Merge branch 'jk/diff-submodule-diff-inline'

The "git diff --submodule={short,log}" mechanism has been enhanced
to allow "--submodule=diff" to show the patch between the submodule
commits bound to the superproject.

* jk/diff-submodule-diff-inline:
  diff: teach diff to display submodule difference with an inline diff
  submodule: refactor show_submodule_summary with helper function
  submodule: convert show_submodule_summary to use struct object_id *
  allow do_submodule_path to work even if submodule isn't checked out
  diff: prepare for additional submodule formats
  graph: add support for --line-prefix on all graph-aware output
  diff.c: remove output_prefix_length field
  cache: add empty_tree_oid object and helper function

20 files changed, 1663 insertions, 161 deletions

diff --git a/Documentation/diff-config.txt b/Documentation/diff-config.txt
index d5a5b17d50..0eded24034 100644
--- a/Documentation/diff-config.txt
+++ b/Documentation/diff-config.txt
@@ -122,10 +122,11 @@ diff.suppressBlankEmpty::
 
 diff.submodule::
 	Specify the format in which differences in submodules are
-	shown.  The "log" format lists the commits in the range like
-	linkgit:git-submodule[1] `summary` does.  The "short" format
-	format just shows the names of the commits at the beginning
-	and end of the range.  Defaults to short.
+	shown.  The "short" format just shows the names of the commits
+	at the beginning and end of the range. The "log" format lists
+	the commits in the range like linkgit:git-submodule[1] `summary`
+	does. The "diff" format shows an inline diff of the changed
+	contents of the submodule. Defaults to "short".
 
 diff.wordRegex::
 	A POSIX Extended Regular Expression used to determine what is a "word"
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 705a873942..7805a0ccad 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -210,13 +210,16 @@ any of those replacements occurred.
 	of the `--diff-filter` option on what the status letters mean.
 
 --submodule[=<format>]::
-	Specify how differences in submodules are shown.  When `--submodule`
-	or `--submodule=log` is given, the 'log' format is used.  This format lists
-	the commits in the range like linkgit:git-submodule[1] `summary` does.
-	Omitting the `--submodule` option or specifying `--submodule=short`,
-	uses the 'short' format. This format just shows the names of the commits
-	at the beginning and end of the range.  Can be tweaked via the
-	`diff.submodule` configuration variable.
+	Specify how differences in submodules are shown.  When specifying
+	`--submodule=short` the 'short' format is used.  This format just
+	shows the names of the commits at the beginning and end of the range.
+	When `--submodule` or `--submodule=log` is specified, the 'log'
+	format is used.  This format lists the commits in the range like
+	linkgit:git-submodule[1] `summary` does.  When `--submodule=diff`
+	is specified, the 'diff' format is used.  This format shows an
+	inline diff of the changes in the submodule contents between the
+	commit range.  Defaults to `diff.submodule` or the 'short' format
+	if the config option is unset.
 
 --color[=<when>]::
 	Show colored diff.
@@ -569,5 +572,8 @@ endif::git-format-patch[]
 --no-prefix::
 	Do not show any source or destination prefix.
 
+--line-prefix=<prefix>::
+	Prepend an additional prefix to every line of output.
+
 For more detailed explanation on these common options, see also
 linkgit:gitdiffcore[7].
diff --git a/builtin/rev-list.c b/builtin/rev-list.c
index 0ba82b1635..8479f6ed28 100644
--- a/builtin/rev-list.c
+++ b/builtin/rev-list.c
@@ -122,48 +122,40 @@ static void show_commit(struct commit *commit, void *data)
 		ctx.fmt = revs->commit_format;
 		ctx.output_encoding = get_log_output_encoding();
 		pretty_print_commit(&ctx, commit, &buf);
-		if (revs->graph) {
-			if (buf.len) {
-				if (revs->commit_format != CMIT_FMT_ONELINE)
-					graph_show_oneline(revs->graph);
-
-				graph_show_commit_msg(revs->graph, &buf);
-
-				/*
-				 * Add a newline after the commit message.
-				 *
-				 * Usually, this newline produces a blank
-				 * padding line between entries, in which case
-				 * we need to add graph padding on this line.
-				 *
-				 * However, the commit message may not end in a
-				 * newline.  In this case the newline simply
-				 * ends the last line of the commit message,
-				 * and we don't need any graph output.  (This
-				 * always happens with CMIT_FMT_ONELINE, and it
-				 * happens with CMIT_FMT_USERFORMAT when the
-				 * format doesn't explicitly end in a newline.)
-				 */
-				if (buf.len && buf.buf[buf.len - 1] == '\n')
-					graph_show_padding(revs->graph);
-				putchar('\n');
-			} else {
-				/*
-				 * If the message buffer is empty, just show
-				 * the rest of the graph output for this
-				 * commit.
-				 */
-				if (graph_show_remainder(revs->graph))
-					putchar('\n');
-				if (revs->commit_format == CMIT_FMT_ONELINE)
-					putchar('\n');
-			}
+		if (buf.len) {
+			if (revs->commit_format != CMIT_FMT_ONELINE)
+				graph_show_oneline(revs->graph);
+
+			graph_show_commit_msg(revs->graph, stdout, &buf);
+
+			/*
+			 * Add a newline after the commit message.
+			 *
+			 * Usually, this newline produces a blank
+			 * padding line between entries, in which case
+			 * we need to add graph padding on this line.
+			 *
+			 * However, the commit message may not end in a
+			 * newline.  In this case the newline simply
+			 * ends the last line of the commit message,
+			 * and we don't need any graph output.  (This
+			 * always happens with CMIT_FMT_ONELINE, and it
+			 * happens with CMIT_FMT_USERFORMAT when the
+			 * format doesn't explicitly end in a newline.)
+			 */
+			if (buf.len && buf.buf[buf.len - 1] == '\n')
+				graph_show_padding(revs->graph);
+			putchar('\n');
 		} else {
-			if (revs->commit_format != CMIT_FMT_USERFORMAT ||
-			    buf.len) {
-				fwrite(buf.buf, 1, buf.len, stdout);
-				putchar(info->hdr_termination);
-			}
+			/*
+			 * If the message buffer is empty, just show
+			 * the rest of the graph output for this
+			 * commit.
+			 */
+			if (graph_show_remainder(revs->graph))
+				putchar('\n');
+			if (revs->commit_format == CMIT_FMT_ONELINE)
+				putchar('\n');
 		}
 		strbuf_release(&buf);
 	} else {
diff --git a/cache.h b/cache.h
index 6738050132..aac38a6b99 100644
--- a/cache.h
+++ b/cache.h
@@ -819,8 +819,8 @@ extern void strbuf_git_common_path(struct strbuf *sb, const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
 extern char *git_path_buf(struct strbuf *buf, const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
-extern void strbuf_git_path_submodule(struct strbuf *sb, const char *path,
-				      const char *fmt, ...)
+extern int strbuf_git_path_submodule(struct strbuf *sb, const char *path,
+				     const char *fmt, ...)
 	__attribute__((format (printf, 3, 4)));
 extern char *git_pathdup(const char *fmt, ...)
 	__attribute__((format (printf, 1, 2)));
@@ -953,22 +953,39 @@ static inline void oidclr(struct object_id *oid)
 #define EMPTY_TREE_SHA1_BIN_LITERAL \
 	 "\x4b\x82\x5d\xc6\x42\xcb\x6e\xb9\xa0\x60" \
 	 "\xe5\x4b\xf8\xd6\x92\x88\xfb\xee\x49\x04"
-#define EMPTY_TREE_SHA1_BIN \
-	 ((const unsigned char *) EMPTY_TREE_SHA1_BIN_LITERAL)
+extern const struct object_id empty_tree_oid;
+#define EMPTY_TREE_SHA1_BIN (empty_tree_oid.hash)
 
 #define EMPTY_BLOB_SHA1_HEX \
 	"e69de29bb2d1d6434b8b29ae775ad8c2e48c5391"
 #define EMPTY_BLOB_SHA1_BIN_LITERAL \
 	"\xe6\x9d\xe2\x9b\xb2\xd1\xd6\x43\x4b\x8b" \
 	"\x29\xae\x77\x5a\xd8\xc2\xe4\x8c\x53\x91"
-#define EMPTY_BLOB_SHA1_BIN \
-	((const unsigned char *) EMPTY_BLOB_SHA1_BIN_LITERAL)
+extern const struct object_id empty_blob_oid;
+#define EMPTY_BLOB_SHA1_BIN (empty_blob_oid.hash)
+
 
 static inline int is_empty_blob_sha1(const unsigned char *sha1)
 {
 	return !hashcmp(sha1, EMPTY_BLOB_SHA1_BIN);
 }
 
+static inline int is_empty_blob_oid(const struct object_id *oid)
+{
+	return !hashcmp(oid->hash, EMPTY_BLOB_SHA1_BIN);
+}
+
+static inline int is_empty_tree_sha1(const unsigned char *sha1)
+{
+	return !hashcmp(sha1, EMPTY_TREE_SHA1_BIN);
+}
+
+static inline int is_empty_tree_oid(const struct object_id *oid)
+{
+	return !hashcmp(oid->hash, EMPTY_TREE_SHA1_BIN);
+}
+
+
 int git_mkstemp(char *path, size_t n, const char *template);
 
 /* set default permissions by passing mode arguments to open(2) */
diff --git a/diff.c b/diff.c
index 534c12e28e..b38d95eb24 100644
--- a/diff.c
+++ b/diff.c
@@ -18,6 +18,7 @@
 #include "ll-merge.h"
 #include "string-list.h"
 #include "argv-array.h"
+#include "graph.h"
 
 #ifdef NO_FAST_WORKING_DIRECTORY
 #define FAST_WORKING_DIRECTORY 0
@@ -131,9 +132,11 @@ static int parse_dirstat_params(struct diff_options *options, const char *params
 static int parse_submodule_params(struct diff_options *options, const char *value)
 {
 	if (!strcmp(value, "log"))
-		DIFF_OPT_SET(options, SUBMODULE_LOG);
+		options->submodule_format = DIFF_SUBMODULE_LOG;
 	else if (!strcmp(value, "short"))
-		DIFF_OPT_CLR(options, SUBMODULE_LOG);
+		options->submodule_format = DIFF_SUBMODULE_SHORT;
+	else if (!strcmp(value, "diff"))
+		options->submodule_format = DIFF_SUBMODULE_INLINE_DIFF;
 	else
 		return -1;
 	return 0;
@@ -1625,7 +1628,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	 */
 
 	if (options->stat_width == -1)
-		width = term_columns() - options->output_prefix_length;
+		width = term_columns() - strlen(line_prefix);
 	else
 		width = options->stat_width ? options->stat_width : 80;
 	number_width = decimal_width(max_change) > number_width ?
@@ -2299,17 +2302,37 @@ static void builtin_diff(const char *name_a,
 	struct strbuf header = STRBUF_INIT;
 	const char *line_prefix = diff_line_prefix(o);
 
-	if (DIFF_OPT_TST(o, SUBMODULE_LOG) &&
-			(!one->mode || S_ISGITLINK(one->mode)) &&
-			(!two->mode || S_ISGITLINK(two->mode))) {
+	diff_set_mnemonic_prefix(o, "a/", "b/");
+	if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
+		a_prefix = o->b_prefix;
+		b_prefix = o->a_prefix;
+	} else {
+		a_prefix = o->a_prefix;
+		b_prefix = o->b_prefix;
+	}
+
+	if (o->submodule_format == DIFF_SUBMODULE_LOG &&
+	    (!one->mode || S_ISGITLINK(one->mode)) &&
+	    (!two->mode || S_ISGITLINK(two->mode))) {
 		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
 		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
 		show_submodule_summary(o->file, one->path ? one->path : two->path,
 				line_prefix,
-				one->oid.hash, two->oid.hash,
+				&one->oid, &two->oid,
 				two->dirty_submodule,
 				meta, del, add, reset);
 		return;
+	} else if (o->submodule_format == DIFF_SUBMODULE_INLINE_DIFF &&
+		   (!one->mode || S_ISGITLINK(one->mode)) &&
+		   (!two->mode || S_ISGITLINK(two->mode))) {
+		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
+		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
+		show_submodule_inline_diff(o->file, one->path ? one->path : two->path,
+				line_prefix,
+				&one->oid, &two->oid,
+				two->dirty_submodule,
+				meta, del, add, reset, o);
+		return;
 	}
 
 	if (DIFF_OPT_TST(o, ALLOW_TEXTCONV)) {
@@ -2317,15 +2340,6 @@ static void builtin_diff(const char *name_a,
 		textconv_two = get_textconv(two);
 	}
 
-	diff_set_mnemonic_prefix(o, "a/", "b/");
-	if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
-		a_prefix = o->b_prefix;
-		b_prefix = o->a_prefix;
-	} else {
-		a_prefix = o->a_prefix;
-		b_prefix = o->b_prefix;
-	}
-
 	/* Never use a non-valid filename anywhere if at all possible */
 	name_a = DIFF_FILE_VALID(one) ? name_a : name_b;
 	name_b = DIFF_FILE_VALID(two) ? name_b : name_a;
@@ -3915,7 +3929,7 @@ int diff_opt_parse(struct diff_options *options,
 		DIFF_OPT_SET(options, OVERRIDE_SUBMODULE_CONFIG);
 		handle_ignore_submodules_arg(options, arg);
 	} else if (!strcmp(arg, "--submodule"))
-		DIFF_OPT_SET(options, SUBMODULE_LOG);
+		options->submodule_format = DIFF_SUBMODULE_LOG;
 	else if (skip_prefix(arg, "--submodule=", &arg))
 		return parse_submodule_opt(options, arg);
 	else if (skip_prefix(arg, "--ws-error-highlight=", &arg))
@@ -3966,6 +3980,12 @@ int diff_opt_parse(struct diff_options *options,
 		options->a_prefix = optarg;
 		return argcount;
 	}
+	else if ((argcount = parse_long_opt("line-prefix", av, &optarg))) {
+		options->line_prefix = optarg;
+		options->line_prefix_length = strlen(options->line_prefix);
+		graph_setup_line_prefix(options);
+		return argcount;
+	}
 	else if ((argcount = parse_long_opt("dst-prefix", av, &optarg))) {
 		options->b_prefix = optarg;
 		return argcount;
diff --git a/diff.h b/diff.h
index 7883729edf..ec76a90522 100644
--- a/diff.h
+++ b/diff.h
@@ -83,7 +83,6 @@ typedef struct strbuf *(*diff_prefix_fn_t)(struct diff_options *opt, void *data)
 #define DIFF_OPT_DIRSTAT_BY_FILE     (1 << 20)
 #define DIFF_OPT_ALLOW_TEXTCONV      (1 << 21)
 #define DIFF_OPT_DIFF_FROM_CONTENTS  (1 << 22)
-#define DIFF_OPT_SUBMODULE_LOG       (1 << 23)
 #define DIFF_OPT_DIRTY_SUBMODULES    (1 << 24)
 #define DIFF_OPT_IGNORE_UNTRACKED_IN_SUBMODULES (1 << 25)
 #define DIFF_OPT_IGNORE_DIRTY_SUBMODULES (1 << 26)
@@ -110,11 +109,19 @@ enum diff_words_type {
 	DIFF_WORDS_COLOR
 };
 
+enum diff_submodule_format {
+	DIFF_SUBMODULE_SHORT = 0,
+	DIFF_SUBMODULE_LOG,
+	DIFF_SUBMODULE_INLINE_DIFF
+};
+
 struct diff_options {
 	const char *orderfile;
 	const char *pickaxe;
 	const char *single_follow;
 	const char *a_prefix, *b_prefix;
+	const char *line_prefix;
+	size_t line_prefix_length;
 	unsigned flags;
 	unsigned touched_flags;
 
@@ -155,6 +162,7 @@ struct diff_options {
 	int stat_count;
 	const char *word_regex;
 	enum diff_words_type word_diff;
+	enum diff_submodule_format submodule_format;
 
 	/* this is set by diffcore for DIFF_FORMAT_PATCH */
 	int found_changes;
@@ -174,7 +182,6 @@ struct diff_options {
 	diff_format_fn_t format_callback;
 	void *format_callback_data;
 	diff_prefix_fn_t output_prefix;
-	int output_prefix_length;
 	void *output_prefix_data;
 
 	int diff_path_counter;
diff --git a/graph.c b/graph.c
index dd1720148d..06f1139f2e 100644
--- a/graph.c
+++ b/graph.c
@@ -2,7 +2,6 @@
 #include "commit.h"
 #include "color.h"
 #include "graph.h"
-#include "diff.h"
 #include "revision.h"
 
 /* Internal API */
@@ -28,8 +27,15 @@ static void graph_padding_line(struct git_graph *graph, struct strbuf *sb);
  * responsible for printing this line's graph (perhaps via
  * graph_show_commit() or graph_show_oneline()) before calling
  * graph_show_strbuf().
+ *
+ * Note that unlike some other graph display functions, you must pass the file
+ * handle directly. It is assumed that this is the same file handle as the
+ * file specified by the graph diff options. This is necessary so that
+ * graph_show_strbuf can be called even with a NULL graph.
  */
-static void graph_show_strbuf(struct git_graph *graph, struct strbuf const *sb);
+static void graph_show_strbuf(struct git_graph *graph,
+			      FILE *file,
+			      struct strbuf const *sb);
 
 /*
  * TODO:
@@ -59,6 +65,17 @@ enum graph_state {
 	GRAPH_COLLAPSING
 };
 
+static void graph_show_line_prefix(const struct diff_options *diffopt)
+{
+	if (!diffopt || !diffopt->line_prefix)
+		return;
+
+	fwrite(diffopt->line_prefix,
+	       sizeof(char),
+	       diffopt->line_prefix_length,
+	       diffopt->file);
+}
+
 static const char **column_colors;
 static unsigned short column_colors_max;
 
@@ -195,14 +212,28 @@ static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void
 	static struct strbuf msgbuf = STRBUF_INIT;
 
 	assert(opt);
-	assert(graph);
 
-	opt->output_prefix_length = graph->width;
 	strbuf_reset(&msgbuf);
-	graph_padding_line(graph, &msgbuf);
+	if (opt->line_prefix)
+		strbuf_add(&msgbuf, opt->line_prefix,
+			   opt->line_prefix_length);
+	if (graph)
+		graph_padding_line(graph, &msgbuf);
 	return &msgbuf;
 }
 
+static const struct diff_options *default_diffopt;
+
+void graph_setup_line_prefix(struct diff_options *diffopt)
+{
+	default_diffopt = diffopt;
+
+	/* setup an output prefix callback if necessary */
+	if (diffopt && !diffopt->output_prefix)
+		diffopt->output_prefix = diff_output_prefix_callback;
+}
+
+
 struct git_graph *graph_init(struct rev_info *opt)
 {
 	struct git_graph *graph = xmalloc(sizeof(struct git_graph));
@@ -245,7 +276,6 @@ struct git_graph *graph_init(struct rev_info *opt)
 	 */
 	opt->diffopt.output_prefix = diff_output_prefix_callback;
 	opt->diffopt.output_prefix_data = graph;
-	opt->diffopt.output_prefix_length = 0;
 
 	return graph;
 }
@@ -1185,6 +1215,8 @@ void graph_show_commit(struct git_graph *graph)
 	struct strbuf msgbuf = STRBUF_INIT;
 	int shown_commit_line = 0;
 
+	graph_show_line_prefix(default_diffopt);
+
 	if (!graph)
 		return;
 
@@ -1202,8 +1234,10 @@ void graph_show_commit(struct git_graph *graph)
 		shown_commit_line = graph_next_line(graph, &msgbuf);
 		fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
 			graph->revs->diffopt.file);
-		if (!shown_commit_line)
+		if (!shown_commit_line) {
 			putc('\n', graph->revs->diffopt.file);
+			graph_show_line_prefix(&graph->revs->diffopt);
+		}
 		strbuf_setlen(&msgbuf, 0);
 	}
 
@@ -1214,6 +1248,8 @@ void graph_show_oneline(struct git_graph *graph)
 {
 	struct strbuf msgbuf = STRBUF_INIT;
 
+	graph_show_line_prefix(default_diffopt);
+
 	if (!graph)
 		return;
 
@@ -1226,6 +1262,8 @@ void graph_show_padding(struct git_graph *graph)
 {
 	struct strbuf msgbuf = STRBUF_INIT;
 
+	graph_show_line_prefix(default_diffopt);
+
 	if (!graph)
 		return;
 
@@ -1239,6 +1277,8 @@ int graph_show_remainder(struct git_graph *graph)
 	struct strbuf msgbuf = STRBUF_INIT;
 	int shown = 0;
 
+	graph_show_line_prefix(default_diffopt);
+
 	if (!graph)
 		return 0;
 
@@ -1252,27 +1292,24 @@ int graph_show_remainder(struct git_graph *graph)
 		strbuf_setlen(&msgbuf, 0);
 		shown = 1;
 
-		if (!graph_is_commit_finished(graph))
+		if (!graph_is_commit_finished(graph)) {
 			putc('\n', graph->revs->diffopt.file);
-		else
+			graph_show_line_prefix(&graph->revs->diffopt);
+		} else {
 			break;
+		}
 	}
 	strbuf_release(&msgbuf);
 
 	return shown;
 }
 
-
-static void graph_show_strbuf(struct git_graph *graph, struct strbuf const *sb)
+static void graph_show_strbuf(struct git_graph *graph,
+			      FILE *file,
+			      struct strbuf const *sb)
 {
 	char *p;
 
-	if (!graph) {
-		fwrite(sb->buf, sizeof(char), sb->len,
-			graph->revs->diffopt.file);
-		return;
-	}
-
 	/*
 	 * Print the strbuf line by line,
 	 * and display the graph info before each line but the first.
@@ -1287,7 +1324,7 @@ static void graph_show_strbuf(struct git_graph *graph, struct strbuf const *sb)
 		} else {
 			len = (sb->buf + sb->len) - p;
 		}
-		fwrite(p, sizeof(char), len, graph->revs->diffopt.file);
+		fwrite(p, sizeof(char), len, file);
 		if (next_p && *next_p != '\0')
 			graph_show_oneline(graph);
 		p = next_p;
@@ -1295,29 +1332,20 @@ static void graph_show_strbuf(struct git_graph *graph, struct strbuf const *sb)
 }
 
 void graph_show_commit_msg(struct git_graph *graph,
+			   FILE *file,
 			   struct strbuf const *sb)
 {
 	int newline_terminated;
 
-	if (!graph) {
-		/*
-		 * If there's no graph, just print the message buffer.
-		 *
-		 * The message buffer for CMIT_FMT_ONELINE and
-		 * CMIT_FMT_USERFORMAT are already missing a terminating
-		 * newline.  All of the other formats should have it.
-		 */
-		fwrite(sb->buf, sizeof(char), sb->len,
-			graph->revs->diffopt.file);
-		return;
-	}
-
-	newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');
-
 	/*
 	 * Show the commit message
 	 */
-	graph_show_strbuf(graph, sb);
+	graph_show_strbuf(graph, file, sb);
+
+	if (!graph)
+		return;
+
+	newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');
 
 	/*
 	 * If there is more output needed for this commit, show it now
@@ -1329,7 +1357,7 @@ void graph_show_commit_msg(struct git_graph *graph,
 		 * new line.
 		 */
 		if (!newline_terminated)
-			putc('\n', graph->revs->diffopt.file);
+			putc('\n', file);
 
 		graph_show_remainder(graph);
 
@@ -1337,6 +1365,6 @@ void graph_show_commit_msg(struct git_graph *graph,
 		 * If sb ends with a newline, our output should too.
 		 */
 		if (newline_terminated)
-			putc('\n', graph->revs->diffopt.file);
+			putc('\n', file);
 	}
 }
diff --git a/graph.h b/graph.h
index 3f48c19b62..af623390b6 100644
--- a/graph.h
+++ b/graph.h
@@ -1,10 +1,23 @@
 #ifndef GRAPH_H
 #define GRAPH_H
+#include "diff.h"
 
 /* A graph is a pointer to this opaque structure */
 struct git_graph;
 
 /*
+ * Called to setup global display of line_prefix diff option.
+ *
+ * Passed a diff_options structure which indicates the line_prefix and the
+ * file to output the prefix to. This is sort of a hack used so that the
+ * line_prefix will be honored by all flows which also honor "--graph"
+ * regardless of whether a graph has actually been setup. The normal graph
+ * flow will honor the exact diff_options passed, but a NULL graph will cause
+ * display of a line_prefix to stdout.
+ */
+void graph_setup_line_prefix(struct diff_options *diffopt);
+
+/*
  * Set up a custom scheme for column colors.
  *
  * The default column color scheme inserts ANSI color escapes to colorize
@@ -113,7 +126,14 @@ int graph_show_remainder(struct git_graph *graph);
  * missing a terminating newline (including if it is empty), the output
  * printed by graph_show_commit_msg() will also be missing a terminating
  * newline.
+ *
+ * Note that unlike some other graph display functions, you must pass the file
+ * handle directly. It is assumed that this is the same file handle as the
+ * file specified by the graph diff options. This is necessary so that
+ * graph_show_commit_msg can be called even with a NULL graph.
  */
-void graph_show_commit_msg(struct git_graph *graph, struct strbuf const *sb);
+void graph_show_commit_msg(struct git_graph *graph,
+			   FILE *file,
+			   struct strbuf const *sb);
 
 #endif /* GRAPH_H */
diff --git a/log-tree.c b/log-tree.c
index bfb735c845..8c2415747a 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -715,10 +715,7 @@ void show_log(struct rev_info *opt)
 	else
 		opt->missing_newline = 0;
 
-	if (opt->graph)
-		graph_show_commit_msg(opt->graph, &msgbuf);
-	else
-		fwrite(msgbuf.buf, sizeof(char), msgbuf.len, opt->diffopt.file);
+	graph_show_commit_msg(opt->graph, opt->diffopt.file, &msgbuf);
 	if (opt->use_terminator && !commit_format_is_empty(opt->commit_format)) {
 		if (!opt->missing_newline)
 			graph_show_padding(opt->graph);
diff --git a/path.c b/path.c
index fe3c4d96c6..a8e72955f6 100644
--- a/path.c
+++ b/path.c
@@ -6,6 +6,7 @@
 #include "string-list.h"
 #include "dir.h"
 #include "worktree.h"
+#include "submodule-config.h"
 
 static int get_st_mode_bits(const char *path, int *mode)
 {
@@ -468,12 +469,16 @@ const char *worktree_git_path(const struct worktree *wt, const char *fmt, ...)
 	return pathname->buf;
 }
 
-static void do_submodule_path(struct strbuf *buf, const char *path,
-			      const char *fmt, va_list args)
+/* Returns 0 on success, negative on failure. */
+#define SUBMODULE_PATH_ERR_NOT_CONFIGURED -1
+static int do_submodule_path(struct strbuf *buf, const char *path,
+			     const char *fmt, va_list args)
 {
 	const char *git_dir;
 	struct strbuf git_submodule_common_dir = STRBUF_INIT;
 	struct strbuf git_submodule_dir = STRBUF_INIT;
+	const struct submodule *sub;
+	int err = 0;
 
 	strbuf_addstr(buf, path);
 	strbuf_complete(buf, '/');
@@ -484,6 +489,17 @@ static void do_submodule_path(struct strbuf *buf, const char *path,
 		strbuf_reset(buf);
 		strbuf_addstr(buf, git_dir);
 	}
+	if (!is_git_directory(buf->buf)) {
+		gitmodules_config();
+		sub = submodule_from_path(null_sha1, path);
+		if (!sub) {
+			err = SUBMODULE_PATH_ERR_NOT_CONFIGURED;
+			goto cleanup;
+		}
+		strbuf_reset(buf);
+		strbuf_git_path(buf, "%s/%s", "modules", sub->name);
+	}
+
 	strbuf_addch(buf, '/');
 	strbuf_addbuf(&git_submodule_dir, buf);
 
@@ -494,27 +510,38 @@ static void do_submodule_path(struct strbuf *buf, const char *path,
 
 	strbuf_cleanup_path(buf);
 
+cleanup:
 	strbuf_release(&git_submodule_dir);
 	strbuf_release(&git_submodule_common_dir);
+
+	return err;
 }
 
 char *git_pathdup_submodule(const char *path, const char *fmt, ...)
 {
+	int err;
 	va_list args;
 	struct strbuf buf = STRBUF_INIT;
 	va_start(args, fmt);
-	do_submodule_path(&buf, path, fmt, args);
+	err = do_submodule_path(&buf, path, fmt, args);
 	va_end(args);
+	if (err) {
+		strbuf_release(&buf);
+		return NULL;
+	}
 	return strbuf_detach(&buf, NULL);
 }
 
-void strbuf_git_path_submodule(struct strbuf *buf, const char *path,
-			       const char *fmt, ...)
+int strbuf_git_path_submodule(struct strbuf *buf, const char *path,
+			      const char *fmt, ...)
 {
+	int err;
 	va_list args;
 	va_start(args, fmt);
-	do_submodule_path(buf, path, fmt, args);
+	err = do_submodule_path(buf, path, fmt, args);
 	va_end(args);
+
+	return err;
 }
 
 static void do_git_common_path(struct strbuf *buf,
diff --git a/refs/files-backend.c b/refs/files-backend.c
index 12290d2496..1f34b444af 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c
@@ -1225,13 +1225,19 @@ static void read_loose_refs(const char *dirname, struct ref_dir *dir)
 	struct strbuf refname;
 	struct strbuf path = STRBUF_INIT;
 	size_t path_baselen;
+	int err = 0;
 
 	if (*refs->name)
-		strbuf_git_path_submodule(&path, refs->name, "%s", dirname);
+		err = strbuf_git_path_submodule(&path, refs->name, "%s", dirname);
 	else
 		strbuf_git_path(&path, "%s", dirname);
 	path_baselen = path.len;
 
+	if (err) {
+		strbuf_release(&path);
+		return;
+	}
+
 	d = opendir(path.buf);
 	if (!d) {
 		strbuf_release(&path);
diff --git a/sha1_file.c b/sha1_file.c
index 6f38dc6548..472ccb2ff9 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -39,6 +39,12 @@ static inline uintmax_t sz_fmt(size_t s) { return s; }
 
 const unsigned char null_sha1[20];
 const struct object_id null_oid;
+const struct object_id empty_tree_oid = {
+	EMPTY_TREE_SHA1_BIN_LITERAL
+};
+const struct object_id empty_blob_oid = {
+	EMPTY_BLOB_SHA1_BIN_LITERAL
+};
 
 /*
  * This is meant to hold a *small* number of objects that you would
diff --git a/submodule.c b/submodule.c
index 1b5cdfb7e7..5a62aa2960 100644
--- a/submodule.c
+++ b/submodule.c
@@ -127,7 +127,9 @@ static int add_submodule_odb(const char *path)
 	int ret = 0;
 	size_t alloc;
 
-	strbuf_git_path_submodule(&objects_directory, path, "objects/");
+	ret = strbuf_git_path_submodule(&objects_directory, path, "objects/");
+	if (ret)
+		goto done;
 	if (!is_directory(objects_directory.buf)) {
 		ret = -1;
 		goto done;
@@ -278,9 +280,9 @@ void handle_ignore_submodules_arg(struct diff_options *diffopt,
 
 static int prepare_submodule_summary(struct rev_info *rev, const char *path,
 		struct commit *left, struct commit *right,
-		int *fast_forward, int *fast_backward)
+		struct commit_list *merge_bases)
 {
-	struct commit_list *merge_bases, *list;
+	struct commit_list *list;
 
 	init_revisions(rev, NULL);
 	setup_revisions(0, NULL, rev, NULL);
@@ -289,13 +291,6 @@ static int prepare_submodule_summary(struct rev_info *rev, const char *path,
 	left->object.flags |= SYMMETRIC_LEFT;
 	add_pending_object(rev, &left->object, path);
 	add_pending_object(rev, &right->object, path);
-	merge_bases = get_merge_bases(left, right);
-	if (merge_bases) {
-		if (merge_bases->item == left)
-			*fast_forward = 1;
-		else if (merge_bases->item == right)
-			*fast_backward = 1;
-	}
 	for (list = merge_bases; list; list = list->next) {
 		list->item->object.flags |= UNINTERESTING;
 		add_pending_object(rev, &list->item->object,
@@ -333,31 +328,23 @@ static void print_submodule_summary(struct rev_info *rev, FILE *f,
 	strbuf_release(&sb);
 }
 
-void show_submodule_summary(FILE *f, const char *path,
+/* Helper function to display the submodule header line prior to the full
+ * summary output. If it can locate the submodule objects directory it will
+ * attempt to lookup both the left and right commits and put them into the
+ * left and right pointers.
+ */
+static void show_submodule_header(FILE *f, const char *path,
 		const char *line_prefix,
-		unsigned char one[20], unsigned char two[20],
+		struct object_id *one, struct object_id *two,
 		unsigned dirty_submodule, const char *meta,
-		const char *del, const char *add, const char *reset)
+		const char *reset,
+		struct commit **left, struct commit **right,
+		struct commit_list **merge_bases)
 {
-	struct rev_info rev;
-	struct commit *left = NULL, *right = NULL;
 	const char *message = NULL;
 	struct strbuf sb = STRBUF_INIT;
 	int fast_forward = 0, fast_backward = 0;
 
-	if (is_null_sha1(two))
-		message = "(submodule deleted)";
-	else if (add_submodule_odb(path))
-		message = "(not checked out)";
-	else if (is_null_sha1(one))
-		message = "(new submodule)";
-	else if (!(left = lookup_commit_reference(one)) ||
-		 !(right = lookup_commit_reference(two)))
-		message = "(commits not present)";
-	else if (prepare_submodule_summary(&rev, path, left, right,
-					   &fast_forward, &fast_backward))
-		message = "(revision walker failed)";
-
 	if (dirty_submodule & DIRTY_SUBMODULE_UNTRACKED)
 		fprintf(f, "%sSubmodule %s contains untracked content\n",
 			line_prefix, path);
@@ -365,30 +352,163 @@ void show_submodule_summary(FILE *f, const char *path,
 		fprintf(f, "%sSubmodule %s contains modified content\n",
 			line_prefix, path);
 
-	if (!hashcmp(one, two)) {
+	if (is_null_oid(one))
+		message = "(new submodule)";
+	else if (is_null_oid(two))
+		message = "(submodule deleted)";
+
+	if (add_submodule_odb(path)) {
+		if (!message)
+			message = "(not initialized)";
+		goto output_header;
+	}
+
+	/*
+	 * Attempt to lookup the commit references, and determine if this is
+	 * a fast forward or fast backwards update.
+	 */
+	*left = lookup_commit_reference(one->hash);
+	*right = lookup_commit_reference(two->hash);
+
+	/*
+	 * Warn about missing commits in the submodule project, but only if
+	 * they aren't null.
+	 */
+	if ((!is_null_oid(one) && !*left) ||
+	     (!is_null_oid(two) && !*right))
+		message = "(commits not present)";
+
+	*merge_bases = get_merge_bases(*left, *right);
+	if (*merge_bases) {
+		if ((*merge_bases)->item == *left)
+			fast_forward = 1;
+		else if ((*merge_bases)->item == *right)
+			fast_backward = 1;
+	}
+
+	if (!oidcmp(one, two)) {
 		strbuf_release(&sb);
 		return;
 	}
 
+output_header:
 	strbuf_addf(&sb, "%s%sSubmodule %s %s..", line_prefix, meta, path,
-			find_unique_abbrev(one, DEFAULT_ABBREV));
+			find_unique_abbrev(one->hash, DEFAULT_ABBREV));
 	if (!fast_backward && !fast_forward)
 		strbuf_addch(&sb, '.');
-	strbuf_addf(&sb, "%s", find_unique_abbrev(two, DEFAULT_ABBREV));
+	strbuf_addf(&sb, "%s", find_unique_abbrev(two->hash, DEFAULT_ABBREV));
 	if (message)
 		strbuf_addf(&sb, " %s%s\n", message, reset);
 	else
 		strbuf_addf(&sb, "%s:%s\n", fast_backward ? " (rewind)" : "", reset);
 	fwrite(sb.buf, sb.len, 1, f);
 
-	if (!message) /* only NULL if we succeeded in setting up the walk */
-		print_submodule_summary(&rev, f, line_prefix, del, add, reset);
+	strbuf_release(&sb);
+}
+
+void show_submodule_summary(FILE *f, const char *path,
+		const char *line_prefix,
+		struct object_id *one, struct object_id *two,
+		unsigned dirty_submodule, const char *meta,
+		const char *del, const char *add, const char *reset)
+{
+	struct rev_info rev;
+	struct commit *left = NULL, *right = NULL;
+	struct commit_list *merge_bases = NULL;
+
+	show_submodule_header(f, path, line_prefix, one, two, dirty_submodule,
+			      meta, reset, &left, &right, &merge_bases);
+
+	/*
+	 * If we don't have both a left and a right pointer, there is no
+	 * reason to try and display a summary. The header line should contain
+	 * all the information the user needs.
+	 */
+	if (!left || !right)
+		goto out;
+
+	/* Treat revision walker failure the same as missing commits */
+	if (prepare_submodule_summary(&rev, path, left, right, merge_bases)) {
+		fprintf(f, "%s(revision walker failed)\n", line_prefix);
+		goto out;
+	}
+
+	print_submodule_summary(&rev, f, line_prefix, del, add, reset);
+
+out:
+	if (merge_bases)
+		free_commit_list(merge_bases);
+	clear_commit_marks(left, ~0);
+	clear_commit_marks(right, ~0);
+}
+
+void show_submodule_inline_diff(FILE *f, const char *path,
+		const char *line_prefix,
+		struct object_id *one, struct object_id *two,
+		unsigned dirty_submodule, const char *meta,
+		const char *del, const char *add, const char *reset,
+		const struct diff_options *o)
+{
+	const struct object_id *old = &empty_tree_oid, *new = &empty_tree_oid;
+	struct commit *left = NULL, *right = NULL;
+	struct commit_list *merge_bases = NULL;
+	struct strbuf submodule_dir = STRBUF_INIT;
+	struct child_process cp = CHILD_PROCESS_INIT;
+
+	show_submodule_header(f, path, line_prefix, one, two, dirty_submodule,
+			      meta, reset, &left, &right, &merge_bases);
+
+	/* We need a valid left and right commit to display a difference */
+	if (!(left || is_null_oid(one)) ||
+	    !(right || is_null_oid(two)))
+		goto done;
+
+	if (left)
+		old = one;
+	if (right)
+		new = two;
+
+	fflush(f);
+	cp.git_cmd = 1;
+	cp.dir = path;
+	cp.out = dup(fileno(f));
+	cp.no_stdin = 1;
+
+	/* TODO: other options may need to be passed here. */
+	argv_array_push(&cp.args, "diff");
+	argv_array_pushf(&cp.args, "--line-prefix=%s", line_prefix);
+	if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
+		argv_array_pushf(&cp.args, "--src-prefix=%s%s/",
+				 o->b_prefix, path);
+		argv_array_pushf(&cp.args, "--dst-prefix=%s%s/",
+				 o->a_prefix, path);
+	} else {
+		argv_array_pushf(&cp.args, "--src-prefix=%s%s/",
+				 o->a_prefix, path);
+		argv_array_pushf(&cp.args, "--dst-prefix=%s%s/",
+				 o->b_prefix, path);
+	}
+	argv_array_push(&cp.args, oid_to_hex(old));
+	/*
+	 * If the submodule has modified content, we will diff against the
+	 * work tree, under the assumption that the user has asked for the
+	 * diff format and wishes to actually see all differences even if they
+	 * haven't yet been committed to the submodule yet.
+	 */
+	if (!(dirty_submodule & DIRTY_SUBMODULE_MODIFIED))
+		argv_array_push(&cp.args, oid_to_hex(new));
+
+	if (run_command(&cp))
+		fprintf(f, "(diff failed)\n");
+
+done:
+	strbuf_release(&submodule_dir);
+	if (merge_bases)
+		free_commit_list(merge_bases);
 	if (left)
 		clear_commit_marks(left, ~0);
 	if (right)
 		clear_commit_marks(right, ~0);
-
-	strbuf_release(&sb);
 }
 
 void set_config_fetch_recurse_submodules(int value)
diff --git a/submodule.h b/submodule.h
index 2af9390998..d9e197a948 100644
--- a/submodule.h
+++ b/submodule.h
@@ -43,9 +43,15 @@ const char *submodule_strategy_to_string(const struct submodule_update_strategy
 void handle_ignore_submodules_arg(struct diff_options *diffopt, const char *);
 void show_submodule_summary(FILE *f, const char *path,
 		const char *line_prefix,
-		unsigned char one[20], unsigned char two[20],
+		struct object_id *one, struct object_id *two,
 		unsigned dirty_submodule, const char *meta,
 		const char *del, const char *add, const char *reset);
+void show_submodule_inline_diff(FILE *f, const char *path,
+		const char *line_prefix,
+		struct object_id *one, struct object_id *two,
+		unsigned dirty_submodule, const char *meta,
+		const char *del, const char *add, const char *reset,
+		const struct diff_options *opt);
 void set_config_fetch_recurse_submodules(int value);
 void check_for_new_submodule_commits(unsigned char new_sha1[20]);
 int fetch_populated_submodules(const struct argv_array *options,
diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 94ef5000e7..566817e2ef 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -306,6 +306,8 @@ diff --no-index --name-status dir2 dir
 diff --no-index --name-status -- dir2 dir
 diff --no-index dir dir3
 diff master master^ side
+# Can't use spaces...
+diff --line-prefix=abc master master^ side
 diff --dirstat master~1 master~2
 diff --dirstat initial rearrange
 diff --dirstat-by-file initial rearrange
@@ -325,6 +327,10 @@ test_expect_success 'diff --cached -- file on unborn branch' '
 	git diff --cached -- file0 >result &&
 	test_cmp "$TEST_DIRECTORY/t4013/diff.diff_--cached_--_file0" result
 '
+test_expect_success 'diff --line-prefix with spaces' '
+	git diff --line-prefix="| | | " --cached -- file0 >result &&
+	test_cmp "$TEST_DIRECTORY/t4013/diff.diff_--line-prefix_--cached_--_file0" result
+'
 
 test_expect_success 'diff-tree --stdin with log formatting' '
 	cat >expect <<-\EOF &&
diff --git a/t/t4013/diff.diff_--line-prefix=abc_master_master^_side b/t/t4013/diff.diff_--line-prefix=abc_master_master^_side
new file mode 100644
index 0000000000..99f91e7f0e
--- /dev/null
+++ b/t/t4013/diff.diff_--line-prefix=abc_master_master^_side
@@ -0,0 +1,29 @@
+$ git diff --line-prefix=abc master master^ side
+abcdiff --cc dir/sub
+abcindex cead32e,7289e35..992913c
+abc--- a/dir/sub
+abc+++ b/dir/sub
+abc@@@ -1,6 -1,4 +1,8 @@@
+abc  A
+abc  B
+abc +C
+abc +D
+abc +E
+abc +F
+abc+ 1
+abc+ 2
+abcdiff --cc file0
+abcindex b414108,f4615da..10a8a9f
+abc--- a/file0
+abc+++ b/file0
+abc@@@ -1,6 -1,6 +1,9 @@@
+abc  1
+abc  2
+abc  3
+abc +4
+abc +5
+abc +6
+abc+ A
+abc+ B
+abc+ C
+$
diff --git a/t/t4013/diff.diff_--line-prefix_--cached_--_file0 b/t/t4013/diff.diff_--line-prefix_--cached_--_file0
new file mode 100644
index 0000000000..f41ba4d36a
--- /dev/null
+++ b/t/t4013/diff.diff_--line-prefix_--cached_--_file0
@@ -0,0 +1,15 @@
+| | | diff --git a/file0 b/file0
+| | | new file mode 100644
+| | | index 0000000..10a8a9f
+| | | --- /dev/null
+| | | +++ b/file0
+| | | @@ -0,0 +1,9 @@
+| | | +1
+| | | +2
+| | | +3
+| | | +4
+| | | +5
+| | | +6
+| | | +A
+| | | +B
+| | | +C
diff --git a/t/t4059-diff-submodule-not-initialized.sh b/t/t4059-diff-submodule-not-initialized.sh
new file mode 100755
index 0000000000..cd70fd5192
--- /dev/null
+++ b/t/t4059-diff-submodule-not-initialized.sh
@@ -0,0 +1,127 @@
+#!/bin/sh
+#
+# Copyright (c) 2016 Jacob Keller, based on t4041 by Jens Lehmann
+#
+
+test_description='Test for submodule diff on non-checked out submodule
+
+This test tries to verify that add_submodule_odb works when the submodule was
+initialized previously but the checkout has since been removed.
+'
+
+. ./test-lib.sh
+
+# Tested non-UTF-8 encoding
+test_encoding="ISO8859-1"
+
+# String "added" in German (translated with Google Translate), encoded in UTF-8,
+# used in sample commit log messages in add_file() function below.
+added=$(printf "hinzugef\303\274gt")
+
+add_file () {
+	(
+		cd "$1" &&
+		shift &&
+		for name
+		do
+			echo "$name" >"$name" &&
+			git add "$name" &&
+			test_tick &&
+			# "git commit -m" would break MinGW, as Windows refuse to pass
+			# $test_encoding encoded parameter to git.
+			echo "Add $name ($added $name)" | iconv -f utf-8 -t $test_encoding |
+			git -c "i18n.commitEncoding=$test_encoding" commit -F -
+		done >/dev/null &&
+		git rev-parse --short --verify HEAD
+	)
+}
+
+commit_file () {
+	test_tick &&
+	git commit "$@" -m "Commit $*" >/dev/null
+}
+
+test_expect_success 'setup - submodules' '
+	test_create_repo sm2 &&
+	add_file . foo &&
+	add_file sm2 foo1 foo2 &&
+	smhead1=$(git -C sm2 rev-parse --short --verify HEAD)
+'
+
+test_expect_success 'setup - git submodule add' '
+	git submodule add ./sm2 sm1 &&
+	commit_file sm1 .gitmodules &&
+	git diff-tree -p --no-commit-id --submodule=log HEAD -- sm1 >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 0000000...$smhead1 (new submodule)
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'submodule directory removed' '
+	rm -rf sm1 &&
+	git diff-tree -p --no-commit-id --submodule=log HEAD -- sm1 >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 0000000...$smhead1 (new submodule)
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'setup - submodule multiple commits' '
+	git submodule update --checkout sm1 &&
+	smhead2=$(add_file sm1 foo3 foo4) &&
+	commit_file sm1 &&
+	git diff-tree -p --no-commit-id --submodule=log HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $smhead1..$smhead2:
+	  > Add foo4 ($added foo4)
+	  > Add foo3 ($added foo3)
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'submodule removed multiple commits' '
+	rm -rf sm1 &&
+	git diff-tree -p --no-commit-id --submodule=log HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $smhead1..$smhead2:
+	  > Add foo4 ($added foo4)
+	  > Add foo3 ($added foo3)
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'submodule not initialized in new clone' '
+	git clone . sm3 &&
+	git -C sm3 diff-tree -p --no-commit-id --submodule=log HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $smhead1...$smhead2 (not initialized)
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'setup submodule moved' '
+	git submodule update --checkout sm1 &&
+	git mv sm1 sm4 &&
+	commit_file sm4 &&
+	git diff-tree -p --no-commit-id --submodule=log HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm4 0000000...$smhead2 (new submodule)
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'submodule moved then removed' '
+	smhead3=$(add_file sm4 foo6 foo7) &&
+	commit_file sm4 &&
+	rm -rf sm4 &&
+	git diff-tree -p --no-commit-id --submodule=log HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm4 $smhead2..$smhead3:
+	  > Add foo7 ($added foo7)
+	  > Add foo6 ($added foo6)
+	EOF
+	test_cmp expected actual
+'
+
+test_done
diff --git a/t/t4060-diff-submodule-option-diff-format.sh b/t/t4060-diff-submodule-option-diff-format.sh
new file mode 100755
index 0000000000..7e23b55ea4
--- /dev/null
+++ b/t/t4060-diff-submodule-option-diff-format.sh
@@ -0,0 +1,749 @@
+#!/bin/sh
+#
+# Copyright (c) 2009 Jens Lehmann, based on t7401 by Ping Yin
+# Copyright (c) 2011 Alexey Shumkin (+ non-UTF-8 commit encoding tests)
+# Copyright (c) 2016 Jacob Keller (copy + convert to --submodule=diff)
+#
+
+test_description='Support for diff format verbose submodule difference in git diff
+
+This test tries to verify the sanity of --submodule=diff option of git diff.
+'
+
+. ./test-lib.sh
+
+# Tested non-UTF-8 encoding
+test_encoding="ISO8859-1"
+
+# String "added" in German (translated with Google Translate), encoded in UTF-8,
+# used in sample commit log messages in add_file() function below.
+added=$(printf "hinzugef\303\274gt")
+
+add_file () {
+	(
+		cd "$1" &&
+		shift &&
+		for name
+		do
+			echo "$name" >"$name" &&
+			git add "$name" &&
+			test_tick &&
+			# "git commit -m" would break MinGW, as Windows refuse to pass
+			# $test_encoding encoded parameter to git.
+			echo "Add $name ($added $name)" | iconv -f utf-8 -t $test_encoding |
+			git -c "i18n.commitEncoding=$test_encoding" commit -F -
+		done >/dev/null &&
+		git rev-parse --short --verify HEAD
+	)
+}
+
+commit_file () {
+	test_tick &&
+	git commit "$@" -m "Commit $*" >/dev/null
+}
+
+test_expect_success 'setup repository' '
+	test_create_repo sm1 &&
+	add_file . foo &&
+	head1=$(add_file sm1 foo1 foo2) &&
+	fullhead1=$(git -C sm1 rev-parse --verify HEAD)
+'
+
+test_expect_success 'added submodule' '
+	git add sm1 &&
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 0000000...$head1 (new submodule)
+	diff --git a/sm1/foo1 b/sm1/foo1
+	new file mode 100644
+	index 0000000..1715acd
+	--- /dev/null
+	+++ b/sm1/foo1
+	@@ -0,0 +1 @@
+	+foo1
+	diff --git a/sm1/foo2 b/sm1/foo2
+	new file mode 100644
+	index 0000000..54b060e
+	--- /dev/null
+	+++ b/sm1/foo2
+	@@ -0,0 +1 @@
+	+foo2
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'added submodule, set diff.submodule' '
+	test_config diff.submodule log &&
+	git add sm1 &&
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 0000000...$head1 (new submodule)
+	diff --git a/sm1/foo1 b/sm1/foo1
+	new file mode 100644
+	index 0000000..1715acd
+	--- /dev/null
+	+++ b/sm1/foo1
+	@@ -0,0 +1 @@
+	+foo1
+	diff --git a/sm1/foo2 b/sm1/foo2
+	new file mode 100644
+	index 0000000..54b060e
+	--- /dev/null
+	+++ b/sm1/foo2
+	@@ -0,0 +1 @@
+	+foo2
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success '--submodule=short overrides diff.submodule' '
+	test_config diff.submodule log &&
+	git add sm1 &&
+	git diff --submodule=short --cached >actual &&
+	cat >expected <<-EOF &&
+	diff --git a/sm1 b/sm1
+	new file mode 160000
+	index 0000000..$head1
+	--- /dev/null
+	+++ b/sm1
+	@@ -0,0 +1 @@
+	+Subproject commit $fullhead1
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'diff.submodule does not affect plumbing' '
+	test_config diff.submodule log &&
+	git diff-index -p HEAD >actual &&
+	cat >expected <<-EOF &&
+	diff --git a/sm1 b/sm1
+	new file mode 160000
+	index 0000000..$head1
+	--- /dev/null
+	+++ b/sm1
+	@@ -0,0 +1 @@
+	+Subproject commit $fullhead1
+	EOF
+	test_cmp expected actual
+'
+
+commit_file sm1 &&
+head2=$(add_file sm1 foo3)
+
+test_expect_success 'modified submodule(forward)' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $head1..$head2:
+	diff --git a/sm1/foo3 b/sm1/foo3
+	new file mode 100644
+	index 0000000..c1ec6c6
+	--- /dev/null
+	+++ b/sm1/foo3
+	@@ -0,0 +1 @@
+	+foo3
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'modified submodule(forward)' '
+	git diff --submodule=diff >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $head1..$head2:
+	diff --git a/sm1/foo3 b/sm1/foo3
+	new file mode 100644
+	index 0000000..c1ec6c6
+	--- /dev/null
+	+++ b/sm1/foo3
+	@@ -0,0 +1 @@
+	+foo3
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'modified submodule(forward) --submodule' '
+	git diff --submodule >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $head1..$head2:
+	  > Add foo3 ($added foo3)
+	EOF
+	test_cmp expected actual
+'
+
+fullhead2=$(cd sm1; git rev-parse --verify HEAD)
+test_expect_success 'modified submodule(forward) --submodule=short' '
+	git diff --submodule=short >actual &&
+	cat >expected <<-EOF &&
+	diff --git a/sm1 b/sm1
+	index $head1..$head2 160000
+	--- a/sm1
+	+++ b/sm1
+	@@ -1 +1 @@
+	-Subproject commit $fullhead1
+	+Subproject commit $fullhead2
+	EOF
+	test_cmp expected actual
+'
+
+commit_file sm1 &&
+head3=$(
+	cd sm1 &&
+	git reset --hard HEAD~2 >/dev/null &&
+	git rev-parse --short --verify HEAD
+)
+
+test_expect_success 'modified submodule(backward)' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $head2..$head3 (rewind):
+	diff --git a/sm1/foo2 b/sm1/foo2
+	deleted file mode 100644
+	index 54b060e..0000000
+	--- a/sm1/foo2
+	+++ /dev/null
+	@@ -1 +0,0 @@
+	-foo2
+	diff --git a/sm1/foo3 b/sm1/foo3
+	deleted file mode 100644
+	index c1ec6c6..0000000
+	--- a/sm1/foo3
+	+++ /dev/null
+	@@ -1 +0,0 @@
+	-foo3
+	EOF
+	test_cmp expected actual
+'
+
+head4=$(add_file sm1 foo4 foo5)
+test_expect_success 'modified submodule(backward and forward)' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $head2...$head4:
+	diff --git a/sm1/foo2 b/sm1/foo2
+	deleted file mode 100644
+	index 54b060e..0000000
+	--- a/sm1/foo2
+	+++ /dev/null
+	@@ -1 +0,0 @@
+	-foo2
+	diff --git a/sm1/foo3 b/sm1/foo3
+	deleted file mode 100644
+	index c1ec6c6..0000000
+	--- a/sm1/foo3
+	+++ /dev/null
+	@@ -1 +0,0 @@
+	-foo3
+	diff --git a/sm1/foo4 b/sm1/foo4
+	new file mode 100644
+	index 0000000..a0016db
+	--- /dev/null
+	+++ b/sm1/foo4
+	@@ -0,0 +1 @@
+	+foo4
+	diff --git a/sm1/foo5 b/sm1/foo5
+	new file mode 100644
+	index 0000000..d6f2413
+	--- /dev/null
+	+++ b/sm1/foo5
+	@@ -0,0 +1 @@
+	+foo5
+	EOF
+	test_cmp expected actual
+'
+
+commit_file sm1 &&
+mv sm1 sm1-bak &&
+echo sm1 >sm1 &&
+head5=$(git hash-object sm1 | cut -c1-7) &&
+git add sm1 &&
+rm -f sm1 &&
+mv sm1-bak sm1
+
+test_expect_success 'typechanged submodule(submodule->blob), --cached' '
+	git diff --submodule=diff --cached >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $head4...0000000 (submodule deleted)
+	diff --git a/sm1/foo1 b/sm1/foo1
+	deleted file mode 100644
+	index 1715acd..0000000
+	--- a/sm1/foo1
+	+++ /dev/null
+	@@ -1 +0,0 @@
+	-foo1
+	diff --git a/sm1/foo4 b/sm1/foo4
+	deleted file mode 100644
+	index a0016db..0000000
+	--- a/sm1/foo4
+	+++ /dev/null
+	@@ -1 +0,0 @@
+	-foo4
+	diff --git a/sm1/foo5 b/sm1/foo5
+	deleted file mode 100644
+	index d6f2413..0000000
+	--- a/sm1/foo5
+	+++ /dev/null
+	@@ -1 +0,0 @@
+	-foo5
+	diff --git a/sm1 b/sm1
+	new file mode 100644
+	index 0000000..9da5fb8
+	--- /dev/null
+	+++ b/sm1
+	@@ -0,0 +1 @@
+	+sm1
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'typechanged submodule(submodule->blob)' '
+	git diff --submodule=diff >actual &&
+	cat >expected <<-EOF &&
+	diff --git a/sm1 b/sm1
+	deleted file mode 100644
+	index 9da5fb8..0000000
+	--- a/sm1
+	+++ /dev/null
+	@@ -1 +0,0 @@
+	-sm1
+	Submodule sm1 0000000...$head4 (new submodule)
+	diff --git a/sm1/foo1 b/sm1/foo1
+	new file mode 100644
+	index 0000000..1715acd
+	--- /dev/null
+	+++ b/sm1/foo1
+	@@ -0,0 +1 @@
+	+foo1
+	diff --git a/sm1/foo4 b/sm1/foo4
+	new file mode 100644
+	index 0000000..a0016db
+	--- /dev/null
+	+++ b/sm1/foo4
+	@@ -0,0 +1 @@
+	+foo4
+	diff --git a/sm1/foo5 b/sm1/foo5
+	new file mode 100644
+	index 0000000..d6f2413
+	--- /dev/null
+	+++ b/sm1/foo5
+	@@ -0,0 +1 @@
+	+foo5
+	EOF
+	test_cmp expected actual
+'
+
+rm -rf sm1 &&
+git checkout-index sm1
+test_expect_success 'typechanged submodule(submodule->blob)' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $head4...0000000 (submodule deleted)
+	diff --git a/sm1 b/sm1
+	new file mode 100644
+	index 0000000..9da5fb8
+	--- /dev/null
+	+++ b/sm1
+	@@ -0,0 +1 @@
+	+sm1
+	EOF
+	test_cmp expected actual
+'
+
+rm -f sm1 &&
+test_create_repo sm1 &&
+head6=$(add_file sm1 foo6 foo7)
+fullhead6=$(cd sm1; git rev-parse --verify HEAD)
+test_expect_success 'nonexistent commit' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 $head4...$head6 (commits not present)
+	EOF
+	test_cmp expected actual
+'
+
+commit_file
+test_expect_success 'typechanged submodule(blob->submodule)' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	diff --git a/sm1 b/sm1
+	deleted file mode 100644
+	index 9da5fb8..0000000
+	--- a/sm1
+	+++ /dev/null
+	@@ -1 +0,0 @@
+	-sm1
+	Submodule sm1 0000000...$head6 (new submodule)
+	diff --git a/sm1/foo6 b/sm1/foo6
+	new file mode 100644
+	index 0000000..462398b
+	--- /dev/null
+	+++ b/sm1/foo6
+	@@ -0,0 +1 @@
+	+foo6
+	diff --git a/sm1/foo7 b/sm1/foo7
+	new file mode 100644
+	index 0000000..6e9262c
+	--- /dev/null
+	+++ b/sm1/foo7
+	@@ -0,0 +1 @@
+	+foo7
+	EOF
+	test_cmp expected actual
+'
+
+commit_file sm1 &&
+test_expect_success 'submodule is up to date' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'submodule contains untracked content' '
+	echo new > sm1/new-file &&
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 contains untracked content
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'submodule contains untracked content (untracked ignored)' '
+	git diff-index -p --ignore-submodules=untracked --submodule=diff HEAD >actual &&
+	! test -s actual
+'
+
+test_expect_success 'submodule contains untracked content (dirty ignored)' '
+	git diff-index -p --ignore-submodules=dirty --submodule=diff HEAD >actual &&
+	! test -s actual
+'
+
+test_expect_success 'submodule contains untracked content (all ignored)' '
+	git diff-index -p --ignore-submodules=all --submodule=diff HEAD >actual &&
+	! test -s actual
+'
+
+test_expect_success 'submodule contains untracked and modified content' '
+	echo new > sm1/foo6 &&
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 contains untracked content
+	Submodule sm1 contains modified content
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..3e75765 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1 @@
+	-foo6
+	+new
+	EOF
+	test_cmp expected actual
+'
+
+# NOT OK
+test_expect_success 'submodule contains untracked and modified content (untracked ignored)' '
+	echo new > sm1/foo6 &&
+	git diff-index -p --ignore-submodules=untracked --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 contains modified content
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..3e75765 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1 @@
+	-foo6
+	+new
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'submodule contains untracked and modified content (dirty ignored)' '
+	echo new > sm1/foo6 &&
+	git diff-index -p --ignore-submodules=dirty --submodule=diff HEAD >actual &&
+	! test -s actual
+'
+
+test_expect_success 'submodule contains untracked and modified content (all ignored)' '
+	echo new > sm1/foo6 &&
+	git diff-index -p --ignore-submodules --submodule=diff HEAD >actual &&
+	! test -s actual
+'
+
+test_expect_success 'submodule contains modified content' '
+	rm -f sm1/new-file &&
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 contains modified content
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..3e75765 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1 @@
+	-foo6
+	+new
+	EOF
+	test_cmp expected actual
+'
+
+(cd sm1; git commit -mchange foo6 >/dev/null) &&
+head8=$(cd sm1; git rev-parse --short --verify HEAD) &&
+test_expect_success 'submodule is modified' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 17243c9..$head8:
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..3e75765 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1 @@
+	-foo6
+	+new
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'modified submodule contains untracked content' '
+	echo new > sm1/new-file &&
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 contains untracked content
+	Submodule sm1 17243c9..$head8:
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..3e75765 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1 @@
+	-foo6
+	+new
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'modified submodule contains untracked content (untracked ignored)' '
+	git diff-index -p --ignore-submodules=untracked --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 17243c9..$head8:
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..3e75765 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1 @@
+	-foo6
+	+new
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'modified submodule contains untracked content (dirty ignored)' '
+	git diff-index -p --ignore-submodules=dirty --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 17243c9..cfce562:
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..3e75765 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1 @@
+	-foo6
+	+new
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'modified submodule contains untracked content (all ignored)' '
+	git diff-index -p --ignore-submodules=all --submodule=diff HEAD >actual &&
+	! test -s actual
+'
+
+test_expect_success 'modified submodule contains untracked and modified content' '
+	echo modification >> sm1/foo6 &&
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 contains untracked content
+	Submodule sm1 contains modified content
+	Submodule sm1 17243c9..cfce562:
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..dfda541 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1,2 @@
+	-foo6
+	+new
+	+modification
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'modified submodule contains untracked and modified content (untracked ignored)' '
+	echo modification >> sm1/foo6 &&
+	git diff-index -p --ignore-submodules=untracked --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 contains modified content
+	Submodule sm1 17243c9..cfce562:
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..e20e2d9 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1,3 @@
+	-foo6
+	+new
+	+modification
+	+modification
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'modified submodule contains untracked and modified content (dirty ignored)' '
+	echo modification >> sm1/foo6 &&
+	git diff-index -p --ignore-submodules=dirty --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 17243c9..cfce562:
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..3e75765 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1 @@
+	-foo6
+	+new
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'modified submodule contains untracked and modified content (all ignored)' '
+	echo modification >> sm1/foo6 &&
+	git diff-index -p --ignore-submodules --submodule=diff HEAD >actual &&
+	! test -s actual
+'
+
+# NOT OK
+test_expect_success 'modified submodule contains modified content' '
+	rm -f sm1/new-file &&
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 contains modified content
+	Submodule sm1 17243c9..cfce562:
+	diff --git a/sm1/foo6 b/sm1/foo6
+	index 462398b..ac466ca 100644
+	--- a/sm1/foo6
+	+++ b/sm1/foo6
+	@@ -1 +1,5 @@
+	-foo6
+	+new
+	+modification
+	+modification
+	+modification
+	+modification
+	EOF
+	test_cmp expected actual
+'
+
+rm -rf sm1
+test_expect_success 'deleted submodule' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 17243c9...0000000 (submodule deleted)
+	EOF
+	test_cmp expected actual
+'
+
+test_create_repo sm2 &&
+head7=$(add_file sm2 foo8 foo9) &&
+git add sm2
+
+test_expect_success 'multiple submodules' '
+	git diff-index -p --submodule=diff HEAD >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 17243c9...0000000 (submodule deleted)
+	Submodule sm2 0000000...a5a65c9 (new submodule)
+	diff --git a/sm2/foo8 b/sm2/foo8
+	new file mode 100644
+	index 0000000..db9916b
+	--- /dev/null
+	+++ b/sm2/foo8
+	@@ -0,0 +1 @@
+	+foo8
+	diff --git a/sm2/foo9 b/sm2/foo9
+	new file mode 100644
+	index 0000000..9c3b4f6
+	--- /dev/null
+	+++ b/sm2/foo9
+	@@ -0,0 +1 @@
+	+foo9
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'path filter' '
+	git diff-index -p --submodule=diff HEAD sm2 >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm2 0000000...a5a65c9 (new submodule)
+	diff --git a/sm2/foo8 b/sm2/foo8
+	new file mode 100644
+	index 0000000..db9916b
+	--- /dev/null
+	+++ b/sm2/foo8
+	@@ -0,0 +1 @@
+	+foo8
+	diff --git a/sm2/foo9 b/sm2/foo9
+	new file mode 100644
+	index 0000000..9c3b4f6
+	--- /dev/null
+	+++ b/sm2/foo9
+	@@ -0,0 +1 @@
+	+foo9
+	EOF
+	test_cmp expected actual
+'
+
+commit_file sm2
+test_expect_success 'given commit' '
+	git diff-index -p --submodule=diff HEAD^ >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 17243c9...0000000 (submodule deleted)
+	Submodule sm2 0000000...a5a65c9 (new submodule)
+	diff --git a/sm2/foo8 b/sm2/foo8
+	new file mode 100644
+	index 0000000..db9916b
+	--- /dev/null
+	+++ b/sm2/foo8
+	@@ -0,0 +1 @@
+	+foo8
+	diff --git a/sm2/foo9 b/sm2/foo9
+	new file mode 100644
+	index 0000000..9c3b4f6
+	--- /dev/null
+	+++ b/sm2/foo9
+	@@ -0,0 +1 @@
+	+foo9
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'setup .git file for sm2' '
+	(cd sm2 &&
+	 REAL="$(pwd)/../.real" &&
+	 mv .git "$REAL"
+	 echo "gitdir: $REAL" >.git)
+'
+
+test_expect_success 'diff --submodule=diff with .git file' '
+	git diff --submodule=diff HEAD^ >actual &&
+	cat >expected <<-EOF &&
+	Submodule sm1 17243c9...0000000 (submodule deleted)
+	Submodule sm2 0000000...a5a65c9 (new submodule)
+	diff --git a/sm2/foo8 b/sm2/foo8
+	new file mode 100644
+	index 0000000..db9916b
+	--- /dev/null
+	+++ b/sm2/foo8
+	@@ -0,0 +1 @@
+	+foo8
+	diff --git a/sm2/foo9 b/sm2/foo9
+	new file mode 100644
+	index 0000000..9c3b4f6
+	--- /dev/null
+	+++ b/sm2/foo9
+	@@ -0,0 +1 @@
+	+foo9
+	EOF
+	test_cmp expected actual
+'
+
+test_done
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index e2db47c36e..1ccbd5948a 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -188,6 +188,16 @@ test_expect_success 'git log --no-walk=sorted <commits> sorts by commit time' '
 '
 
 cat > expect << EOF
+=== 804a787 sixth
+=== 394ef78 fifth
+=== 5d31159 fourth
+EOF
+test_expect_success 'git log --line-prefix="=== " --no-walk <commits> sorts by commit time' '
+	git log --line-prefix="=== " --no-walk --oneline 5d31159 804a787 394ef78 > actual &&
+	test_cmp expect actual
+'
+
+cat > expect << EOF
 5d31159 fourth
 804a787 sixth
 394ef78 fifth
@@ -284,6 +294,21 @@ test_expect_success 'simple log --graph' '
 	test_cmp expect actual
 '
 
+cat > expect <<EOF
+123 * Second
+123 * sixth
+123 * fifth
+123 * fourth
+123 * third
+123 * second
+123 * initial
+EOF
+
+test_expect_success 'simple log --graph --line-prefix="123 "' '
+	git log --graph --line-prefix="123 " --pretty=tformat:%s >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'set up merge history' '
 	git checkout -b side HEAD~4 &&
 	test_commit side-1 1 1 &&
@@ -313,6 +338,27 @@ test_expect_success 'log --graph with merge' '
 	test_cmp expect actual
 '
 
+cat > expect <<\EOF
+| | | *   Merge branch 'side'
+| | | |\
+| | | | * side-2
+| | | | * side-1
+| | | * | Second
+| | | * | sixth
+| | | * | fifth
+| | | * | fourth
+| | | |/
+| | | * third
+| | | * second
+| | | * initial
+EOF
+
+test_expect_success 'log --graph --line-prefix="| | | " with merge' '
+	git log --line-prefix="| | | " --graph --date-order --pretty=tformat:%s |
+		sed "s/ *\$//" >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'log --raw --graph -m with merge' '
 	git log --raw --graph --oneline -m master | head -n 500 >actual &&
 	grep "initial" actual
@@ -867,6 +913,283 @@ test_expect_success 'log --graph with diff and stats' '
 	test_i18ncmp expect actual.sanitized
 '
 
+cat >expect <<\EOF
+*** *   commit COMMIT_OBJECT_NAME
+*** |\  Merge: MERGE_PARENTS
+*** | | Author: A U Thor <author@example.com>
+*** | |
+*** | |     Merge HEADS DESCRIPTION
+*** | |
+*** | * commit COMMIT_OBJECT_NAME
+*** | | Author: A U Thor <author@example.com>
+*** | |
+*** | |     reach
+*** | | ---
+*** | |  reach.t | 1 +
+*** | |  1 file changed, 1 insertion(+)
+*** | |
+*** | | diff --git a/reach.t b/reach.t
+*** | | new file mode 100644
+*** | | index 0000000..10c9591
+*** | | --- /dev/null
+*** | | +++ b/reach.t
+*** | | @@ -0,0 +1 @@
+*** | | +reach
+*** | |
+*** |  \
+*** *-. \   commit COMMIT_OBJECT_NAME
+*** |\ \ \  Merge: MERGE_PARENTS
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     Merge HEADS DESCRIPTION
+*** | | | |
+*** | | * | commit COMMIT_OBJECT_NAME
+*** | | |/  Author: A U Thor <author@example.com>
+*** | | |
+*** | | |       octopus-b
+*** | | |   ---
+*** | | |    octopus-b.t | 1 +
+*** | | |    1 file changed, 1 insertion(+)
+*** | | |
+*** | | |   diff --git a/octopus-b.t b/octopus-b.t
+*** | | |   new file mode 100644
+*** | | |   index 0000000..d5fcad0
+*** | | |   --- /dev/null
+*** | | |   +++ b/octopus-b.t
+*** | | |   @@ -0,0 +1 @@
+*** | | |   +octopus-b
+*** | | |
+*** | * | commit COMMIT_OBJECT_NAME
+*** | |/  Author: A U Thor <author@example.com>
+*** | |
+*** | |       octopus-a
+*** | |   ---
+*** | |    octopus-a.t | 1 +
+*** | |    1 file changed, 1 insertion(+)
+*** | |
+*** | |   diff --git a/octopus-a.t b/octopus-a.t
+*** | |   new file mode 100644
+*** | |   index 0000000..11ee015
+*** | |   --- /dev/null
+*** | |   +++ b/octopus-a.t
+*** | |   @@ -0,0 +1 @@
+*** | |   +octopus-a
+*** | |
+*** * | commit COMMIT_OBJECT_NAME
+*** |/  Author: A U Thor <author@example.com>
+*** |
+*** |       seventh
+*** |   ---
+*** |    seventh.t | 1 +
+*** |    1 file changed, 1 insertion(+)
+*** |
+*** |   diff --git a/seventh.t b/seventh.t
+*** |   new file mode 100644
+*** |   index 0000000..9744ffc
+*** |   --- /dev/null
+*** |   +++ b/seventh.t
+*** |   @@ -0,0 +1 @@
+*** |   +seventh
+*** |
+*** *   commit COMMIT_OBJECT_NAME
+*** |\  Merge: MERGE_PARENTS
+*** | | Author: A U Thor <author@example.com>
+*** | |
+*** | |     Merge branch 'tangle'
+*** | |
+*** | *   commit COMMIT_OBJECT_NAME
+*** | |\  Merge: MERGE_PARENTS
+*** | | | Author: A U Thor <author@example.com>
+*** | | |
+*** | | |     Merge branch 'side' (early part) into tangle
+*** | | |
+*** | * |   commit COMMIT_OBJECT_NAME
+*** | |\ \  Merge: MERGE_PARENTS
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     Merge branch 'master' (early part) into tangle
+*** | | | |
+*** | * | | commit COMMIT_OBJECT_NAME
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     tangle-a
+*** | | | | ---
+*** | | | |  tangle-a | 1 +
+*** | | | |  1 file changed, 1 insertion(+)
+*** | | | |
+*** | | | | diff --git a/tangle-a b/tangle-a
+*** | | | | new file mode 100644
+*** | | | | index 0000000..7898192
+*** | | | | --- /dev/null
+*** | | | | +++ b/tangle-a
+*** | | | | @@ -0,0 +1 @@
+*** | | | | +a
+*** | | | |
+*** * | | |   commit COMMIT_OBJECT_NAME
+*** |\ \ \ \  Merge: MERGE_PARENTS
+*** | | | | | Author: A U Thor <author@example.com>
+*** | | | | |
+*** | | | | |     Merge branch 'side'
+*** | | | | |
+*** | * | | | commit COMMIT_OBJECT_NAME
+*** | | |_|/  Author: A U Thor <author@example.com>
+*** | |/| |
+*** | | | |       side-2
+*** | | | |   ---
+*** | | | |    2 | 1 +
+*** | | | |    1 file changed, 1 insertion(+)
+*** | | | |
+*** | | | |   diff --git a/2 b/2
+*** | | | |   new file mode 100644
+*** | | | |   index 0000000..0cfbf08
+*** | | | |   --- /dev/null
+*** | | | |   +++ b/2
+*** | | | |   @@ -0,0 +1 @@
+*** | | | |   +2
+*** | | | |
+*** | * | | commit COMMIT_OBJECT_NAME
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     side-1
+*** | | | | ---
+*** | | | |  1 | 1 +
+*** | | | |  1 file changed, 1 insertion(+)
+*** | | | |
+*** | | | | diff --git a/1 b/1
+*** | | | | new file mode 100644
+*** | | | | index 0000000..d00491f
+*** | | | | --- /dev/null
+*** | | | | +++ b/1
+*** | | | | @@ -0,0 +1 @@
+*** | | | | +1
+*** | | | |
+*** * | | | commit COMMIT_OBJECT_NAME
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     Second
+*** | | | | ---
+*** | | | |  one | 1 +
+*** | | | |  1 file changed, 1 insertion(+)
+*** | | | |
+*** | | | | diff --git a/one b/one
+*** | | | | new file mode 100644
+*** | | | | index 0000000..9a33383
+*** | | | | --- /dev/null
+*** | | | | +++ b/one
+*** | | | | @@ -0,0 +1 @@
+*** | | | | +case
+*** | | | |
+*** * | | | commit COMMIT_OBJECT_NAME
+*** | |_|/  Author: A U Thor <author@example.com>
+*** |/| |
+*** | | |       sixth
+*** | | |   ---
+*** | | |    a/two | 1 -
+*** | | |    1 file changed, 1 deletion(-)
+*** | | |
+*** | | |   diff --git a/a/two b/a/two
+*** | | |   deleted file mode 100644
+*** | | |   index 9245af5..0000000
+*** | | |   --- a/a/two
+*** | | |   +++ /dev/null
+*** | | |   @@ -1 +0,0 @@
+*** | | |   -ni
+*** | | |
+*** * | | commit COMMIT_OBJECT_NAME
+*** | | | Author: A U Thor <author@example.com>
+*** | | |
+*** | | |     fifth
+*** | | | ---
+*** | | |  a/two | 1 +
+*** | | |  1 file changed, 1 insertion(+)
+*** | | |
+*** | | | diff --git a/a/two b/a/two
+*** | | | new file mode 100644
+*** | | | index 0000000..9245af5
+*** | | | --- /dev/null
+*** | | | +++ b/a/two
+*** | | | @@ -0,0 +1 @@
+*** | | | +ni
+*** | | |
+*** * | | commit COMMIT_OBJECT_NAME
+*** |/ /  Author: A U Thor <author@example.com>
+*** | |
+*** | |       fourth
+*** | |   ---
+*** | |    ein | 1 +
+*** | |    1 file changed, 1 insertion(+)
+*** | |
+*** | |   diff --git a/ein b/ein
+*** | |   new file mode 100644
+*** | |   index 0000000..9d7e69f
+*** | |   --- /dev/null
+*** | |   +++ b/ein
+*** | |   @@ -0,0 +1 @@
+*** | |   +ichi
+*** | |
+*** * | commit COMMIT_OBJECT_NAME
+*** |/  Author: A U Thor <author@example.com>
+*** |
+*** |       third
+*** |   ---
+*** |    ichi | 1 +
+*** |    one  | 1 -
+*** |    2 files changed, 1 insertion(+), 1 deletion(-)
+*** |
+*** |   diff --git a/ichi b/ichi
+*** |   new file mode 100644
+*** |   index 0000000..9d7e69f
+*** |   --- /dev/null
+*** |   +++ b/ichi
+*** |   @@ -0,0 +1 @@
+*** |   +ichi
+*** |   diff --git a/one b/one
+*** |   deleted file mode 100644
+*** |   index 9d7e69f..0000000
+*** |   --- a/one
+*** |   +++ /dev/null
+*** |   @@ -1 +0,0 @@
+*** |   -ichi
+*** |
+*** * commit COMMIT_OBJECT_NAME
+*** | Author: A U Thor <author@example.com>
+*** |
+*** |     second
+*** | ---
+*** |  one | 2 +-
+*** |  1 file changed, 1 insertion(+), 1 deletion(-)
+*** |
+*** | diff --git a/one b/one
+*** | index 5626abf..9d7e69f 100644
+*** | --- a/one
+*** | +++ b/one
+*** | @@ -1 +1 @@
+*** | -one
+*** | +ichi
+*** |
+*** * commit COMMIT_OBJECT_NAME
+***   Author: A U Thor <author@example.com>
+***
+***       initial
+***   ---
+***    one | 1 +
+***    1 file changed, 1 insertion(+)
+***
+***   diff --git a/one b/one
+***   new file mode 100644
+***   index 0000000..5626abf
+***   --- /dev/null
+***   +++ b/one
+***   @@ -0,0 +1 @@
+***   +one
+EOF
+
+test_expect_success 'log --line-prefix="*** " --graph with diff and stats' '
+	git log --line-prefix="*** " --no-renames --graph --pretty=short --stat -p >actual &&
+	sanitize_output >actual.sanitized <actual &&
+	test_i18ncmp expect actual.sanitized
+'
+
 test_expect_success 'dotdot is a parent directory' '
 	mkdir -p a/b &&
 	( echo sixth && echo fifth ) >expect &&