
+        echo "    first note for commit #$i" &&
+        echo "    second note for commit #$i" &&
+        i=$(($i-1));
+    done > expect &&
+    test_cmp expect output
+}
+
+test_expect_success 'test notes in 4/36-fanout concatenated with 2/38-fanout' 'test_concatenated_notes "s|^..|&/|" "s|^....|&/|"'
+test_expect_success 'verify notes in 4/36-fanout concatenated with 2/38-fanout' 'verify_concatenated_notes'
+
+test_expect_success 'test notes in 2/38-fanout concatenated with 2/2/36-fanout' 'test_concatenated_notes "s|^\(..\)\(..\)|\1/\2/|" "s|^..|&/|"'
+test_expect_success 'verify notes in 2/38-fanout concatenated with 2/2/36-fanout' 'verify_concatenated_notes'
+
+test_expect_success 'test notes in 4/36-fanout concatenated with 2/2/36-fanout' 'test_concatenated_notes "s|^\(..\)\(..\)|\1/\2/|" "s|^....|&/|"'
+test_expect_success 'verify notes in 4/36-fanout concatenated with 2/2/36-fanout' 'verify_concatenated_notes'
+
+test_done
diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index 821be7ce8d..b49815d108 100755
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -1088,4 +1088,170 @@ INPUT_END
 test_expect_success 'P: fail on blob mark in gitlink' '
     test_must_fail git fast-import <input'
 
+###
+### series Q (notes)
+###
+
+note1_data="Note for the first commit"
+note2_data="Note for the second commit"
+note3_data="Note for the third commit"
+
+test_tick
+cat >input <<INPUT_END
+blob
+mark :2
+data <<EOF
+$file2_data
+EOF
+
+commit refs/heads/notes-test
+mark :3
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+first (:3)
+COMMIT
+
+M 644 :2 file2
+
+blob
+mark :4
+data $file4_len
+$file4_data
+commit refs/heads/notes-test
+mark :5
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+second (:5)
+COMMIT
+
+M 644 :4 file4
+
+commit refs/heads/notes-test
+mark :6
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+third (:6)
+COMMIT
+
+M 644 inline file5
+data <<EOF
+$file5_data
+EOF
+
+M 755 inline file6
+data <<EOF
+$file6_data
+EOF
+
+blob
+mark :7
+data <<EOF
+$note1_data
+EOF
+
+blob
+mark :8
+data <<EOF
+$note2_data
+EOF
+
+commit refs/notes/foobar
+mark :9
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+data <<COMMIT
+notes (:9)
+COMMIT
+
+N :7 :3
+N :8 :5
+N inline :6
+data <<EOF
+$note3_data
+EOF
+
+INPUT_END
+test_expect_success \
+	'Q: commit notes' \
+	'git fast-import <input &&
+	 git whatchanged notes-test'
+test_expect_success \
+	'Q: verify pack' \
+	'for p in .git/objects/pack/*.pack;do git verify-pack $p||exit;done'
+
+commit1=$(git rev-parse notes-test~2)
+commit2=$(git rev-parse notes-test^)
+commit3=$(git rev-parse notes-test)
+
+cat >expect <<EOF
+author $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+
+first (:3)
+EOF
+test_expect_success \
+	'Q: verify first commit' \
+	'git cat-file commit notes-test~2 | sed 1d >actual &&
+	test_cmp expect actual'
+
+cat >expect <<EOF
+parent $commit1
+author $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+
+second (:5)
+EOF
+test_expect_success \
+	'Q: verify second commit' \
+	'git cat-file commit notes-test^ | sed 1d >actual &&
+	test_cmp expect actual'
+
+cat >expect <<EOF
+parent $commit2
+author $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+
+third (:6)
+EOF
+test_expect_success \
+	'Q: verify third commit' \
+	'git cat-file commit notes-test | sed 1d >actual &&
+	test_cmp expect actual'
+
+cat >expect <<EOF
+author $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+committer $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> $GIT_COMMITTER_DATE
+
+notes (:9)
+EOF
+test_expect_success \
+	'Q: verify notes commit' \
+	'git cat-file commit refs/notes/foobar | sed 1d >actual &&
+	test_cmp expect actual'
+
+cat >expect.unsorted <<EOF
+100644 blob $commit1
+100644 blob $commit2
+100644 blob $commit3
+EOF
+cat expect.unsorted | sort >expect
+test_expect_success \
+	'Q: verify notes tree' \
+	'git cat-file -p refs/notes/foobar^{tree} | sed "s/ [0-9a-f]*	/ /" >actual &&
+	 test_cmp expect actual'
+
+echo "$note1_data" >expect
+test_expect_success \
+	'Q: verify note for first commit' \
+	'git cat-file blob refs/notes/foobar:$commit1 >actual && test_cmp expect actual'
+
+echo "$note2_data" >expect
+test_expect_success \
+	'Q: verify note for second commit' \
+	'git cat-file blob refs/notes/foobar:$commit2 >actual && test_cmp expect actual'
+
+echo "$note3_data" >expect
+test_expect_success \
+	'Q: verify note for third commit' \
+	'git cat-file blob refs/notes/foobar:$commit3 >actual && test_cmp expect actual'
+
 test_done